- Synthesis, structure and catalytic activity of an oxo-bridged dinuclear oxovanadium complex of an isonicotinohydrazide ligand
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A mononuclear dioxo vanadium(V) complex of a hydrazone ONO donor ligand, [VVO2(L1)] (1), was synthesized by the reaction of V2O5 and terephthalic acid with H2L 1 in 1:1:1 mol ratio, while an oxo-bridged bis(vanadium(IV)oxo) complex, [μ 2-O-{VIVO(L2)}2] (2), was synthesized by the treatment of isonicotinic acid hydrazide, salicylaldehyde and CoSO4·7H2O with bis(acetylacetonato)oxovanadium(IV) (H2L1 = isonicotinic acid(2-hydroxy-benzylidene)-hydrazide, H2L2 = isonicotinic acid (1-methyl-3-oxo-butylidene)-hydrazide). The complexes were characterized by elemental analyses and spectroscopic methods. The crystal structure of complex 2 was determined by X-ray analysis. The complexes were tested as catalysts for the oxidation of cycloalkenes and benzyl alcohol using H 2O2 as terminal oxidant. Excellent selectivity was achieved in the oxidation of cyclohexene.
- Hosseini-Monfared, Hassan,Farrokhi, Afsaneh,Alavi, Sohaila,Mayer, Peter
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- Oxidation of alkenes with hydrogen peroxide, catalyzed by boron trifluoride. Synthesis of vicinal methoxyalkanols
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In oxidation of alkenes with the BF3-H2O2 system, boron trifluoride induces transfer of available oxygen from hydrogen peroxide, accompanied by the formation of epoxides. The oxidation in methanol occurs as a one-pot two-step process involving epoxidation of the C=C bond followed by opening of the oxirane ring, with the formation of methoxyalkanols.
- Terent'ev,Boyarinova,Nikishin
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- Epoxidation of cyclohexene with molecular oxygen by electrolysis combined with chemical catalysis
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This paper describes an electrochemical coupling epoxidation of cyclohexene by molecular oxygen (O2) under mild reaction conditions. Herein, the electroreduction of O2 to hydrogen peroxide (H2O2) efficiently proceeds in a relatively environmentally friendly acetone/water medium containing electrolytes at 25-30 °C on a self-assembled H type of electrolysis cell with tree electrodes system, providing ca. 44.3 mM concentration of H2O2 under the optimal electrolysis conditions. The epoxidation of cyclohexene with in situ generated H2O2 simultaneously occurs upon catalysis by metal complexes, giving ca. 19.8 % of cyclohexene conversion with 78 % of epoxidative selectivity over the best catalyst 5-Cl-7-I-8-quinolinolato manganese(III) complex (Q3MnIII (e)). The present electrochemical coupling epoxidation result is nearly equivalent to the epoxidation of cyclohexene with adscititious H2O2 catalyzed by the Q3MnIII (e).
- Wang, Yanlong,Deng, Jie,Zhang, Chao,Wu, Wenfeng,Xie, Qingji,Liu, Yachun,Fu, Zaihui
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- Styrene-hydroxyethyl methacrylate copolymer microsphere immobilized porphyrinatomanganese(III) as a mild, reusable and highly efficient catalyst for epoxidation of cyclohexene with molecular oxygen
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On the basis of synthesis of styrene-hydroxyethyl methacrylate copolymer microspheres with a functionalized hydroxyl, we have prepared a new type of copolymer microspheres immobilized porphyrinatomanganese(III), P(St-co-HEMA)MnP, by a condensation reactio
- Ye, Yuan-Jian,Zhou, Xian-Tai,Huang, Jin-Wang,Cai, Jin-Hua,Wu, Wen-Hai,Yu, Han-Cheng,Ji, Hong-Bin,Ji, Liang-Nian
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- New TiF4/SiO2 Catalysts for Liquid-phase Epoxidations with Aqueous H2O2
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Ti-supported amorphous silica catalysts are prepared using a simple and original route with TiF4 and are very active in epoxidation reactions with aqueous hydrogen peroxide solutions.
- Jorda, E.,Tuel, A.,Teissier, R.,Kervennal, J.
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- Well-controlled radical-based epoxidation catalyzed by copper complex immobilized on bipyridine-periodic mesoporous organosilica
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The development of synthetic methods and reaction systems for safe radical reactions is of extremely industrial importance. Here we proposed new concept for a safe radical reaction system based on combined use of a mesoporous catalyst and an insoluble solid scavenger. We selected Mukaiyama epoxidation of olefin as a model radical reaction and investigated the catalysis of Cu-bipyridine complexes immobilized on trimethylsilylated bipyridine-periodic mesoporous organosilica as a solid support. The immobilized Cu complex exhibited high catalytic activity and reusability for Mukaiyama epoxidation at low substrate concentration (1 mmol) but free-radical auto-oxidation also occurred at high substrate concentration (7 mmol). Although both epoxidation reactions outside and inside the mesochannels were almost completely quenched by addition of molecular scavenger, addition of solid scavenger allowed quenching the reaction outside the mesopores but not inside the mesopores because the solid scavenger could not access the interior of the mesochannels. Thus, the combined use of a mesoporous catalyst and a solid radical scavenger would offer new reaction system for safe radical reactions.
- Ishikawa, Satoshi,Maegawa, Yoshifumi,Waki, Minoru,Inagaki, Shinji
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- The remarkable catalytic activity of the saturated metal organic framework V-MIL-47 in the cyclohexene oxidation
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The remarkable catalytic activity of the saturated metal organic framework MIL-47 in the epoxidation of cyclohexene is elucidated by means of both experimental results and theoretical calculations. The Royal Society of Chemistry 2010.
- Leus, Karen,Muylaert, Ilke,Vandichel, Matthias,Marin, Guy B.,Waroquier, Michel,Van Speybroeck, Veronique,Van Der Voort, Pascal
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- A mild catalytic oxidation system: FePcOTf/H2O2 applied for cyclohexene dihydroxylation
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Iron (III) phthalocyanine complexes were employed for the first time as a mild and efficient Lewis acid catalyst in the selective oxidation of cyclohexene to cyclohexane-1,2-diol. It was found that the catalyst FePcOTf shown excellent conversion and moderate selectivity relative to other iron (III) phthalocyanine complexes. The optimum conditions of the oxidation reaction catalyzed by FePcOTf/H2O2 have been researched in this paper. Iron (III) phthalocyanine triflate (1 mol %) as catalyst, hydrogen peroxide as oxidant, methanol as solvent, and a mole ratio of substrate and oxidant (H2O2) of 1:1 were used for achieving moderate yields of 1,2-diols under reflux conditions after eight hours.
- Zhou, Baocheng,Chen, Wenxing
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- Enhanced Catalysis Activity in a Coordinatively Unsaturated Cobalt-MOF Generated via Single-Crystal-to-Single-Crystal Dehydration
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Hydrothermal reaction of Co(NO3)2 and terphenyl-3,2″,5″,3′-tetracarboxyate (H4tpta) generated Co3(OH)2 chains based 3D coordination framework Co3(OH)2(tpta)(H2O)4 (1) that suffered from single-crystal-to-single-crystal dehydration by heating at 160 °C and was transformed into dehydrated Co3(OH)2(tpta) (1a). During the dehydration course, the local coordination environment of part of the Co atoms was transformed from saturated octahedron to coordinatively unsaturated tetrahedron. Heterogenous catalytic experiments on allylic oxidation of cyclohexene show that dehydrated 1a has 6 times enhanced catalytic activity than as-synthesized 1 by using tert-butyl hydroperoxide (t-BuOOH) as oxidant. The activation energy for the oxidation of cylcohexene with 1a catalyst was 67.3 kJ/mol, far below the value with 1 catalysts, which clearly suggested that coordinatively unsaturated CoII sites in 1a have played a significant role in decreasing the activation energy. It is interestingly found that heterogeneous catalytic oxidation of cyclohexene in 1a not only gives the higher conversion of 73.6% but also shows very high selectivity toward 2-cyclohexene-1-one (ca. 64.9%), as evidenced in high turnover numbers (ca. 161) based on the open Co(II) sites of 1a catalyst. Further experiments with a radical trap indicate a radical chain mechanism. This work demonstrates that creativity of coordinatively unsaturated metal sites in MOFs could significantly enhance heterogeneous catalytic activity and selectivity. (Graph Presented).
- Ren, Hai-Yun,Yao, Ru-Xin,Zhang, Xian-Ming
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- A model for methane mono-oxygenase: Dioxygen oxidation of alkanes by use of a μ-oxo binuclear iron complex
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Adamantane and cyclohexane are oxidised with dioxygen in CH 2Cl2 in the presence of acetic acid, Zn powder, and a μ-oxo binuclear iron complex.
- Kitajima, Nobumasa,Fukui, Hideno,Moro-Oka, Yoshihiko
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- Photocatalyzed oxidation of cyclohexene and cyclooctene with (nBU4N)4W10O32 and (nBu4N)4W10O32/Fe(III)[meso-tetrakis(2,6- dichlorophenyl)-porphyrin] in homogeneous and heterogeneous systems
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Photoexcitation of (nBu4N)4W10O32 is a suitable mean of oxidizing cyclohexene and cyclooctene with O2 at room temperature and pressure. This process can be carried out in homogeneous solution as well as using the decatungstate in a dispersed form after its heterogenisation on silica. Cyclohexene and cyclooctene are mainly oxidized to the corresponding hydroperoxides as a consequence of primary photoprocesses which lead to the formation of allylic radicals. The presence of the Fe(III)[meso-tetrakis(2,6- dichlorophenyl)porphyrin] chloride as cocatalyst strongly affects the photocatalytic properties of (nBu4N)4W10O32, playing a key role in the allylic-hydroperoxide dependent oxidation of the cycloalkenes. In the photooxidation of cyclohexene, the porphyrin increases the photocatalytic efficiency of the decatungstate in terms of total turnover number and catalyses the decomposition of cyclohexenyl hydroperoxide with the selective formation of cyclohex-2-en1-ol. On the other hand, its presence during the photoinduced oxidation of cyclooctene favours the formation of cyclooctene epoxide by addition of ROO· and RO· radicals to the double bond. In the case of cyclooctene, the heterogenisation of the decatungstate on the solid support also affects the chemoselectivity of the photocatalytic process in the absence of the iron porphyrin complex.
- Molinari,Amadelli,Carassiti,Maldotti
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- Creation, characterisation and performance of vanadyl active sites in microporous and mesoporous silica-based catalysts for the selective oxidation of hydrocarbons
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We here describe how to design vanadium-centred active sites at the inner surfaces of both well defined microporous and well defined mesoporous siliceous hosts. Each type of vanadia-silica catalyst has been extensively characterised (in regard to surface area, pore size and hydrophobicity) and X-ray absorption spectroscopy establishes the active site for these conversions to be a vanadyl group. These centres are catalytically active under mild conditions for both the epoxidation of a typical alkene and the selective oxidation of a typical alkane. Placing methyl groups in the vicinity of this active site significantly enhances the catalytic performance towards epoxidation.
- Oldroyd, Richard D.,Sankar, Gopinathan,Thomas, John Meurig,Hunnius, Matthias,Maier, Wilhelm F.
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- Selective Catalytic Oxidation of Cyclohexene with Molecular Oxygen: Radical Versus Nonradical Pathways
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We study the allylic oxidation of cyclohexene with O2 under mild conditions in the presence of transition-metal catalysts. The catalysts comprise nanometric metal oxide particles supported on porous N-doped carbons (M/N:C, M=V, Cr, Fe, Co, Ni, Cu, Nb, Mo, W). Most of these metal oxides give only moderate conversions, and the majority of the products are over-oxidation products. Co/N:C and Cu/N:C, however, give 70–80 % conversion and 40–50 % selectivity to the ketone product, cyclohexene-2-one. Control experiments in which we used free-radical scavengers show that the oxidation follows the expected free-radical pathway in almost all cases. Surprisingly, the catalytic cycle in the presence of Cu/N:C does not involve free-radical species in solution. Optimisation of this catalyst gives >85 % conversion with >60 % selectivity to the allylic ketone at 70 °C and 10 bar O2. We used SEM, X-ray photoelectron spectroscopy and XRD to show that the active particles have a cupric oxide/cuprous oxide core–shell structure, giving a high turnover frequency of approximately 1500 h?1. We attribute the high performance of this Cu/N:C catalyst to a facile surface reaction between adsorbed cyclohexenyl hydroperoxide molecules and activated oxygen species.
- Denekamp, Ilse M.,Antens, Martijn,Slot, Thierry K.,Rothenberg, Gadi
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- Effect of the synthetic method on the catalytic activity of alumina: Epoxidation of cyclohexene
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Al2O3 was prepared from different inorganic precursors via the Pechini method and compared with Al2O3 prepared by the sol-gel method. Structural characterization of these materials was carried out by FTIR, X-ray diffraction (XRD), N2 adsorption at -196 °C and transmission electron microscopy (TEM). The solids were tested in the epoxidation of cyclohexene and a difference in their catalytic activities was observed. The characterization results indicate that the samples prepared by Pechini have a mixture of γ-alumina and boehmite, a condition favoring catalytic activity, whereas the sol-gel sample is less crystalline due to higher boehmite content. These results indicate that both the nature of the precursor and the method of synthesis strongly affect the catalytic activity of Al2O3.
- Valderruten,Pe?a,Ramírez,Rodríguez-Páez
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- The coordinatively saturated vanadium MIL-47 as a low leaching heterogeneous catalyst in the oxidation of cyclohexene
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A Metal Organic Framework, containing coordinatively saturated V +IV sites linked together by terephthalic linkers (V-MIL-47), is evaluated as a catalyst in the epoxidation of cyclohexene. Different solvents and conditions are tested and compared. If the oxidant TBHP is dissolved in water, a significant leaching of V-species into the solution is observed, and also radical pathways are prominently operative leading to the formation of an adduct between the peroxide and cyclohexene. If, however, the oxidant is dissolved in decane, leaching is negligible and the structural integrity of the V-MIL-47 is maintained during successive runs. The selectivity toward the epoxide is very high in these circumstances. Extensive computational modeling is performed to show that several reaction cycles are possible. EPR and NMR measurements confirm that at least two parallel catalytic cycles are co-existing: one with V+IV sites and one with pre-oxidized V +V sites, and this is in complete agreement with the theoretical predictions.
