- Pauson-Khand Reactions with Concomitant C?O Bond Cleavage for the Preparation of 5,5- 5,6- and 5,7-Bicyclic Ring Systems
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Pauson-Khand reactions (PKR) with concomitant C?O bond cleavage have been developed for construction of 5,5- 5,6- and 5,7-bicyclic ring systems bearing complex stereochemistry. The chemistry generates intermolecular PKR-type products in an absolute regio- and stereochemical control which is hardly achievable through real intermolecular Pauson-Khand reactions. A mechanism for this Pauson-Khand reaction has been proposed based on deuterium labelling experiments. (Figure presented.).
- Ma, Ding,Hu, Naifeng,Ao, Junli,Zang, Shaoli,Yu, Guo,Liang, Guangxin
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supporting information
p. 1887 - 1891
(2021/02/26)
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- A sustainable approach towards solventless organic oxidations catalyzed by polymer immobilized Nb(V)-peroxido compounds with H2O2 as oxidant
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New heterogeneous catalysts comprising of peroxidoniobium(V) complexes immobilized on amino acid grafted cross-linked poly(styrene-divinylbenzene) resin has been developed. Results of FTIR, Raman, NMR, XPS, XRD, EDX, SEM, BET, TGA, and elemental analysis confirmed the successful anchoring of triperoxidoniobium(V), [Nb(O2)3]? species to the host polymer via the pendant amino acid groups. The supported catalysts exhibited excellent performance in epoxidation of styrene and a range of cyclic and terpenic compounds under environmentally acceptable solvent-free condition, with aqueous H2O2 as oxidant. The catalytic protocols provided excellent conversion to the desired epoxide (up to 100%) with selectivity > 99%, TON as high as 1000, and high H2O2 utilization efficiency (92–97%). Moreover, the catalysts efficiently facilitated chemoselective solvent-free oxidation of a variety of thioethers to sulfones at room temperature. Simple operational strategy, easy recyclability for multiple reaction cycles with the consistent activity-selectivity profile are the additional significant attributes of the developed catalytic processes.
- Ahmed, Kabirun,Gogoi, Sandhya Rani,Islam, Nashreen S.,Saikia, Gangutri,Sultana, Sazida Yasmin,Talukdar, Hiya
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- Chiral Imidazo[1,5- a]pyridine-Oxazolines: A Versatile Family of NHC Ligands for the Highly Enantioselective Hydrosilylation of Ketones
-
Herein we report the synthesis and application of a versatile class of N-heterocyclic carbene ligands based on an imidazo[1,5-a]pyridine-3-ylidine backbone that is fused to a chiral oxazoline auxiliary. The key step in the synthesis of these ligands involves the installation of the oxazoline functionality via a microwave-assisted condensation of a cyano-azolium salt with a wide variety of 2-amino alcohols. The resulting chiral bidentate NHC-oxazoline ligands form stable complexes with rhodium(I) that are efficient catalysts for the enantioselective hydrosilylation of structurally diverse ketones. The corresponding secondary alcohols are isolated in good yields (typically >90%) with good to excellent enantioselectivities (80-93% ee). The reported hydrosilylation occurs at ambient temperatures (40 °C), with excellent functional group tolerability. Even ketones bearing heterocyclic substituents (e.g., pyridine or thiophene) or complex organic architectures are hydrosilylated efficiently, which is discussed further in this report.