- Leus, Karen,Vandichel, Matthias,Liu, Ying-Ya,Muylaert, Ilke,Musschoot, Jan,Pyl, Steven,Vrielinck, Henk,Callens, Freddy,Marin, Guy B.,Detavernier, Christophe,Wiper, Paul V.,Khimyak, Yaroslav Z.,Waroquier, Michel,Van Speybroeck, Veronique,Van Der Voort, Pascal
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- Catalytic Behavior of Niobium(v)-Tetraphenylporphyrin in the Oxidation of Cyclohexene with Hydrogen Peroxide Evaluated by 1H NMR Spectroscopy
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The catalytic efficiency of the niobium(v)-tetraphenylporphyrin complex in the oxidation reaction of cyclohexene with aqueous hydrogen peroxide was evaluated using 1H NMR spectroscopy.
- Kaiser, Carlos Roland,Abdel-Rehim, Mona A.,Machado, Mauro Cesar S.,Souza, Eduardo Lauande T.,Lachter, Elizabeth Roditi
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- Efficient Oxygenation of Alkene through Reductive Quenching of Excited Sb(V)tetraphenylporphyrin by Triphenylphosphine
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Novel efficient oxygenation route of cyclohexene into 2-cyclohexen-1-one (Φ=0.14) upon visible light irradiation to tetraphenylporphyrinatoantimony(V) through reductive quenching of the excited triplet porphyrins by triphenylphosphine in aqueous acetonitrile has been found.
- Okamoto, Takanobu,Takagi, Shinsuke,Shiragami, Tsutomu,Inoue, Haruo
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- Catalytic oxidation of hydrocarbons by trinuclear μ-oxo-bridged ruthenium-acetate clusters: Radical versus non-radical mechanisms
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The [Ru3O(H3CCO2)6(py)2 (L)]PF6 clusters, where L = methanol or dimethyl sulfoxide, can be activated by peroxide or oxygen donor species, such as tert-butyl hydroperoxide (TBHP) or iodosylbenzene (PhIO), respectively, generating reactive intermediates of the type [RuIV,IV,III3{double bond, long}O]+. In this way, they catalyse the oxidation of cyclohexane or cyclohexene by TBHP and PhIO, via oxygen atom transfer, rather than by the alternative oxygen radical mechanism characteristic of this type of complexes. In addition to their ability to perform efficient olefin epoxydation catalysis, these clusters also promote the cleavage of the C{single bond}H bond in hydrocarbons, resembling the oxidation catalysis by metal porphyrins.
- Nunes, Genebaldo S.,Alexiou, Anamaria D.P.,Toma, Henrique E.
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- Selective allylic oxidation of cyclohexene by a magnetically recoverable cobalt oxide catalyst
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In this work, we prepared a new magnetically recoverable CoO catalyst through the deposition of the catalytic active metal nanoparticles of 2-3 nm on silica-coated magnetite nanoparticles to facilitate the solid separation from liquid media. The catalyst was fully characterized and presented interesting properties in the oxidation of cyclohexene, as for example, selectivity to the allylic oxidation product. It was also observed that CoO is the most active species when compared to Co2+, Co3O4 and Fe3O4 in the catalytic conditions studied.
- Silva, Fernanda P.,Jacinto, Marcos J.,Landers, Richard,Rossi, Liane M.
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- Tuning of the reaction parameters to optimize allylic oxidation of cyclohexene catalyzed by zeolite-Y entrapped transition metal complexes
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The synthetic protocols for entrapment of transition metal complexes reported here are to expand the diversity in catalysis made possible by the ability of microporous solid to select reactants, transition states, and products based on their molecular size. Herein, we report a synthetic route for the entrapment of transition metal complexes within the nanopores of zeolite-Y. The complexes of transition metals [M = Fe(II), VO(IV)] with Schiff base ligands that are synthesized by simple condensation of 2-hydroxyacetophenone and/or 2-hydroxy-5-chloroacetophenone with ethylenediamine have been entrapped within nanopores of zeolite-Y by flexible ligand method. These materials have been characterized by various physicochemical and spectroscopic techniques such as ICP-OES, FT-IR, 1H and 13C NMR, elemental analyzes, and UV-vis electronic spectral studies, BET, TGA, scanning electron micrographs (SEMs), X-ray diffraction patterns (XRD), conductivity, magnetic susceptibilities as well as AAS. These synthesized catalysts have been utilized as heterogeneous catalysts for liquid phase oxidation of cyclohexene. The reaction parameters have been tuned to optimize higher cyclohexene conversion (%) along with higher selectivity towards the formation of corresponding allylic products. These catalysts were recovered and reused for three times without remarkable loss of activity. Moreover, the intermediate species involved during the catalytic oxidation reaction was synthesized and identified by FTIR and UV-vis spectroscopy.
- Godhani, Dinesh R.,Nakum, Haresh D.,Parmar, Digvijaysinh K.,Mehta, Jignasu P.,Desai, Nisheeth C.
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- Preparation of mesoporous titanosilicate with isolated Ti active centers for cyclohexene oxidation
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We report the preparation of mesoporous titanosilicate with active Ti centres using CTAB as the structure directing agent and ethylenediamine as the complexing agent (TSC-ED). The final material contained isolated Ti4+ centres substituting Si4+ in the mesoporous silica framework. The crucial role played by ethylenediamine in complexing with Ti4+ during the sol-gel process and preventing the phase segregation of TiO2 was studied systematically. The textural parameters, structural order, morphology, nature and co-ordination of Ti species were analyzed using various techniques such as X-ray diffraction (XRD), UV-vis diffused reflectance spectroscopy (UV-vis DRS), UV resonance Raman spectroscopy, Fourier transformed Infra-red spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), transition electron microscopy (TEM), and X-ray photoelectron spectroscopy. Finally, the catalysts were tested for catalytic activity in the oxidation of cyclohexene using various oxidants.
- Gupta,Vinod,Jagadeesan
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- A highly efficient heterogeneous catalyst of cobalt-based coordination polymers for aerobic epoxidation of cyclohexene
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A novel heterogeneous catalyst of cobalt-based coordination polymers has been successfully fabricated using a tyrosine-based derivative. Heterogeneous catalytic experiments on allylic oxidation of cyclohexene indicate that the titled complexes present high catalytic activities using tert-butyl hydroperoxide (t-BuOOH) as an oxidant. The activation energy for the whole process of oxidation of cyclohexene has been calculated to be 25.5 kJ mol-1, which indicates the important role of the selected ancillary ligands in the synthesis of the heterogeneous catalyst.
- Yu, Fan
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- Porous and hollow metal-layer@SiO2 nanocomposites as stable nanoreactors for hydrocarbon selective oxidation
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Porous and hollow metal-layer@SiO2 nanocomposites (metal = Au, Ag, Cu) have high catalytic activity and stability for cyclohexene selective oxidation.
- Zhang, Hengchao,Huang, Hui,Liu, Yang,Han, Xiao,Ma, Zheng,Zhang, Lili,Li, Haitao,Kang, Zhenhui
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- Ultrafast synthesis of nanosized Ti-Beta as an efficient oxidation catalyst: Via a structural reconstruction method
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As a representative selective oxidation titanosilicate catalyst, a Ti-Beta zeolite is less used in comparison with TS-1, Ti-MWW and Ti-MOR, mostly due to its high hydrophilicity originating from a BEA? intergrowth framework. A novel recrystallization method was proposed in the present study to prepare highly hydrophobic Ti-Beta with nanosized crystals (90 nm), high Ti content (Si/Ti = 20) and intercrystal mesoporosity. The fluoride-assisted recrystallization was realized quickly by dissolving extensively a dealuminated Beta zeolite in a mixture of a tetraethylammonium aqueous solution and Ti precursor, producing highly crystalline Ti-Beta in an extremely short time of 1 h. The obtained Ti-Beta zeolite exhibited superior catalytic activity in the liquid-phase epoxidation reactions of bulky alkenes like cyclohexene with hydrogen peroxide or tert-butyl hydroperoxide as an oxidant, compared to those Ti-Beta catalysts prepared by conventional hydrothermal or secondary synthesis routes.
- Wang, Bowen,Xu, Hao,Zhu, Zhiguo,Guan, Yejun,Wu, Peng
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- Characteristics of cationic phase-transfer catalysts in the oxidation of hydrocarbons by O2
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The oxidation of tetralin and cyclohexene by O2 was investigated in the presence of cationic phase-transfer catalysts (PTCs). It was found that the oxidation takes place analogously to the recently investigated catalysed decompositions of hydroperoxide initiator molecules. The natures of both the onium cation and the counteranion are determining factors. The catalytic activity of the onium salt is determined by the effective charge on the onium ion and by the size and polarizability of the anion. For both hydrocarbons, the primary product of oxidation is the corresponding hydroperoxide, which may undergo further oxidation. For tetralin, tetralyl hydroperoxide underwent disproportionation into O2 and tetralol, and reuse of the O2 thus produced resulted in a considerable "overoxidation" in the closed reactor. Tetralone was formed in a smaller amount. The main products in the oxidation of cyclohexene were its hydroperoxide, cyclohexene oxide and 2-cyclohexen-1-ol. In contrast to the oxidation of tetralin, "overoxidation" did not occur here, and the formation of 2-cyclohexen-1-one was never observed. The oxidations of these hydrocarbons in the presence of cationic PTCs proved to be strongly influenced by the concentration of homogeneously dissolved water. The oxidation products of these hydrocarbons also exerted considerable influence on the progress of the oxidation.
- Csanyi,Jaky
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- A Bimetallic Pure Inorganic Framework for Highly Efficient and Selective Photocatalytic Oxidation of Cyclohexene to 2-Cyclohexen-1-ol
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Abstract: The highly efficient and selective photocatalytic oxidation of cyclohexene with molecular oxygen under mild conditions is an important objective in chemical synthesis. In this work, a pure inorganic framework CoMo was self-assembly prepared under solvothermal conditions by incorporating simple MoO42?, cobalt (II) ion. The catalyst CoMo was well characterized by infrared spectroscopy (FTIR), nitrogen adsorption–desorption, powder X-ray diffraction (XRD), scanning electron spectroscopy (SEM), and X-ray photoelectron spectroscopy (XPS) methods. It displayed high efficiency and selectivity in the photocatalytic oxidation of cyclohexene to 2-cyclohexen-1-ol in O2 atmosphere. The influence of solvents, oxidants, pressure of oxygen, reaction temperature, light source and time on the reaction was investigated. More interestingly, the selectivity of the reaction in 4-ethyltoluene was much higher than that in other solvents. Graphic Abstract: [Figure not available: see fulltext.].
- Shi, Xiaoyun,Shi, Zhuolin,Niu, Guiqin,Si, Chen,Han, Qiuxia,Zhang, Jingjing
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- Magnetically recoverable copper oxide catalysts for aerobic allylic oxidation of cyclohexene
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Magnetically recoverable copper oxide catalysts prepared by sol-immobilization method exhibited interesting properties for the allylic oxidation of cyclohexene with molecular oxygen as the sole oxidant. The catalysts were prepared by immobilization of pre-synthesized PVA (polyvinyl alcohol)-stabilized Cu2O nanoparticles (NPs) on a magnetically recoverable support; the catalyst was further oxidized to CuO NPs after calcination at 600?°C. Both catalysts can selectively oxidize cyclohexene through allylic oxidation to give 2-cyclohexene-1-one as the main product, but CuO was identified as the most active species providing 90% cyclohexene conversion and 96% selectivity for allylic products under 100?°C and 4?bar pressure of O2 for 6?h of reaction time. The catalysts were magnetically recovered without metal leaching and could be reused in at least six consecutive runs.
- da Silva, Fernanda Parra,Gon?alves, Renato V.,Rossi, Liane M.
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- AlPO4 MOLECULAR SIEVES MODIFIED WITH METAL CHELATE COMPLEXES
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A new method for modification AlPO4 molecular sieves has been presented.Lack of ion-exchange properties makes the modification of aluminium phosphates for catalytic applications difficult.We have developed a method that involves the crystallization of AlP
- Kowalak, Stanislaw,Balkus, Kenneth J.
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- Oxidation of cyclohexene with t-butyl hydroperoxide catalyzed by transition metal oxide clusters
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Organometallic oxide clusters (cp' = η5-C5Me5) and 2 catalyze the oxidation of cyclohexene with t-butyl hydroperoxide to give allylic oxidation products mainly and epoxycyclohexane selectively, respectively.
- Zhang, Cuiju,Ozawa, Yoshiki,Hayashi, Yoshihito,Isobe, Kiyoshi
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- Photocatalytic Oxygenation of Strained Alicyclic Alkenes with μ-Oxo-bis and Molecular Oxygen
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Iron(III) porphyrins are active catalysts for the photocatalytic epoxidation of strained cyclic alkenes and their methyl substituted derivatives with molecular oxygen.
- Weber, Lutz,Haufe, Guenter,Rehorek, Detlef,Hennig, Horst
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- Efficient allylic oxidation of cyclohexene catalyzed by trimetallic hybrid nano-mixed oxide (Ru/Co/Ce)
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The paper deals with the reactivity of RuO2/Co3O 4/CeO2 nanoparticles prepared by a reverse micelle approach, which was precipitated by alkali-hydrolysis of RuCl3, Co(NO3)2 and Ce(NO3)2 and transformed into RuO2/Co3O4/CeO2 catalyst by calcinations in air at 400 °C. The catalysts were investigated with XRD, TEM, XPS, and BET techniques and were tested for oxidation of cyclohexene. The nano-catalyst exhibited high catalytic activities for the oxidation of cyclohexene to the corresponding α,β-unsaturated ketone under heterogeneous condition. In order to obtain maximum conversion of cyclohexene, the reaction parameters, like reaction temperature and time, were optimized. Under the optimized conditions, a maximum of 97.7% cyclohexene conversion and 95% selectivity, was achieved with RuO2/Co 3O4/CeO2 mixed oxide nano-catalyst.
- Ghiaci, Mehran,Aghabarari, Behzad,Botelho Do Rego,Ferraria,Habibollahi, Saeed
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- Hierarchical zeolites and their catalytic performance in selective oxidative processes
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Hierarchical ZSM-5 zeolites prepared using a simple alkali treatment and subsequent HCl washing are found to exhibit unprecedented catalytic activities in selective oxidation of benzyl alcohol under microwave irradiation. The metal-free zeolites promote the microwave-assisted oxidation of benzyl alcohol with hydrogen peroxide in yields ranging from 45-35 % after 5 min of reaction under mild reaction conditions as well as the epoxidation of cyclohexene to valuable products (40-60 % conversion). The hierarchically porous systems also exhibited an interesting catalytic activity in the dehydration of N,N-dimethylformamide (25-30 % conversion), representing the first example of transition-metal free catalysts in this reaction.
- Ojeda, Manuel,Grau-Atienza, Aida,Campos, Rafael,Romero, Antonio A.,Serrano, Elena,Maria Marinas, Jose,García Martínez, Javier,Luque, Rafael
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- Selective Oxidation of Cyclohexene with H2O2 Catalyzed by Resin Supported Peroxo Phosphotungstic Acid Under Mild Conditions
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Abstract: A series of modified chloromethyl polystyrene resins loaded with peroxo phosphotungstic acid catalysts were synthesized for the selective oxidation of cyclohexene. The surface of resin was enriched with high concentration quaternary ammonium salt, and grafted with a large amount of peroxo PW-anion through ion exchange. The novel resin catalyst showed excellent cyclohexene conversion and epoxide selectivity using 30% H2O2 as oxidant at ambient temperature. Furthermore, the resin catalyst exhibited excellent recycling stability, which can be reused by a simple filtration and the peroxo phosphotungstic acid did not leach into the solvent after reaction. Graphic Abstract: [Figure not available: see fulltext.]
- Liu, Jia,Yang, Guoqiang,Liu, Ying,Zhou, Zheng,Zhang, Zhibing,Hu, Xingbang
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- Strategies to improve the epoxidation activity and selectivity of Ti-MCM-41
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Two strategies to improve the catalytic activity of Ti-MCM-41 materials in the epoxidation of olefins are described; the first approach involves silylation of the surface of Ti-MCM-41 which produces a very hydrophobic catalyst whereas the second approach is based on removal of water from the reaction media; the increase in activity is not due to a change in the intrinsic activity of the Ti sites, but rather to a decrease of the catalyst deactivation by reducing the formation of diols produced by ring opening of the epoxide.
- Corma, Avelino,Domine, Marcelo,Gaona, Jose A.,Jorda, Jose L.,Navarro, Maria T.,Rey, Fernando,Perez-Pariente, Joaquin,Tsuji, Junpei,McCulloch, Beth,Nemeth, Laszlo T.
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- Selective allylic oxidation of cyclohexene catalyzed by nitrogen-doped carbon nanotubes
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Carbon nanotubes (CNTs) and nitrogen-doped CNTs (NCNTs) were systematically investigated as metal-free catalysts in the selective allylic oxidation of cyclohexene using molecular oxygen as oxidant in the liquid phase. High cyclohexene conversion (up to 59.0%) and 620.1 mmol g-1 h -1 mass-normalized activity were obtained for NCNTs, competing with the state-of-the-art metal catalysts. The positive effect of nitrogen dopant on the performance of CNTs was demonstrated, with respect to the aspects of enhancing activity and increasing selectivity of 2-cyclohexen-1-one, allowing for a ketone/alcohol ratio of 3.7 at 59% conversion. The unique catalytic role of NCNTs was attributed to their capability to promote the radical chain propagation via stabilizing peroxyl and cycloxyl radicals, which boosted the further conversion of 2-cyclohexen-1-ol toward 2-cyclohexen-1-one as well.
- Cao, Yonghai,Yu, Hao,Peng, Feng,Wang, Hongjuan
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- A Pronounced Catalytic Activity of PW11CoO395- for Epoxidation of Alkenes by Molecular Oxygen in the Presence of Aldehyde
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The epoxidation of cyclohexene, 1-decene, and styrene by molecular oxygen in the presence of aldehydes such as isobutyraldehyde and pivalaldehyde was efficiently catalyzed at 303 K by mono-cobalt-substituted Keggin-type heteropolytungstate.
- Mizuno, Noritaka,Hirose, To-oru,Tateishi, Masaki,Iwamoto, Masakazu
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- Heteropolytungstate nanoparticles: Microemulsion-mediated preparation and investigation of their catalytic activity in the epoxidation of olefins
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Keggin type Q3PW12O40 nanoparticles (Q = cetyltrimethylammonium cation) were synthesized in water-in-oil (w/o) microemulsion consisted of water/cetyltrimethylammonium bromide/n-butanol/isooctane. Reaction of Na2WO4, Na2HPO4 and hydrochloric acid within water containing nanoreactors of reverse micelles resulted in the preparation of Q3PW12O40 nanoparticles. The resultant nanoparticles were analyzed by physicochemical methods such as FT-IR spectroscopy, X-ray diffraction, energy-dispersive X-ray analysis, thermogravimetric analyses (TGA-DTA), scanning and transmission electron microscopy and atomic force microscopy which show nearly uniform spherical nanoparticles with size of about 15 nm. Finally, catalytic activity of the Q3PW12O40 nanoparticles was examined in the epoxidation of olefins with H2O2. The prepared nanoparticles acted as recoverable and reusable catalyst in the epoxidation of olefins with H2O2.
- Masteri-Farahani,Ghorbani
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- Protons Make Possible Heterolytic Activation of Hydrogen Peroxide over Zr-Based Metal-Organic Frameworks
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The catalytic performance of zirconium-based metal-organic frameworks (UiO-66, UiO-67, and MOF-801) in cyclohexene oxidation with aqueous hydrogen peroxide can be greatly improved by adding a source of protons directly into the reaction mixture. A blend of Zr-MOF and protons favors heterolytic activation of H2O2 and makes possible selective formation of epoxide and diol with negligible formation of allylic oxidation products. Additives of HClO4 suppress the rates of H2O2 decomposition over Zr-MOF and increase oxidant utilization efficiency. No structural changes occur in the acid-activated Zr-MOF. The catalyst does not suffer metal leaching, reveals a truly heterogeneous nature of the catalysis, and can be recovered and reused.
- Maksimchuk, Nataliya V.,Lee, Ji Sun,Solovyeva, Marina V.,Cho, Kyung Ho,Shmakov, Aleksandr N.,Chesalov, Yuriy A.,Chang, Jong-San,Kholdeeva, Oxana A.
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- (μ-O,O′)-nitrito bridged 3-D coordination frameworks of M2+ (Mn Co, Zn) with mab and jsm topology
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Four new nitrito-bridged coordination polymers of formulation [Zn(NO2)2(H2O)2]n (1) and [M(bipy)(NO2)2]n [M = Zn (2), Co (3), Mn (4)] were synthesized under solvothermal condition using N,N-dimethylformamide (DMF) as a reducing solvent. Theoretical calculation suggests in situ reduction of nitrate to nitrite with high spontaneity and without any thermodynamic barrier (ΔG = ?20.4?kcal/mol). All the complexes were characterized by elemental analysis, FT-IR spectroscopy, UV–vis spectroscopy, Raman Spectroscopy, TG analysis as well as by single crystal X-ray diffraction methods. TD-DFT approach has been employed to assign the electronic transitions occurring in the cobalt(II) complex (3) and were compared with those observed experimentally. This work also describes the preliminary studies on heterogeneous oxidation of cyclohexene by 2&3 in acetonitrile medium using TBHP.
- Paul, Rima,Guha, Ankur K.,Saikia, Lakshi,Bora, Sanchay J.
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- Surface-mediated reactions. 7. Unsupported reagents
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(equation presented) Some solid reagents traditionally supported on silica gel or alumina are also effective as heterogeneous reactants in the absence of a support. Moist magnesium monoperoxyphthalate (MMPP), either suspended in CH2Cl2 or solventless, is a convenient alternative to peroxycarboxylic acids for oxidation of sulfides and epoxidation of alkenes. The latter reaction exhibits an unusual order of reactivity: trisubstituted > disubstituted > tetrasubstituted. Unsupported moist Ca(OCl)2 and OXONE are also effective oxidants.
- Foti, Christopher J.,Fields, John D.,Kropp, Paul J.
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- Increased selectivity for allylic oxidation of cyclohexene using TiO2 modified V2O5/MoO3 catalysts
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V2O5 and MoO3 mixed oxides supported by SiO2 were studied as the catalysts in the aqueous phase allylic oxidation of cyclohexene to unsaturated alcohol 2-cyclohexene-1-ol and unsaturated ketone 2-cyclohexene-1-one. The additional layer of TiO2 deposited by atomic layer deposition significantly suppresses the epoxidation pathway and the formation of cyclohexane oxide and cyclohexane-1, 2-diol. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) were used to study the relationship between the structure of the catalysts and their catalytic performance. The effects on the catalytic activity of different solvent, hydrogen peroxide to cyclohexene ratio, and reusability were investigated.
- Yang, Guoqiang,Huff, Matthew D.,Du, Huiyuan,Zhang, Zhibing,Lei, Yu
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- Magnetic properties and catalytic performance of iron-containing mesoporous molecular sieves
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Fe-containing mesoporous molecular sieves were synthesized by the wet impregnation method with two different metallic loadings. The resulting iron oxide/silica composites were then submitted to a reduction treatment for 6 h at 873 K, under H2 flow. The microstructure of both, the Si-MCM-41 host and the impregnated composites were characterized by XRD, N2 adsorption, DRUV-vis and M?ssbauer spectroscopy. The magnetic behavior of each microstructure was characterized by the magnetization dependence on the magnetic field (up to 1.5 T) and temperature (between 5 and 300 K). The catalytic performance was tested for cyclohexene oxidation by hydrogen peroxide and further correlated with the observed magnetic properties. It was found that the reduction treatment largely affects the selectivity to reaction products, leading to catalysts exhibiting a selectivity of 80% towards the allylic oxidation products. This is attributed to a large free radical generation arising from the interaction between the hydrogen peroxide and the partially reduced iron species (mainly Fe0 and Fe3O4), exhibiting superparamagnetic and/or ferromagnetic character.
- Elías, Verónica R.,Oliva, Marcos I.,Urreta, Silvia E.,Silvetti, Silvia P.,Sapag, Karim,Mudarra Navarro, Azucena M.,Casuscelli, Sandra G.,Eimer, Griselda A.
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- Catalytic oxidation of cyclohexene by molecular oxygen over isopolyoxometalates
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Isopolyoxomolybdates exhibited high selectivities for the industrially useful products (cyclohexene oxide and 2-cyclohexen-1-ol) catalyzing effectively the reaction of initial product cyclohexenyl hydroperoxide with cyclohexene in the oxidation of cyclohexene by molecular oxygen.
- Liu, Yanyong,Murata, Kazuhisa,Inaba, Megumu,Nakajima, Hitoshi,Koya, Masahiko,Tomokuni, Keizou
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- Engineering an atomically well defined active site for the catalytic epoxidation of alkenes
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The improvement effected by replacing one of the three O-Si≡ groups to which a TiIV ion is anchored (to a mesoporous silica support) by a O-Ge≡ group is described, as is the detailed structure retrieved by in situ X-ray absorption spectroscopy of the created active site.
- Oldroyd, Richard D.,Thomas, John Meurig,Sankar, Gopinathan
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- Kinetic Studies on the Oxoiron(IV) Complex with Tetradentate Aminopyridine Ligand PDP: Restoration of Catalytic Activity by Reduction with H2O2
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Oxoiron(IV) is a common catalytic byproduct observed in the oxidation of alkenes by the combination of H2O2 and nonheme iron catalysts including complex 1, FeIIPDP? (where PDP? = bis(3,5-dimethyl-4-methoxypyridyl-2-methyl)-(R,R)-2,2′-bipyrrolidine). The oxoiron(IV) species have been proposed to arise by O-O homolysis of the peroxyiron(III) or acylperoxyiron(III) intermediates formed during the presumed FeIII-FeV catalytic cycle and have generally been regarded as off-pathway. We generated complex 1IV=O (λmax = 730 nm, ? = 350 M-1 cm-1) directly from 1 and an oxygen atom donor IBXi-Pr (isopropyl 2-iodoxybenzoate) in acetonitrile in the temperature range from-35 to +25 °C under stopped-flow conditions. Species 1IV=O is metastable (half-life of 2.0 min at +25 °C), and its decay is accelerated in the presence of organic substrates such as thioanisole, alkenes, benzene, and cyclohexane. The reaction with cyclohexane-d12 is significantly slower (KIE = 4.9 ± 0.4), suggesting that a hydrogen atom transfer to 1IV=O is the rate limiting step. With benzene-d6, no significant isotope effect is observed (KIE = 1.0 ± 0.2), but UV-vis spectra show the concomitant formation of an intense 580 nm band likely due to the Fe(III)-phenolate chromophore, suggesting an electrophilic attack of 1IV=O on the aromatic system of benzene. Treatment of 1IV=O with H2O2 resulted in rapid decay of its 730 nm visible band (k = 102.6 ± 4.6 M-1 s-1 at-20 °C), most likely occurring by a hydrogen atom transfer from H2O2. In the presence of excess H2O2, the oxoiron(IV) is transformed into peroxyiron(III), as seen from the formation of a characteristic 550 nm visible band and geff = 2.22, 2.16, and 1.96 electron paramagnetic resonance (EPR) spectroscopy signals. Reductively formed 1III-OOH was able to re-enter the catalytic cycle of alkene epoxidation by H2O2, albeit with lower yields versus those of oxidatively formed (i.e., 1 + H2O2) peroxyiron(III) owing to a loss of ca. 40% active iron. As such, the oxoiron(IV) species can be reintroduced to the catalytic cycle with extra H2O2, acting as an iron reservoir. Alternatively, peroxycarboxylic acids, which have a stronger O-H bond dissociation energy, do not reduce 1IV=O, ensuring that more oxidant is productively employed in substrate oxidation. While this reaction with H2O2 may occur for other nonheme oxoiron(IV) complexes, the only previously reported examples are 3IV=O and 4IV=O, which are reduced by hydrogen peroxide 130- A nd 2900-fold more slowy, respectively (as in Angew. Chemie-Int. Ed. 2012, 51 (22), 5376-5380, DOI: 10.1002/anie.201200901).
- Piquette, Marc C.,Kryatov, Sergiy V.,Rybak-Akimova, Elena V.
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- Oxygen Atom Transfer Mechanism for Vanadium-Oxo Porphyrin Complexes Mediated Aerobic Olefin Epoxidation
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The development of catalytic aerobic epoxidation by numerous metal complexes in the presence of aldehyde as a sacrificial reductant (Mukaiyama epoxidation) has been reported, however, comprehensive examination of oxygen atom transfer mechanism involving free radical and highly reactive intermediates has yet to be presented. Herein, meso-tetrakis(pentafluorophenyl) porphyrinatooxidovanadium(IV) (VOTPFPP) was prepared and proved to be efficient toward aerobic olefin epoxidation in the presence of isobutyraldehyde. In situ electron paramagnetic resonance spectroscopy (in situ EPR) showed the generation, transfer pathways and ascription of free radicals in the epoxidation. According to the spectral and computational studies, the side-on vanadium-peroxo complexes are considered as the active intermediate species in the reaction process. In the cyclohexene epoxidation catalyzed by VOTPFPP, the kinetic isotope effect value of 1.0 was obtained, indicating that epoxidation occurred via oxygen atom transfer mechanism. The mechanism was further elucidated using isotopically labeled dioxygen experiments and density functional theory (DFT) calculations.
- Han, Qi,Huang, Jia-Ying,Ji, Hong-Bing,Liu, Xiao-Hui,Tao, Lei-Ming,Xue, Can,Yu, Hai-Yang,Zhou, Xian-Tai,Zou, Wen
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p. 115 - 122
(2021/12/04)
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- Dioxo-molybdenum(VI) unsymmetrical Schiff base complex supported on CoFe2O4@SiO2 nanoparticles as a new magnetically recoverable nanocatalyst for selective epoxidation of alkenes
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In the present work, a dioxo-molybdenum unsymmetrical Schiff base complex, [MoO2(salenac-OH)], in which salenac-OH = [9-(2',4'-dihydroxyphenyl)-5,8-diaza-4-methylnona-2,4,8-trienato](-2), has been prepared and covalently immobilized on the sili
- Ardakani, Mehdi Hatefi,Sabet, Mohammad,Samani, Mahnaz
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- Polyamine-functionalized imidazolyl poly(ionic liquid)s for the efficient conversion of CO2 into cyclic carbonates
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Global warming is becoming a challenging issue due to the emission of a large number of greenhouse gases, mainly CO2. The transformation of CO2 into chemicals with high additional value is considered a promising and sustainable way to solve the “greenhouse effect”. Herein, a series of polyamine-functionalized imidazolyl poly(ionic liquid)s (PILs) modified by triethylenetetramine (TETA) were synthesized as heterogeneous catalysts to convert CO2 into cyclic carbonates. The synergistic effect of nucleophile (bromide anions) and polyamine groups in promoting CO2 conversion was explored by density functional theory (DFT) calculations, which is critical to improve the catalytic performance. When the anions of ionic liquids acted as nucleophiles to attack the epoxide from the C–O bond with less steric hindrance, the substrate epoxide and CO2 can be activated by hydrogen bonding with amine group protons. Therefore, PILs modified by TETA (N4-PIL-x) have been verified to possess high efficiency and stable reusability for the cycloaddition of epoxides with CO2 without solvent, metal, and co-catalyst, of which N4-PIL-2 can achieve 98.0% conversion of epichlorohydrin (ECH) with a turnover frequency (TOF) value as high as 42.4 h?1 under ambient pressure; moreover, the complete conversion of epichlorohydrin is obtained in only 4 h at 1.0 MPa CO2 pressure.
- Cheng, Guoe,Ge, Yuansheng,Ke, Hanzhong,Li, Xiaoguang,Liu, Wei,Zhang, Qiang,Zou, Yizhen
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p. 273 - 281
(2022/01/19)
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- Catalytic Performance of Zr-Based Metal–Organic Frameworks Zr-abtc and MIP-200 in Selective Oxidations with H2O2
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The catalytic performance of Zr-abtc and MIP-200 metal–organic frameworks consisting of 8-connected Zr6 clusters and tetratopic linkers was investigated in H2O2-based selective oxidations and compared with that of 12-coordinated UiO-66 and UiO-67. Zr-abtc demonstrated advantages in both substrate conversion and product selectivity for epoxidation of electron-deficient C=C bonds in α,β-unsaturated ketones. The significant predominance of 1,2-epoxide in carvone epoxidation, coupled with high sulfone selectivity in thioether oxidation, points to a nucleophilic oxidation mechanism over Zr-abtc. The superior catalytic performance in the epoxidation of unsaturated ketones correlates with a larger amount of weak basic sites in Zr-abtc. Electrophilic activation of H2O2 can also be realized, as evidenced by the high activity of Zr-abtc in epoxidation of the electron-rich C=C bond in caryophyllene. XRD and FTIR studies confirmed the retention of the Zr-abtc structure after the catalysis. The low activity of MIP-200 in H2O2-based oxidations is most likely related to its specific hydrophilicity, which disfavors adsorption of organic substrates and H2O2.
- Maksimchuk, Nataliya V.,Ivanchikova, Irina D.,Cho, Kyung Ho,Zalomaeva, Olga V.,Evtushok, Vasiliy Yu.,Larionov, Kirill P.,Glazneva, Tatiana S.,Chang, Jong-San,Kholdeeva, Oxana A.
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supporting information
p. 6985 - 6992
(2021/03/17)
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- Direct hydrothermal synthesis of Mo-containing MFI zeolites using Mo-EDTA complex and their catalytic application in cyclohexene epoxidation
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A series of Mo-containing MFI zeolites with different Mo loadings (Mo-MFI-n, n represent the initial Si/Mo molar ratio) was hydrothermally synthesized by using tetrapropylammonium hydroxide as the template and Mo-EDTA complex as the Mo source. Various characterization results demonstrated that the use of the Mo-EDTA complex is beneficial for the incorporation of more Mo species into the MFI-type zeolites. The special complexing capability of EDTA2– plays a critical role in adjusting the release rate of the Mo species to combine with the Si tetrahedron species during the zeolite growth process, thus leading to a uniform distribution of Mo in the MFI framework. In addition, a small portion of extra-framework Mo clusters may be distributed inside the channels or near the pore window of the zeolites. The catalytic properties of these Mo-containing MFI zeolites were evaluated for the epoxidation of cyclohexene with H2O2 as the oxidant. The composition-optimized catalyst, Mo-MFI-50, efficiently converted cyclohexene to the corresponding epoxide with a relatively high conversion (93%) and epoxide selectivity (82%) at 75 °C after 9 h of reaction. Moreover, the resultant Mo-containing MFI catalyst exhibited excellent structural stability and recoverability and was easily recycled by simple filtration without the need for calcination treatment.
- Chang, Xinyu,Jia, Mingjun,Miao, Songsong,Sun, Yuting,Xu, Lifen,Zhang, Haoyang
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p. 2265 - 2274
(2021/09/20)
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- Organocatalytic epoxidation and allylic oxidation of alkenes by molecular oxygen
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Pyrrole-proline diketopiperazine (DKP) acts as an efficient mediator for the reduction of dioxygen by Hantzsch ester under mild conditions to allow the aerobic metal-free epoxidation of electron-rich alkenes. Mechanistic crossovers are underlined, explaining the dual role of Hantzsch ester as a reductant/promoter of the DKP catalyst and a simultaneous competitor for the epoxidation of alkenes when HFIP is used as a solvent. Expansion of this protocol to the synthesis of allylic alcohols was achieved by adding a catalytic amount of selenium dioxide as an additive, revealing a superior method to the classical application of t-BuOOH as a selenium dioxide oxidant.
- Orfanidou, Maria,Petsi, Marina,Zografos, Alexandros L.
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supporting information
p. 9172 - 9178
(2021/11/30)
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- Lanthanide metal-organic frameworks for catalytic oxidation of olefins
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Two isostructural lanthanide metal-organic frameworks (Ln-MOF-589, Ln = La3+, Ce3+), constructed from a tetratopic linker, benzoimidephenanthroline tetracarboxylic acid (H4BIPA-TC), have been solvothermally synthesized and characterized. These Ln-MOF-589 materials consist of Lewis acid [Ln2(-COO)6(-COOH)2(H2O)6] units and a naphthalene diimide core, which exhibited promising catalytic activity for the oxidation of olefins. Among them, Ce-MOF-589 exhibited outstanding performance with high conversions of styrene and cyclohexene (94 and 90%, respectively), and good selectivities towards styrene oxide and 2-cyclohexen-1-one (85, and 95%, respectively). Notably, the catalytic activity of Ce-MOF-589 outperformed that of homogeneous and heterogeneous catalysts, and representative MOFs. Also, Ce-MOF-589 can be recycled for at least up to six cycles with no significant loss of catalytic performance.
- Tran,Nguyen, Phuong T. K.
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p. 2090 - 2102
(2021/02/06)
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- Instant Cyclohexene Epoxidation Over Ni-TUD-1 Under Ambient Conditions
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Abstract: To avoid the aggregation problem and activity loss of nickel oxide (NiO) nanoparticles (NPs) in organic reactions, NiO NPs were incorporated into TUD-1 mesoporous material. One-step sol–gel preparation was applied to prepare four samples of Ni incorporated in TUD-1 silica matrix with different Ni content. The four samples with Si/Ni ratio = 100, 50, 20, and 10 were characterized by means of elemental analysis, powder X-ray diffraction (XRD), Raman spectroscopy, N2 sorption measurements, scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), and high-resolution transmission electron microscopy (HR-TEM). The characterization analysis showed that Ni2+ ions were incorporated into the silica matrix as individual isolated active sites at Ni content smaller than 2 wt%, and as nanoparticles of NiO when the loading is equal to or higher than 5 wt%. The size of NiO NPs inside the silica matrix is highly dependent on the Ni content, i.e. the size of NiO NPs when the loading was 5 wt% and 10 wt% was 5–10 and 40–60?nm, respectively. The catalytic activity of Ni-TUD-1 was investigated in the epoxidation reaction of cyclohexene at room temperature by using meta-chloroperoxybenzoic acid (m-CPBA) as an oxidant. The obtained results showed that Ni-TUD-1 exhibited superior activity in which 100% conversion of cyclohexene with > 90% selectivity towards cyclohexene oxide was obtained instantly. This result was found to benchmark not only the unsupported NiO nanoparticles, but also the reported catalysts at similar conditions. Graphic Abstract: [Figure not available: see fulltext.].
- Hamdy, Mohamed S.,Al-Zaqri, Nabil,Sahlabji, Taher,Eissa, Murad,Haija, Mohammad Abu,Alhanash, Abdullah M.,Alsalme, Ali,Alharthi, Fahad A.,Abboud, Mohamed
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p. 1612 - 1622
(2020/10/14)
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- Selective cyclohexene oxidation to allylic compounds over a Cu-triazole frameworkviahomolytic activation of hydrogen peroxide
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Utilization of metal-organic frameworks as heterogeneous catalysts is crucial owing to their abundant catalytic sites and well-defined porous structures. Highly robust [Cu3(trz)3(μ3-OH)(OH)2(H2O)4]·2H2O (trz = 1,2,4-triazole) was employed as a catalyst for liquid-phase cyclohexene oxidation with hydrogen peroxide (H2O2). Possessing the porous structure together with Lewis acid attributes from the triangular [Cu3(trz)3(μ3-OH)] center, selective oxidation of cyclohexene to allylic products gives a molar yield of 31% with 87% selectivity. According to the highly selective allylic production, the reaction over the present Cu-MOF plausibly occursviahomolytic activation of H2O2. This finding elucidates the unique features of the MOF for efficient catalysis of cyclohexene oxidation.
- Adpakpang, Kanyaporn,Bureekaew, Sareeya,Ponchai, Panyapat
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supporting information
p. 7917 - 7921
(2021/06/18)
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- Trans(Cl)-2,2′-bipyridinedicarbonyldichlororuthenium(II) complex catalyzed oxidation of olefins, aryl hydrocarbons and alcohols in homogeneous phase
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Catalytic oxidation of organic substrates has wide applications in chemical industries due to which huge extensive research work is continuously going on throughout the world. Present study reports efficacious use of Trans (Cl)-2,2′-bipyridinedicarbonyldichlororuthenium(II) complex catalyzed oxidation of internal and terminal olefins, aryl hydrocarbons and alcohols. CH2Cl2–C2H5OH (6:4) was suitable solvent system for these oxidation reactions. The normal pressure oxidation reaction has been carried out at 1 ?atm. Pressure of oxygen and at 300C. The high pressure oxidation reaction was done at 4.48 ?× ?103 KNm3 pressure of oxygen and at 600C. No diminished catalytic activity was observed while checking the recyclability of catalyst up to 6–8 catalytic runs. Catalytic activity was also investigated using tert-butyl hydroperoxide as oxidant inspite of di-oxygen. Effect of different parameters on the rate of oxidation was also studied i.e. extra ligand, temperature, solvents, acids and bases. Kinetic studies have been done and on the basis of kinetics, the mechanism is proposed.
- Sharma, Varsha,Pant, Bhawana,Prakash, Deep,Sagar, Priyanka
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- Structural investigation of the catalytic activity of Fe(III) and Mn(III) Schiff base complexes
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Two novel manganese (III) and iron (III) complexes of an N,N-bis(1-naphthalidimine)-o phenylene diamine ligand have been successfully synthesized and characterized by various analytical techniques including single crystal X-ray structure analysis. The lig
- Bendia, Sabrina,Bourzami, Riadh,Weiss, Jean,Ouari, Kamel
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- Mn(III)-Porphyrin Immobilized on the Graphene Oxide-Magnetite Nanocomposite as an Efficient Heterogeneous Catalyst for the Epoxidation of Alkenes
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In this research, β-tetra-brominated meso-tetraphenylporphyrinatomanganese(III) acetate [MnTPPBr4(OAc)] (MnPor) was anchored onto a magnetite imidazole-modified graphene oxide nanosheet (Fe3O4.GO.Im). The obtained catalyst (Fe3O4.GO.Im@MnPor) was characterized through Fourier transform infrared (FT-IR) and diffuse reflectance UV–Visible spectrophotometry (DR UV–Vis), powder X-ray diffractometry (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) spectroscopy, thermogravimetric analysis (TGA) and atomic absorption spectroscopy. The characterization was performed to determine the amount of manganese porphyrin loaded on the GO support. The new immobilized catalyst was employed for the efficient epoxidation of different alkenes with urea hydrogen peroxide (UHP) and acetic acid (HOAc) as oxidant activators under mild conditions. Olefins were oxidized efficiently to their corresponding epoxide with 63–100% selectivity in the presence of Fe3O4.GO.Im@MnPor. Moreover, an remarkable turnover frequency (93) was achieved for the oxidation of α-pinene. The graphene oxide-bound Mn-porphyrin was recovered from the reaction mixture by magnetic decantation and reused several times. Graphic Abstract: [Figure not available: see fulltext.]
- Bahrami, Elnaz,Hajian, Robabeh
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- Investigation of physicochemical properties for novel perrhenate ionic liquid and its catalytic application towards epoxidation of olefins
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Abstract: A novel ionic liquid (IL) based on catalytic functional metal rhenium, [Smim][ReO4] (1-heptyl-3-methyl-imidazolium perrhenate) was synthesized and characterized. Density and surface tension values of the IL were determined at different temperatures, and the volume and surface properties were calculated and discussed, respectively. Furthermore, the synthesized ionic liquid [Smim][ReO4] was used as a green solvent and catalyst for homogeneous catalyzed epoxidation of olefin with urea hydrogen peroxide (UHP) oxidant. The effect of factors of catalyst, oxidant, reaction time, and reaction temperature was discussed. The conversion of cyclohexene and cyclooctene is over 99% at optimum conditions. The IL [Smim][ReO4] as catalyst and solvent are characterized by high efficiency, long service life and recoverability, which is a better green homogeneous catalyst for epoxidation of olefins. Graphic Abstract: A novel IL based on catalytic functional metal rhenium, [Smim][ReO4] was synthesized and characterized. The volume and surface properties were calculated and discussed by the density and surface tension values at different temperatures, respectively. Furthermore, the as-synthesized [Smim][ReO4] was used as a green solvent and catalyst for homogeneous catalyzed epoxidation of olefin with urea hydrogen peroxide (UHP) oxidant. The results showed that the yield and selectivity of the reaction were up to 99%, and the catalytic efficiency of [Smim][ReO4] did not decrease significantly after five times recycling. Easy separation, recycle, nontoxicity and homogeneous catalysis are the main advantages of perrhenate ionic liquids over other heterogeneous catalysts containing organic solvents.[Figure not available: see fulltext.].
- Song, Zongren,Liu, Xueke,Zhang, Hao,Fang, Dawei,Ma, Xiaoxue
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- Aldehyde-catalyzed epoxidation of unactivated alkenes with aqueous hydrogen peroxide
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The organocatalytic epoxidation of unactivated alkenes using aqueous hydrogen peroxide provides various indispensable products and intermediates in a sustainable manner. While formyl functionalities typically undergo irreversible oxidations when activating an oxidant, an atropisomeric two-axis aldehyde capable of catalytic turnover was identified for high-yielding epoxidations of cyclic and acyclic alkenes. The relative configuration of the stereogenic axes of the catalyst and the resulting proximity of the aldehyde and backbone residues resulted in high catalytic efficiencies. Mechanistic studies support a non-radical alkene oxidation by an aldehyde-derived dioxirane intermediate generated from hydrogen peroxide through the Payne and Criegee intermediates.
- Kokotos, Christoforos G.,Kokotou, Maroula G.,Lotter, Dominik,Sparr, Christof,Triandafillidi, Ierasia
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p. 10191 - 10196
(2021/08/12)
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- Replacement of volatile acetic acid by solid sio2@cooh silica (Nano)beads for (ep)oxidation using mn and fe complexes containing bpmen ligand
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Mn and Fe BPMEN complexes showed excellent reactivity in catalytic oxidation with an excess of co-reagent (CH3COOH). In the straight line of a cleaner catalytic system, volatile acetic acid was replaced by SiO2 (nano)particles with two different sizes to which pending carboxylic functions were added (SiO2@COOH). The SiO2@COOH beads were obtained by the functionaliza-tion of SiO2 with pending nitrile functions (SiO2@CN) followed by CN hydrolysis. All complexes and silica beads were characterized by NMR, infrared, DLS, TEM, X-ray diffraction. The replacement of CH3COOH by SiO2@COOH (100 times less on molar ratio) has been evaluated for (ep)oxi-dation on several substrates (cyclooctene, cyclohexene, cyclohexanol) and discussed in terms of activity and green metrics.
- Agustin, Dominique,Daran, Jean-Claude,Gayet, Florence,Guillo, Pascal,Wang, Yun
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- Vapor-Phase Cyclohexene Epoxidation by Single-Ion Fe(III) Sites in Metal-Organic Frameworks
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Heterogeneous catalysts supported on metal-organic frameworks (MOFs), which possess uniform porosity and crystallinity, have attracted significant interest for recent years due to the ease of active-site characterization via X-ray diffraction and the subs
- Otake, Ken-Ichi,Ahn, Sol,Knapp, Julia,Hupp, Joseph T.,Notestein, Justin M.,Farha, Omar K.
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supporting information
p. 2457 - 2463
(2021/02/16)
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- A method for preparation of cycloalkane diols
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The present invention provides a process for preparing cycloalkane diols. In detail, the process for preparing cycloalkane diols of the present invention comprises contacting a gaseous oxidizer and cycloalkene with MIL metal - organic frameworks to produce cycloalkane diols.
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Paragraph 0058-0083
(2021/06/09)
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- Structural and Biochemical Studies Enlighten the Unspecific Peroxygenase from Hypoxylon sp. EC38 as an Efficient Oxidative Biocatalyst
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Unspecific peroxygenases (UPOs) are glycosylated fungal enzymes that can selectively oxidize C-H bonds. UPOs employ hydrogen peroxide as the oxygen donor and reductant. With such an easy-to-handle cosubstrate and without the need for a reducing agent, UPOs are emerging as convenient oxidative biocatalysts. Here, an unspecific peroxygenase from Hypoxylon sp. EC38 (HspUPO) was identified in an activity-based screen of six putative peroxygenase enzymes that were heterologously expressed in Pichia pastoris. The enzyme was found to tolerate selected organic solvents such as acetonitrile and acetone. HspUPO is a versatile catalyst performing various reactions, such as the oxidation of prim- and sec-alcohols, epoxidations, and hydroxylations. Semipreparative biotransformations were demonstrated for the nonenantioselective oxidation of racemic 1-phenylethanol rac-1b (TON = 13 000), giving the product with 88% isolated yield, and the oxidation of indole 6a to give indigo 6b (TON = 2800) with 98% isolated yield. HspUPO features a compact and rigid three-dimensional conformation that wraps around the heme and defines a funnel-shaped tunnel that leads to the heme iron from the protein surface. The tunnel extends along a distance of about 12 ? with a fairly constant diameter in its innermost segment. Its surface comprises both hydrophobic and hydrophilic groups for dealing with substrates of variable polarities. The structural investigation of several protein-ligand complexes revealed that the active site of HspUPO is accessible to molecules of varying bulkiness with minimal or no conformational changes, explaining the relatively broad substrate scope of the enzyme. With its convenient expression system, robust operational properties, relatively small size, well-defined structural features, and diverse reaction scope, HspUPO is an exploitable candidate for peroxygenase-based biocatalysis.
- Ebner, Katharina,Glieder, Anton,Kroutil, Wolfgang,Mattevi, Andrea,Rinnofner, Claudia,Rotilio, Laura,Swoboda, Alexander
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p. 11511 - 11525
(2021/09/22)
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- Structural elucidation, DFT calculations and catalytic activity of dioxomolybdenum(VI) complexes with N–N donor ligand: Role of halogen atom coordinated to the molybdenum centre
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Two new isostructural mononuclear dioxomolybdenum(VI) complexes of the formula MoO2X2L [where, X = Cl (1), Br (2)] have been synthesized with a N–N donor 2-(3-methyl-5-phenyl pyrazol-1-yl) benzthiazole ligand (L). The reaction is carried out in open air and the MoVO3+ centre in the precursor molecule, MoOX3L undergoes spontaneous aerial oxidation, leading to the formation of molybdenum(VI) complexes 1 and 2. The complexes are characterized by a wide range of spectroscopic techniques (IR, UV–Vis and 1H NMR) and elemental analyses. Crystal structures of the ligand and complexes 1 and 2 have been determined by single crystal X-ray diffraction which reveal a distorted octahedral geometry around the molybdenum(VI) centre in both the complexes. The ligand and the complexes build up fascinating supramolecular assembly via several non-covalent interactions including hydrogen bonding, C–H···π and π···π interactions. Further, a detailed study of Hirshfeld surface analysis and fingerprint plots of complexes 1 and 2 are presented for understanding the intermolecular interactions involved in building self-assembled frameworks. Supportive DFT and TD-DFT calculations have also been carried out. Electrochemical properties of the complexes have been examined by cyclic voltammetry. Catalytic performance of the synthesized complexes has been evaluated for the oxidation of different olefins in the presence of hydrogen peroxide.
- Roy, Malini,Biswal, Debanjana,Pramanik, Nikhil Ranjan,Drew, Michael G.B.,Paul, Suvendu,Kachhap, Payal,Haldar, Chanchal,Chakrabarti, Syamal
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- Activation of H2O2over Zr(IV). Insights from Model Studies on Zr-Monosubstituted Lindqvist Tungstates
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Zr-monosubstituted Lindqvist-type polyoxometalates (Zr-POMs), (Bu4N)2[W5O18Zr(H2O)3] (1) and (Bu4N)6[{W5O18Zr(μ-OH)}2] (2), have been employed as molecular models to unravel the mechanism of hydrogen peroxide activation over Zr(IV) sites. Compounds 1 and 2 are hydrolytically stable and catalyze the epoxidation of C?C bonds in unfunctionalized alkenes and α,β-unsaturated ketones, as well as sulfoxidation of thioethers. Monomer 1 is more active than dimer 2. Acid additives greatly accelerate the oxygenation reactions and increase oxidant utilization efficiency up to >99%. Product distributions are indicative of a heterolytic oxygen transfer mechanism that involves electrophilic oxidizing species formed upon the interaction of Zr-POM and H2O2. The interaction of 1 and 2 with H2O2 and the resulting peroxo derivatives have been investigated by UV-vis, FTIR, Raman spectroscopy, HR-ESI-MS, and combined HPLC-ICP-atomic emission spectroscopy techniques. The interaction between an 17O-enriched dimer, (Bu4N)6[{W5O18Zr(μ-OCH3)}2] (2′), and H2O2 was also analyzed by 17O NMR spectroscopy. Combining these experimental studies with DFT calculations suggested the existence of dimeric peroxo species [(μ-?2:?2-O2){ZrW5O18}2]6- as well as monomeric Zr-hydroperoxo [W5O18Zr(?2-OOH)]3- and Zr-peroxo [HW5O18Zr(?2-O2)]3- species. Reactivity studies revealed that the dimeric peroxo is inert toward alkenes but is able to transfer oxygen atoms to thioethers, while the monomeric peroxo intermediate is capable of epoxidizing C?C bonds. DFT analysis of the reaction mechanism identifies the monomeric Zr-hydroperoxo intermediate as the real epoxidizing species and the corresponding α-oxygen transfer to the substrate as the rate-determining step. The calculations also showed that protonation of Zr-POM significantly reduces the free-energy barrier of the key oxygen-transfer step because of the greater electrophilicity of the catalyst and that dimeric species hampers the approach of alkene substrates due to steric repulsions reducing its reactivity. The improved performance of the Zr(IV) catalyst relative to Ti(IV) and Nb(V) catalysts is respectively due to a flexible coordination environment and a low tendency to form energy deep-well and low-reactive Zr-peroxo intermediates.
- Abramov, Pavel A.,Carbó, Jorge J.,Chesalov, Yuriy A.,Eltsov, Ilia V.,Errington, R. John,Evtushok, Vasilii Yu.,Glazneva, Tatyana S.,Ivanchikova, Irina D.,Kholdeeva, Oxana A.,Maksimchuk, Nataliya V.,Maksimov, Gennadii M.,Poblet, Josep M.,Solé-Daura, Albert,Yanshole, Vadim V.,Zalomaeva, Olga V.
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p. 10589 - 10603
(2021/09/02)
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- Liquid-Phase Cyclohexene Oxidation with O2 over Spray-Flame-Synthesized La1?xSrxCoO3 Perovskite Nanoparticles
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La1?xSrxCoO3 (x=0, 0.1, 0.2, 0.3, 0.4) nanoparticles were prepared by spray-flame synthesis and applied in the liquid-phase oxidation of cyclohexene with molecular O2 as oxidant under mild conditions. The catalysts were systematically characterized by state-of-the-art techniques. With increasing Sr content, the concentration of surface oxygen vacancy defects increases, which is beneficial for cyclohexene oxidation, but the surface concentration of less active Co2+ was also increased. However, Co2+ cations have a superior activity towards peroxide decomposition, which also plays an important role in cyclohexene oxidation. A Sr doping of 20 at. % was found to be the optimum in terms of activity and product selectivity. The catalyst also showed excellent reusability over three catalytic runs; this can be attributed to its highly stable particle size and morphology. Kinetic investigations revealed first-order reaction kinetics for temperatures between 60 and 100 °C and an apparent activation energy of 68 kJ mol?1 for cyclohexene oxidation. Moreover, the reaction was not affected by the applied O2 pressure in the range from 10 to 20 bar. In situ attenuated total reflection infrared spectroscopy was used to monitor the conversion of cyclohexene and the formation of reaction products including the key intermediate cyclohex-2-ene-1-hydroperoxide; spin trap electron paramagnetic resonance spectroscopy provided strong evidence for a radical reaction pathway by identifying the cyclohexenyl alkoxyl radical.
- Büker, Julia,Alkan, Baris,Chabbra, Sonia,Kochetov, Nikolai,Falk, Tobias,Schnegg, Alexander,Schulz, Christof,Wiggers, Hartmut,Muhler, Martin,Peng, Baoxiang
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supporting information
p. 16912 - 16923
(2021/10/19)
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- Evaluation of the protolytic equilibria and catalytic activity of sugar-based Schiff base ligands with VO2+ and MoO22+ cations in sulfoxidation and epoxidation reactions
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Based on the two anomeric methyl 3-amino-2,3-dideoxy-D-arabino-hexopyranosides ten new sugar-modified Schiff base ligands have been synthesized after monocondensation reaction with five o-hydroxyaromatic aldehydes, i.e. salicylaldehyde and its five para-s
- Chylewska, Agnieszka,D?browska, Aleksandra,Karman, Marta,Madejska, Katarzyna,Romanowski, Grzegorz
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- Lipase catalysed oxidations in a sugar-derived natural deep eutectic solvent
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Chemoenzymatic oxidations involving the CAL-B/H2O2 system was developed in a sugar derived Natural Deep Eutectic Solvent (NaDES) composed by a mixture of glucose, fructose and sucrose. Good to excellent conversions of substrates like cyclooctene, limonene, oleic acid and stilbene to their corresponding epoxides, cyclohexanone to its corresponding lactone and 2-phenylacetophenone to its corresponding ester, demonstrate the viability of the sugar NaDES as a reaction medium for epoxidation and Baeyer-Villiger oxidation.
- Vagnoni, Martina,Samorì, Chiara,Pirini, Daniele,Vasquez De Paz, Maria Katrina,Gidey, Dawit Gebremichael,Galletti, Paola
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- Demonstrating the Critical Role of Solvation in Supported Ti and Nb Epoxidation Catalysts via Vapor-Phase Kinetics
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Catalytic oxidation of hydrocarbons with hydrogen peroxide (H2O2) has been of the utmost importance for several decades. The vast majority of studies have been performed in the condensed phase, even though condensed phases introduce complex solvent effects and can promote the leaching of active sites. In response, we have built a custom reactor system to understand H2O2 activation and selective oxidation in the vapor-phase. In this report, we study the epoxidation of cyclohexene with H2O2 over four Lewis-acidic metal oxide catalysts: Ti and Nb grafted on SiO2 and on the Zr based metal-organic framework, NU-1000. The M-SiO2 materials are highly selective to the formation of epoxides and diols, as they can be in the condensed phase, while the NU-1000 based materials are far more prone to overoxidation to CO2, which appears to be connected to their strong reactant adsorption. Apparent activation energies are calculated for all materials when operating in the same kinetic regime, and the heats of cyclohexene adsorption into their pores are then used to directly compare intrinsic enthalpies of activation in the vapor vs condensed phase for the M-SiO2 catalysts. Nb-SiO2 catalysts exhibit similar intrinsic enthalpies of activation in the vapor and condensed phases, whereas the condensed phase transition state in Ti-SiO2 is 24 kJ/mol lower in energy than that of the same material in the vapor phase. These experiments establish another methodology for understanding the various roles of solvent in selective oxidation reactions and studying these reactions under conditions that differ significantly from the thousands of prior studies in the condensed phase.
- Ahn, Sol,Ardagh, M. Alexander,Farha, Omar K.,Hicks, Kenton E.,Nauert, Scott L.,Notestein, Justin M.,Schweitzer, Neil M.
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p. 2817 - 2825
(2020/03/11)
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- Homo-dinuclear VO2+ and Ni2+ dihydrazone complexes: Synthesis, characterization, catalytic activity and CO2-corrosion inhibition under sustainable conditions
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VO2+ and Ni2+ complexes (VOPHL and NiPHL) were prepared by complexation of terephthaloyl salicylidene dihydrazone (H2PHL) with VO2+ or Ni2+ ions. The chemical structures were estimated by various spectroscopic methods. Their sustainable corrosion inhibition on mild steel in NaCl solutions saturated with CO2 was investigated using potentiodynamic polarization (PDP), open circuit potential and electrochemical impedance spectroscopy (EIS) methods. H2PHL, NiPHL and VOPHL showed maximum capacity within 89.57, 97.25 and 98.22%, respectively. The PDP study refers to that they could act as mixed-type inhibitors i.e. retarded both cathodic and anodic reactions. Metal complexes displayed better inhibition than their coordinated ligand. H2PHL and its M-complexes adsorbed on C-steel surface via chemical adsorption with obeying the Langmuir model. The post-exposure investigation, for the inhibited and uninhibited C-steel surface, was elucidated using SEM /EDS. The homogeneous catalytic behavior of NiPHL and VOPHL was studied in the (ep)oxidation of unsaturated cycloalkene (1,2-cyclohexene) and Suzuki-Miyaura cross-coupling. VOPHL shows better catalytic potential in (ep)oxidation processes. NiPHL has higher catalytic efficiency towards cross-couplings. The aqueous hydrolysis of epoxy selective product could be reduced in low temperature of the (ep)oxidation processes. DFT studies were performed on H2PHL, NiPHL and VOPHL. Electronic representatives ELUMO, EHOMO energy gap (ΔE), hardness, softness and electronegativity were computed. Theoretical values are in good accordance with corrosive and catalytic experimental results.
- Adam, Mohamed Shaker S.,Soliman, Kamal A.,Abd El-Lateef, Hany M.
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- Cu(ii)Cl2containing bispyridine-based porous organic polymer support preparedviaalkyne-azide cycloaddition as a heterogeneous catalyst for oxidation of various olefins
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A new type of porous organic polymer (POP) based heterogeneous catalystCu-POPwas prepared by immobilizing Cu(ii)Cl2into bpy containing POP preparedviaalkyne-azide cycloaddition. This new catalyst showed efficient catalytic activities and outstanding reusability. Remarkably, one batch ofCu-POPwas continuously used for all olefins without losing its activity by simply washing.
- Choi, Hye Min,Lee, Suk Joong,Yoon, Jongho
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supporting information
p. 9149 - 9152
(2020/06/17)
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- Chiral cis-dioxidomolybdenum(VI) complexes with Schiff bases possessing two alkoxide groups: Synthesis, structure, spectroscopic studies and their catalytic activity in sulfoxidation and epoxidation
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New chiral mononuclear cis-dioxidomolybdenum(VI) complexes, [MoO2(HL1-9)] and [MoO2(HL10)(CH3OH)], have been synthesized by the reaction of MoO2(acac)2 with tetradentate Schiff bases derived from various substituted salicylaldehydes and R(+)-3-amino-1,2-propanediol. All complexes have been characterized by elemental analysis, circular dichroism, electronic, IR and NMR (1H, 13C) spectroscopy. The molecular and crystal structure of [MoO2(HL10)(CH3OH)] elucidated by single-crystal X-ray diffraction revealed a six-coordinate distorted octahedral geometry and coordination of methanol molecule leaving one hydroxyl group uncoordinated. Surprisingly, NMR measurements made for [MoO2(HL1-9)] undoubtedly show that Schiff bases behave as dibasic tetradentate ONOO donor ligands and no solvent coordination has been observed. The catalytic activity studies have been also performed for all complexes in asymmetric sulfoxidation of thioanisole and epoxidation of styrene, cyclohexene and two monoterpenes, i.e. S(?)-limonene and (?)-α-pinene, using aqueous 30% H2O2 or tert-butyl hydroperoxide (TBHP) as the oxygen source.
- Karman, Marta,Romanowski, Grzegorz,Wera, Micha?
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- Immobilization of gold on short-channel mesoporous SBA-15 functionalized with thiol and hydrophobic groups for oxidation reactions
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Nanosized gold entities immobilized on short-channel SBA-15 mesoporous materials functionalized solely with mercaptopropyl groups and together with propyl and octyl moieties have been prepared following a two-steps procedure. These materials have been used as catalysts for the oxidation of cyclohexene with molecular oxygen in liquid phase at atmospheric pressure. First, SBA-15 materials functionalized only with mercaptopropyl groups and with a combination of these groups with two hydrophobic moieties, namely propyl and octyl, have been synthesized in the presence of the non-ionic surfactant P104. Small particles having short channel length have been identified by TEM and SEM. In order to study the influence of the nature of the sulphur functional group, these S-bearing materials were also oxidized with hydrogen peroxide or dimethyldioxirane (DMD) to sulfonic groups prior to gold immobilization. The effectiveness of these oxidation methods was assessed by 29Si MAS NMR, 13C CP MAS NMR, XPS, chemical and thermal analysis, and it has been found that DMD oxidized efficiently thiol groups to sulfonic groups, but H2O2 leaves a fraction of unreacted thiol. In a second step, nanosized gold entities have been prepared by a two-liquid phases route involving rosemary oil as organic phase and an aqueous phase formed by dissolving gold in a solution of ammonium chloride in concentrated nitric acid (aqua regia). Following this method, a fraction of the Au dissolved in the aqua regia solution is spontaneously reduced and transferred to the essential oil phase. Upon contacting the gold-bearing organic layer with the mesoporous materials, gold is actually immobilized on them, rendering metal contents in the range 1.1-0.2 wt.percent, being those functionalized with alkyl chains the least efficient in capturing gold from the organic phase. No surface plasmon resonance band at 520 nm characteristic of gold nanoparticles has been detected by UV–vis spectroscopy in these Au-containing materials. All of them are active and selective for the allylic oxidation of cyclohexene, but their specific activity varies as a function of the nature of the functional groups. It has been found that the most active catalysts are those pre-oxidized with DMD. The presence of hydrophobic octyl groups increases substantially the turnover number of the reaction (TON), while the short-chain propyl moieties hardly affect the activity. It has been found that the nanosized gold entities initially present in the catalysts evolve in the reaction medium towards the formation of nanoparticles.
- de la Serna Valdés,Agúndez,Márquez-álvarez,Pérez-Pariente
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- Double end-on azido derivative of a tridentate (NNO) Schiff base dimeric copper(II) complex: synthesis, X-ray structure, magnetic property and catalytic effectiveness
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A dimeric copper(II) complex, bis{(2-[1-(aminoethylimino)ethyl]-phenoxo}-di-μ1,1-azido-dicopper(II), [Cu2(L)2(μ2-1,1-N3)2] (1) [L = 2-[1-(aminoethylimino)ethyl]-phenoxo ion], has been isolated using a self-assembly reaction using a 1:1:1 molar ratio of Cu(NO3)2·3H2O, HL and NaN3 in methanol at room temperature and characterized through X-ray diffraction analysis and spectroscopic studies. X-ray structural analysis reveals that 1 consists of two distinct dinuclear molecular units, where each copper(II) center in the individual dinuclear unit adopts a distorted square pyramidal geometry with a CuN4O chromophore ligated through a tridentate (NNO) Schiff base and two N atoms of two different bridging azides in μ1,1-mode. Two Cu(II) centers are linked through double μ2-1,1-N3 bridges to form the dinuclear unit [Cu2(L)2(μ2-1,1-N3)2]. In the crystalline state, the dinuclear units in 1 are associated through weak intermolecular N-H?O hydrogen bonds to afford a 2-D sheet structure viewed along the crystallographic a-axis. The small magnitude of the antiferromagnetic interaction (J = –0.45 cm?1) is a result of the long Cu···Cu separation (3.205(2) ?). The catalytic efficacy of 1 was studied in a series of solvents for the epoxidation of alkenes using tert-butyl-hydroperoxide (TBHP) as an efficient oxidant under mild conditions.
- Chowdhury, Habibar,Bera, Rajesh,Rizzoli, Corrado,Adhikary, Chandan
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p. 3062 - 3078
(2020/10/29)
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- Amino-Induced 2D Cu-Based Metal–Organic Framework as an Efficient Heterogeneous Catalyst for Aerobic Oxidation of Olefins
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With the assistance of hydrogen bonds of the o-amino group, we have successfully tuned a coordination structure from a metal–organic polyhedron (MOP) to a two-dimensional (2D) metal–organic framework (MOF). The amino group forms hydrogen bonds with the two vicinal carboxylic groups, and induces the ligand to coordinate with copper ions to form the 2D structure. The obtained 2D Cu-based MOF (Cu-AIA) has been applied as an efficient heterogeneous catalyst in the aerobic epoxidation of olefins by using air as oxygen source. Without the aggregation problem of active sites in MOPs, Cu-AIA possesses much higher reactivity than MOP-1. Furthermore, the amino group of the framework has been used as a modifiable site through post-synthetic metalation (PSMet) to prepare a 2D MOF-supported Pd single-site heterogeneous catalyst, which shows excellent catalytic performance for the Suzuki reaction. It indicates that Cu-AIA can also work as a good 2D MOF carrier for the derivation of other heterogeneous catalysts.
- Bao, Shixiong,Cai, Mengke,Ding, Shujiang,Li, Guangqin,Tang, Jia,Tao, Jinzhang,Wang, Xiaoxia,Xie, Guanqun
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supporting information
(2020/03/13)
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- Rare earth metal compound, preparation method, composition, and method for catalyzing epoxidation of olefin
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The invention relates to a rare earth metal compound and application thereof in catalyzing epoxidation of olefin. The rare earth metal compound disclosed by the invention has a structure as shown in aformula E. The invention also relates to a preparation method of the rare earth metal compound and a composition containing the rare earth metal compound. The method is characterized in that a rare earth metal compound is added into the reaction, so that the dosage of a molybdenum catalyst can be reduced. Olefin and organic peroxide react under the action of a catalyst to generate epoxide, the organic peroxide is converted into corresponding alcohol, and the conversion rate of the organic peroxide is larger than 99%. After the reaction is finished, the rare earth metal compound can be separated and recycled. The method has the advantages of simple process, high catalytic system activity, effective reduction of the use amount of the catalyst while guaranteeing the catalytic efficiency, andcost saving.
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Paragraph 0082-0083
(2020/07/24)
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- Magnetically recoverable porphyrin-based nanocatalysts for the effective oxidation of olefins with hydrogen peroxide: A comparative study
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In this paper, preparation, characterization and catalytic applications of metalloporphyrin-based magnetic nanocatalysts were investigated. meso-Tetrakis(4-carboxyphenyl)porphyrinatoiron(iii) chloride (Fe(TCPP)Cl) and meso-tetrakis(4-carboxyphenyl)porphyrinatomanganese(iii) acetate (Mn(TCPP)OAc) were separately immobilized onto the surface of amine functionalized magnetic nanoparticles (Fe3O4/SiO2/NH2) via covalent attachment. The obtained nanocatalysts were characterized using FT-IR and UV-Vis and atomic absorption spectroscopy, X-ray powder diffraction (XRD), vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). The catalytic efficiency of Fe3O4/SiO2/NH2-Fe(TCPP)Cl and Fe3O4/SiO2/NH2-Mn(TCPP)OAc for the green oxidation of alkenes with H2O2 was investigated in a comparative manner. The Mn-porphyrin based magnetic nanocatalyst shows higher catalytic efficiency compared to the Fe-porphyrin. In addition, the prepared magnetic nanocatalyst exhibited excellent reusability and could be reused at least five times without significant leaching or loss of activity. This journal is
- Rayati, Saeed,Moradi, Dana,Nejabat, Fatemeh
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p. 19385 - 19392
(2020/11/23)
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- Cerium Oxide Nanoparticles Inside Carbon Nanoreactors for Selective Allylic Oxidation of Cyclohexene
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The confinement of cerium oxide (CeO2) nanoparticles within hollow carbon nanostructures has been achieved and harnessed to control the oxidation of cyclohexene. Graphitized carbon nanofibers (GNF) have been used as the nanoscale tubular host and filled by sublimation of the Ce(tmhd)4 complex (where tmhd = tetrakis(2,2,6,6-Tetramethyl-3,5-heptanedionato)) into the internal cavity, followed by a subsequent thermal decomposition to yield the hybrid nanostructure CeO2?GNF, where nanoparticles are preferentially immobilized at the internal graphitic step-edges of the GNF. Control over the size of the CeO2 nanoparticles has been demonstrated within the range of about 4-9 nm by varying the mass ratio of the Ce(tmhd)4 precursor to GNF during the synthesis. CeO2?GNF was effective in promoting the allylic oxidation of cyclohexene in high yield with time-dependent control of product selectivity at a comparatively low loading of CeO2 of 0.13 mol %. Unlike many of the reports to date where ceria catalyzes such organic transformations, we found the encapsulated CeO2 to play the key role of radical initiator due to the presence of Ce3+ included in the structure, with the nanotube acting as both a host, preserving the high performance of the CeO2 nanoparticles anchored at the GNF step-edges over multiple uses, and an electron reservoir, maintaining the balance of Ce3+ and Ce4+ centers. Spatial confinement effects ensure excellent stability and recyclability of CeO2?GNF nanoreactors.
- Agasti, Nityananda,Astle, Maxwell A.,Rance, Graham A.,Alves Fernandes, Jesum,Dupont, Jairton,Khlobystov, Andrei N.
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p. 1161 - 1171
(2020/03/10)
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- Sulfonic-functionalized MIL-101 as bifunctional catalyst for cyclohexene oxidation
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Metal-organic frameworks (MOFs) are newly emerging and versatile platforms for designing catalysts, and catalytic oxidation of cyclohexene has attracted much academic and industrial attention for the versatile reactivity of the substrate and the great importance of the various oxygenated products. Here we report the bifunctional catalytic properties of a sulfonic-containing MOF, MIL-101-SO3H, for cyclohexene oxidation. The sulfonic group and the Cr(III) site acts in a complementary or collaborative way. The Cr(III) framework promotes the oxidation to 3-hydroperoxycyclohex-1-ene (perox) and 2-cyclohexen-1-one (1-one) (route A), whereas the sulfonic group in collaboration with the Cr(III) framework promotes the oxidation to diol (route B) and also enhances further conversions in route A: from perox to 1-one, to 2-cyclohexen-1,4-dione (dione) and even to benzoquinone. With the bifunctional MOF, molecular oxygen alone cannot oxidize cyclohexene but participates as oxidant cooperating with tert-butyl hydroperoxide (TBHP) to accelerate the reactions and to alter the product distribution in favor of dione.
- Sun, Weng-Jie,Gao, En-Qing
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- Cyclohexene epoxidation with H2O2in the vapor and liquid phases over a vanadium-based metal-organic framework
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A metal-organic framework, MIL-47(V) containing coordinatively saturated V+IV sites linked together by terephthalic linkers, was prepared by a solvothermal method and evaluated as a catalyst in the epoxidation of cyclohexene. We have compared the catalytic activity in the condensed and gas phase oxidation of cyclohexene to discuss the effect of temperature and reaction phase in cyclohexene epoxidation over MIL-47(V). The catalysts were examined for the epoxidation of cyclohexene with H2O2 at 50, 65, 120, and 150 °C. We observed significant differences in product selectivity between liquid-phase and gas-phase operations and confirmed that the active sites are tightly incorporated into the MOF as node channels and thus resistant to leaching.
- Ahn, Sol,Bae, Youn-Sang,Farha, Omar K.,Kim, Ah-Reum,Notestein, Justin M.,Yoon, Tae-Ung
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p. 4580 - 4585
(2020/08/10)
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- Selective cyclohexene oxidation with O2, H2O2and: Tert -butyl hydroperoxide over spray-flame synthesized LaCo1- x Fex O3nanoparticles
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The elimination of waste and by-product generation and reduced dependence on hazardous chemicals are the key steps towards environmentally sustainable chemical transformations. Heterogeneously catalysed oxidation of cyclohexene with environmentally friendly oxidizing agents such as O2, H2O2 and tert-butyl hydroperoxide (TBHP) has great potential to replace existing processes using stoichiometric oxidants. A series of spray-flame synthesised nanoparticulate LaCo1-xFexO3 catalysts was employed for cyclohexene oxidation, and the comparative results showed that TBHP led to the highest initial activity and allylic selectivity, but O2 resulted in higher conversion for longer reaction times. Furthermore, the influence of Fe substitution was studied, which did not show any beneficial synergistic effects. LaCoO3 was found to be the optimum catalyst for cyclohexene oxidation with O2, following first-order reaction kinetics with an apparent activation energy of 57 kJ mol-1. The catalyst showed good reusability due to its highly stable particle size, morphology and perovskite structure. 7-Oxabicyclo[4.1.0]heptan-2-one was identified to be formed by the oxidation of 2-cyclohexene-1-one with 2-cyclohexene-1-hydroperoxide.
- Alkan, Baris,Büker, Julia,Falk, Tobias,Fu, Qi,Muhler, Martin,Peng, Baoxiang,Schulwitz, Jonas,Schulz, Christof,Waffel, Daniel,Wiggers, Hartmut,Xia, Wei
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p. 5196 - 5206
(2020/08/19)
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- Biochar as supporting material for heterogeneous Mn(II) catalysts: Efficient olefins epoxidation with H2O2
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A novel type of hybrid catalytic materials [MnII-L?BC] has been developed using biochar (BC) as support material for covalent grafting of a MnII Schiff-base catalyst (MnII-L). The hybrid [MnII-L?BC] materials have been evaluated for an important catalytic process, epoxidation of olefins using H2O2 as oxidant. A number of different substrates were used, with cyclohexene achieving the highest yields. When compared to the non-grafted, homogeneous MnII-L, the hybrid catalysts [MnII-L?BC] show a significant enhancement of the catalytic efficiency i.e. as documented by the increase of Turnover Numbers (TONs) (826 for [MnII-L-SS550ox] and 822 for [MnII-L-SW550ox]) and Turnover Frequencies (TOFs) (551 h?1 for [MnII-L-SS550ox] and 411 h?1 for [MnII-L-SW550ox]). The interfacial catalytic mechanism and the role of the BC support have been analyzed by Raman and Electron Paramagnetic Resonance spectroscopies. Based on these data we discuss a mechanism where the high efficiency of the hybrid materials involves the biochar carbon layers acting as promoters of the substrate and products kinetics. To a broader context, this work exemplifies that biochar-based hybrid materials are potent for oxidative catalysis technologies.
- Borges Regitano, Jussara,Deligiannakis, Yiannis,Gemenetzi, Aikaterini,Louloudi, Maria,Mavrogiorgou, Alexandra,Pierri, Leticia
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- Catalytic oxidation of cyclohexene by supported gold nanoclusters synthesized in a two-liquid phases system containing eucalyptus essential oil
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Gold nanoclusters (d p = 6.3 nm, 3.5 wt% S) was contacted with aliquots of the Au-containing essential oil phase taken at 1, 3, 6 and 8 days of contact time between both phases. In this way, gold was immobilized on the support, ranging from 0.4 wt% for the 1-day sample, to 2.7 wt% in the 3-days material. UV–vis spectra show the presence of gold nanoclusters in these samples, but the surface plasmon resonance at 520 cm?1, characteristic of Au nanoparticles, was not detected save for the 3-days sample. 13C MAS NMR and TG evidence that the thiol groups of the support remain mostly unaltered for the 1-day sample, but oxidation to sulfonic acid groups becomes apparent for contact time > 3 days, and reaches nearly 60 % of the total sulphur species after 8 days of contact time as estimated from XPS analysis. The Au-SH-bearing catalyst is inactive for cyclohexene oxidation with molecular oxygen in liquid phase, but those having sulfonic groups are active and selective for its allylic oxidation. It has been found for the 8-day catalyst that the gold nanoclusters partially evolve spontaneously in the reaction medium to form gold nanoparticles, and this agglomeration process parallels the increase in catalyst activity.
- Agúndez, J.,Ares, C.,Márquez-álvarez, C.,Pérez-Pariente, J.
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- Effect of Ligand Fields on the Reactivity of O2-Activating Iron(II)-Benzilate Complexes of Neutral N5 Donor Ligands
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Three new iron(II)-benzilate complexes [(N4Py)FeII(benzilate)]ClO4 (1), [(N4PyMe2)FeII(benzilate)]ClO4 (2) and [(N4PyMe4)FeII(benzilate)]ClO4 (3) of neutral pentadentate nitrogen donor ligands have been isolated and characterized to study their dioxygen reactivity. Single-crystal X-ray structures reveal a mononuclear six-coordinate iron(II) center in each case, where benzilate binds to the iron center in monodentate mode via one carboxylate oxygen. Introduction of methyl groups in the 6-positions of the pyridine rings makes the N4PyMe2 and N4PyMe4 ligand fields weaker compared to that of the parent N4Py ligand. All the complexes (1–3) react with dioxygen to decarboxylate the coordinated benzilate to benzophenone quantitatively. The decarboxylation is faster for the complex of the more sterically hindered ligand and follows the order 3>2>1. The complexes display oxygen atom transfer reactivity to thioanisole and also exhibit hydrogen atom transfer reactions with substrates containing weak C?H bonds. Based on interception studies with external substrates, labelling experiments and Hammett analysis, a nucleophilic iron(II)-hydroperoxo species is proposed to form upon two-electron reductive activation of dioxygen by each iron(II)-benzilate complex. The nucleophilic oxidants are converted to the corresponding electrophilic iron(IV)-oxo oxidant upon treatment with a protic acid. The high-spin iron(II)-benzilate complex with the weakest ligand field results in the formation of a more reactive iron-oxygen oxidant.
- Bhattacharya, Shrabanti,Paine, Tapan Kanti,Singh, Reena
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supporting information
(2020/04/22)
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- Ionic Liquid Stabilized Niobium Oxoclusters Catalyzing Oxidation of Sulfides with Exceptional Activity
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We present here a new class of niobium oxoclusters that are stabilized effectively by carboxylate ionic liquids. These functionalized ILs are designated as [TBA][LA], [TBA][PA], and [TBA][HPA] in this work, in which TBA represents tetrabutylammonium and LA, PA, and HPA refer to lactate, propionate, 3-hydroxypropionate anions, respectively. The as-synthesized Nb oxoclusters have been characterized by use of elemental analysis, NMR, IR, XRD, TGA, HRTEM. It was found that [TBA][LA]-stabilized Nb oxoclusters (Nb?OC@[TBA][LA]) are uniformly dispersed with an average particle size of 2–3 nm and afforded exceptionally high catalytic activity for the selective oxidation of various thioethers. The turnover number with Nb?OC@[TBA][LA] catalyst was over 56 000 at catalyst loading as low as 0.0033 mol % (1 ppm). Meantime, the catalyst also showed the high activity for the epoxidation of olefins and allylic alcohols by using only 0.065 mol % of catalyst (50 ppm). The characterization of 93Nb NMR spectra revealed that the Nb oxoclusters underwent structural transformation in the presence of H2O2 but regenerated to their initial state at the end of the reaction. In particular, the highly dispersed Nb oxoclusters can absorb a large amount of polar organic solvents and thus were swollen greatly, which exhibited “pseudo” liquid phase behavior, and enabled the substrate molecules to be highly accessible to the catalytic center of Nb oxocluster units.
- Zhou, Qingqing,Ye, Man,Ma, Wenbao,Li, Difan,Ding, Bingjie,Chen, Manyu,Yao, Yefeng,Gong, Xueqing,Hou, Zhenshan
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p. 4206 - 4217
(2019/03/26)
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- Ru(III) complexes of phenoxy-imine ligands: Synthesis, characterisation and testing as oxidation catalysts
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Summary: A series of new mononuclear Ru(III) complexes bearing phenoxy-imine Schiff base tetradentate ligands (phenylimino, 4-chlore phenylimino, 3,4-dichlore phenylimino) have been prepared and characterized by elemental analysis, TGA, UV-VIS, FT-IR, 1H-NMR and 13C NMR spectra. The proposed structure of the ligands have a O2N2 core to form mononuclear Ru (III) complexes. Preliminary studies on the catalytic performances of the compounds in the cycloalkane oxydation are described. The catalytic effect of all Ru complexes results in the epoxidation reaction of cyclohexane, as shown in the substrate conversion reaction appears to be very high.
- ?apan, Ali,Ceyhan, G?khan,S?nmez, Mehmet
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p. 758 - 769
(2019/10/28)
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- Magnetically separable and reusable rGO/Fe3O4 nanocomposites for the selective liquid phase oxidation of cyclohexene to 1,2-cyclohexane diol
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A series of magnetically separable rGO/Fe3O4 nanocomposites with various amounts of graphene oxide were successfully prepared by a simple ultrasonication assisted precipitation combined with a solvothermal method and their catalytic activity was evaluated for the selective liquid phase oxidation of cyclohexene using hydrogen peroxide as a green oxidant. The prepared materials were characterized using XRD, FTIR, FESEM, TEM, HRTEM, BET/BJH, XPS and VSM analysis. The presence of well crystallized Fe3O4 as the active iron species was seen in the crystal studies of the nanocomposites. The electron microscopy analysis indicated the fine surface dispersion of spherical Fe3O4 nanoparticles on the thin surface layers of partially-reduced graphene oxide (rGO) nanosheets. The decoration of Fe3O4 nanospheres on thin rGO layers was clearly observable in all of the nanocomposites. The XPS analysis was performed to evaluate the chemical states of the elements present in the samples. The surface area of the nanocomposites was increased significantly by increasing the amount of GO and the pore structures were effectively tuned by the amount of rGO in the nanocomposites. The magnetic saturation values of the nanocomposites were found to be sufficient for their efficient magnetic separation. The catalytic activity results show that the cyclohexene conversion reached 75.3% with a highest 1,2-cyclohexane diol selectivity of 81% over 5% rGO incorporated nanocomposite using H2O2 as the oxidant and acetonitrile as the solvent at 70 °C for 6 h. The reaction conditions were further optimized by changing the variables and a possible reaction mechanism was proposed. The enhanced catalytic activity of the nanocomposites for cyclohexene oxidation could be attributed to the fast accomplishment of the Fe2+/Fe3+ redox cycle in the composites due the sacrificial role of rGO and its synergistic effect with Fe3O4, originating from the conjugated network of π-electrons in its surface structure. The rapid and easy separation of the magnetic nanocomposites from the reaction mixture using an external magnet makes the present catalysts highly efficient for the reaction. Moreover, the catalyst retained its activity for five repeated runs without any drastic drop in the reactant conversion and product selectivity.
- Pudukudy, Manoj,Jia, Qingming,Dong, Yanan,Yue, Zhongxiao,Shan, Shaoyun
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p. 32517 - 32534
(2019/10/28)
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- Trapping of a Highly Reactive Oxoiron(IV) Complex in the Catalytic Epoxidation of Olefins by Hydrogen Peroxide
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The generation of a nonheme oxoiron(IV) intermediate, [(cyclam)FeIV(O)(CH3CN)]2+ (2; cyclam=1,4,8,11-tetraazacyclotetradecane), is reported in the reactions of [(cyclam)FeII]2+ with aqueous hydrogen peroxide (H2O2) or a soluble iodosylbenzene (sPhIO) as a rare example of an oxoiron(IV) species that shows a preference for epoxidation over allylic oxidation in the oxidation of cyclohexene. Complex 2 is kinetically and catalytically competent to perform the epoxidation of olefins with high stereo- and regioselectivity. More importantly, 2 is likely to be the reactive intermediate involved in the catalytic epoxidation of olefins by [(cyclam)FeII]2+ and H2O2. In spite of the predominance of the oxoiron(IV) cores in biology, the present study is a rare example of high-yield isolation and spectroscopic characterization of a catalytically relevant oxoiron(IV) intermediate in chemical oxidation reactions.
- Engelmann, Xenia,Malik, Deesha D.,Corona, Teresa,Warm, Katrin,Farquhar, Erik R.,Swart, Marcel,Nam, Wonwoo,Ray, Kallol
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supporting information
p. 4012 - 4016
(2019/02/20)
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- 4,6-Diacetyl Resorcinol Based Vanadium(V) Complexes: Reactivity and Catalytic Applications
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Four ONO donor ligands are isolated from the condensation of 4,6-diacetyl resorcinol with isonicotinoyl hydrazide (H2dar-inh, I), nicotinoyl hydrazide (H2dar-nah, II), benzoyl hydrazide (H2dar-bhz, III), and 2-furoyl hydrazide (H2dar-fah, IV) on refluxing in MeOH. The reaction of in situ generated aqueous K[H2VVO4] with ligands I–IV at neutral pH gives complexes [K(H2O)2][VO2(dar-inh)] (1), [K(H2O)2][VO2(dar-nah)] (2), [K(H2O)2][VO2(dar-bhz)] (3), and [K(H2O)2][VO2(dar-fah)] (4), respectively. The reaction of [VIVO(acac)2] (acac = acetylacetonato) with these ligands (I–IV) under aerobic conditions in methanol yields oxidomethoxidovanadium(V) complexes [VO(OMe)(MeOH)(dar-inh)] (5), [VO(OMe)(MeOH)(dar-nah)] (6), [VO(OMe)(MeOH)(dar-bhz)] (7), and [VO(OMe)(MeOH)(dar-fah)] (8). All the isolated complexes are characterized by elemental, thermal, electrochemical, and spectroscopic techniques [FTIR, UV/Vis, NMR (1H, 13C and 51V NMR)], and single-crystal X-ray diffraction analysis (for 1, 6, 7, and 8). X-ray analysis confirms the coordination of the ligands through Ophenolate, Nazomethine, and Oenolate to the metal center. In the molecular structure of [K(H2O)(EtOH)][VVO2(dar-inh)] (abbreviated as 1a where one molecule of water is replaced by EtOH), water molecules act as bridges between two K+ ions and the complex shows a dimeric structure due to the presence of electrostatic interactions between V=O oxygen atoms with K+ ions. These complexes are active catalysts for the oxidative bromination of thymol in the presence of KBr, HClO4, and H2O2 and give 2-bromothymol, 4-bromothymol, and 2,4-dibromothymol as major products. Complexes 1–4 were also tested as catalysts for the epoxidation of various alkenes (namely styrene, cyclohexene, cis-cyclooctene, 1-hexene, 1-octene, cyclohexenone, and trans-stilbene) with H2O2 in the presence of NaHCO3 as promoter, giving the corresponding epoxides selectively.
- Maurya, Mannar R.,Jangra, Nancy,Avecilla, Fernando,Correia, Isabel
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p. 314 - 329
(2019/01/24)
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- Highly Selective and Catalytic Oxygenations of C?H and C=C Bonds by a Mononuclear Nonheme High-Spin Iron(III)-Alkylperoxo Species
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The reactivity of a mononuclear high-spin iron(III)-alkylperoxo intermediate [FeIII(t-BuLUrea)(OOCm)(OH2)]2+(2), generated from [FeII(t-BuLUrea)(H2O)(OTf)](OTf) (1) [t-BuLUrea=1,1′-(((pyridin-2-ylmethyl)azanediyl)bis(ethane-2,1-diyl))bis(3-(tert-butyl)urea), OTf=trifluoromethanesulfonate] with cumyl hydroperoxide (CmOOH), toward the C?H and C=C bonds of hydrocarbons is reported. 2 oxygenates the strong C?H bonds of aliphatic substrates with high chemo- and stereoselectivity in the presence of 2,6-lutidine. While 2 itself is a sluggish oxidant, 2,6-lutidine assists the heterolytic O?O bond cleavage of the metal-bound alkylperoxo, giving rise to a reactive metal-based oxidant. The roles of the urea groups on the supporting ligand, and of the base, in directing the selective and catalytic oxygenation of hydrocarbon substrates by 2 are discussed.
- Ghosh, Ivy,Banerjee, Sridhar,Paul, Satadal,Corona, Teresa,Paine, Tapan Kanti
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p. 12534 - 12539
(2019/08/07)
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- Allylic oxidation of olefins with a manganese-based metal-organic framework
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Selective oxidation of olefins to α,β-unsaturated ketones under mild reaction conditions has attracted considerable interest, since α,β-unsaturated ketones can serve as synthetic precursors for various downstream chemical products. The major inherent challenges with this chemical oxidation are chemo- and regio-selectivity as well as environmental concerns, i.e. catalyst recycle, safety and cost. Using atmospheric oxygen as an environmentally friendly oxidant, we found that a metal-organic framework (MOF) constructed with Mn and a tetrazolate ligand (CPF-5) showed good activity and selectivity for the allylic oxidation of olefins to α,β-unsaturated ketones. Under the optimized conditions, we could achieve 98% conversion of cyclohexene and 87% selectivity toward cyclohexanone. The combination of a substoichiometric amount of TBHP (tert-butylhydroperoxide) and oxygen not only provides a cost effective oxidation system but significantly enhances the selectivity to α,β-unsaturated ketones, outperforming most reported oxidation methods. This catalytic system is heterogeneous in nature, and CPF-5 could be reused at least five times without a significant decrease in its catalytic activity and selectivity.
- Chen, Jingwen,Chen, Minda,Zhang, Biying,Nie, Renfeng,Huang, Ao,Goh, Tian Wei,Volkov, Alexander,Zhang, Zhiguo,Ren, Qilong,Huang, Wenyu
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supporting information
p. 3629 - 3636
(2019/07/10)
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- Influence of the channel size of isostructural 3d-4f MOFs on the catalytic aerobic oxidation of cycloalkenes
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The present work reports a new group of heterogeneous catalysts with a 3D structure, CuLnIDA, {[Cu3Ln2(IDA)6]·8H2O} (Ln: LaIII, GdIII or YbIII), with an organic linker (H2IDA: iminodiacetic acid). Different sets of O2 pressure and time were used in order to obtain the optimal reaction conditions at 75 °C. The reaction was found to depend on the [aldehyde]/[substrate] ratio. The best results, with a conversion of 73% for CuLaIDA as the catalyst, were obtained for the smallest ratio of 0.2. Finally, the importance of the pore size was analysed by comparing the catalytic activity of the as formed catalyst with that of the thermally activated one. The conversion increased ca. 26-35% for the different catalysts when they were previously activated. In addition, the selectivity increased towards cyclohexenone. The use of molecular oxygen as the oxidizing agent in a system where an auxiliary solvent is not used, as the cyclohexene substrate and products play the role of a solvent, permitted us to generate a more friendly environmental system for the oxidation of cycloalkenes under mild conditions.
- Cancino, Patricio,Santiba?ez, Luis,Stevens, Christian,Fuentealba, Pablo,Audebrand, Nathalie,Aravena, Daniel,Torres, Julia,Martinez, Sebastian,Kremer, Carlos,Spodine, Evgenia
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p. 11057 - 11064
(2019/07/31)
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- Polymer immobilized tantalum(v)-amino acid complexes as selective and recyclable heterogeneous catalysts for oxidation of olefins and sulfides with aqueous H2O2
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Polymer supported heterogeneous peroxotantalum(v) catalysts were prepared by anchoring Ta(v)-diperoxo species to chloromethylated poly(styrene-divinylbenzene) resin functionalized with amino acids asparagine (l-Asn) and arginine (l-Arg). The structurally well-defined catalysts, [Ta(O2)2(L)2]--MR, [L = asparagine (catalyst 1) or arginine (catalyst 2) and MR = Merrifield resin], were comprehensively characterized by elemental analysis (CHN, ICP-OES, energy dispersive X-ray spectroscopy), spectral studies (FT-IR, Raman, 13C NMR, diffuse reflectance UV-vis and XPS), SEM, XRD, Brunauer-Emmett-Teller (BET) and thermogravimetric analysis (TGA). The supported peroxotantalum (pTa) compounds displayed excellent catalytic performance in epoxidation of alkenes with 30% H2O2, under solvent free reaction conditions. Styrene was epoxidized with >99% selectivity with the highest TOF of 1040 h-1 obtained within 30 min reaction time, whereas the TOF for norbornene epoxidation was 2000 h-1 within 1 h with >95% epoxide selectivity. Furthermore, the immobilized catalysts facilitated chemoselective oxidation of a broad range of organic sulfides to the desired sulfoxides with H2O2 in methanol, under mild reaction conditions. The oxidations proceeded with a high H2O2 efficiency percentage and are amenable to ready scalability. The heterogeneous catalysts could be easily recovered and reused for several consecutive catalytic cycles with undiminished activity/selectivity profiles in all cases. The developed catalytic strategies are operationally simple and, being free from halogenated solvent or any other toxic auxiliaries, environmentally clean.
- Saikia, Gangutri,Ahmed, Kabirun,Rajkhowa, Chandrasee,Sharma, Mitu,Talukdar, Hiya,Islam, Nashreen S.
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supporting information
p. 17251 - 17266
(2019/11/20)
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- Solvent effects on catalytic activity of manganese porphyrins with cationic, anionic and uncharged meso substituents: Indirect evidence on the nature of active oxidant species
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Oxidation of cyclohexene and styrene with sodium periodate and tetra-n-butylammonium periodate (TBAP) catalyzed by MnT(3-MePy)P(OAc), MnT(4-SO3)PP(OAc) and MnTPP(OAc) has been studied in water, methanol, acetonitrile and dichloromethane as solvents. The results show significant dependence of the product distribution on the type of solvent and the electronic nature of the aryl substituents introduced at the porphyrin periphery. While the oxidation of cyclohexene and styrene in the presence of MnT(3-MePy)P(OAc) and MnTPP(OAc) in water (also in methanol) gave the corresponding epoxides as nearly the sole product, performing the reactions in the presence of MnT(4-SO3)PP(OAc) yielded the products of allylic oxidation, cyclohexene-2-ol and cyclohexene-2-one and acetophenone as the major products. In the case of styrene, performing the reaction in the presence of MnT(4-SO3)PP(OAc), MnT(3-MePy)P(OAc) and MnTPP(OAc) in acetonitrile gave a mixture of styrene oxide and acetophenone as the products. Under the same conditions, the oxidation of cyclohexene afforded cyclohexene oxide as approximately the exclusive product. Furthermore, the oxidation of olefins in dichloromethane gave the corresponding epoxide as the exclusive products. The product distributions observed in the protic and aprotic solvents were used to provide indirect evidence on the relative contribution and reactivity of high valent manganese oxo and periodato Mn(III) porphyrin species to the oxidation reactions.
- Esfandiari bayat, Zahra,Rahiminezhad, Hajar,Zakavi, Saeed
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