- Chinna Ayya Swamy,Varenikov, Andrii,Ruiter, Graham De
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supporting information
p. 247 - 257
(2020/02/04)
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- Limonene oxyfunctionalization over Cu-modified silicates employing hydrogen peroxide and t-Butyl hydroperoxide: Reaction pathway analysis
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Limonene oxidation over Cu-nanostructured mesoporous materials was studied. Three solids with different copper content were synthesized employing the template-ion exchange method, and physically-chemically analyzed by a multi-technical characterization. The performance of the molecular sieves as catalysts in the liquid phase oxyfunctionalization of limonene, employing hydrogen peroxide (H2O2) or t-butyl hydroperoxide (TBHP) as oxidants was evaluated. All synthesized Cu-MCM materials were active in the reaction. The obtained results showed that the used oxidant had an important influence on the products distribution under the employed conditions. With H2O2, compounds of high added value such as limonene oxide, carveol and carvone were mainly obtained. Meanwhile, with TBHP, limonene hydroperoxide turned out to be the major product. Finally, a reaction mechanism was proposed for each oxidant.
- Vaschetti, Virginia M.,Cánepa, Analía L.,Barrera, Deicy,Sapag, Karim,Eimer, Griselda A.,Casuscelli, Sandra G.
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- Selective Allylic Oxidation of Terpenic Olefins Using Co-Ag Supported on SiO2 as a Novel, Efficient, and Recyclable Catalyst
-
Co-Ag supported on the SiO2 catalyst was synthesized by the sol-gel method and characterized using XRD, FT-IR, TG-DTG, BET, CV, and SEM/EDX analysis. The catalytic performance of the resulting catalyst was examined by the oxidation of mono and sesquiterpenic olefins using hydrogen peroxide and tert-butyl peroxide as oxidant agents. Various parameters such as catalyst amount, temperature, and solvents have been studied. The Co-Ag supported on the SiO2 catalyst showed a high activity, selectivity, and recyclability for the selected oxidation reaction.
- Aberkouks, Abderrazak,Mekkaoui, Ayoub Abdelkader,Ait Ali, Mustapha,El Firdoussi, Larbi,El Houssame, Soufiane
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-
- Photocontrolled Cobalt Catalysis for Selective Hydroboration of α,β-Unsaturated Ketones
-
Selectivity between 1,2 and 1,4 addition of a nucleophile to an α,β-unsaturated carbonyl compound has classically been modified by the addition of stoichiometric additives to the substrate or reagent to increase their “hard” or “soft” character. Here, we demonstrate a conceptually distinct approach that instead relies on controlling the coordination sphere of a catalyst with visible light. In this way, we bias the reaction down two divergent pathways, giving contrasting products in the catalytic hydroboration of α,β-unsaturated ketones. This includes direct access to previously elusive cyclic enolborates, via 1,4-selective hydroboration, providing a straightforward and stereoselective route to rare syn-aldol products in one-pot. DFT calculations and mechanistic experiments confirm two different mechanisms are operative, underpinning this unusual photocontrolled selectivity switch.
- Beltran, Frédéric,Bergamaschi, Enrico,Funes-Ardoiz, Ignacio,Teskey, Christopher J.
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supporting information
p. 21176 - 21182
(2020/09/17)
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- Engineering a Highly Defective Stable UiO-66 with Tunable Lewis-Br?nsted Acidity: The Role of the Hemilabile Linker
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The stability of metal-organic frameworks (MOFs) typically decreases with an increasing number of defects, limiting the number of defects that can be created and limiting catalytic and other applications. Herein, we use a hemilabile (Hl) linker to create up to a maximum of six defects per cluster in UiO-66. We synthesized hemilabile UiO-66 (Hl-UiO-66) using benzene dicarboxylate (BDC) as linker and 4-sulfonatobenzoate (PSBA) as the hemilabile linker. The PSBA acts not only as a modulator to create defects but also as a coligand that enhances the stability of the resulting defective framework. Furthermore, upon a postsynthetic treatment in H2SO4, the average number of defects increases to the optimum of six missing BDC linkers per cluster (three per formula unit), leaving the Zr-nodes on average sixfold coordinated. Remarkably, the thermal stability of the materials further increases upon this treatment. Periodic density functional theory calculations confirm that the hemilabile ligands strengthen this highly defective structure by several stabilizing interactions. Finally, the catalytic activity of the obtained materials is evaluated in the acid-catalyzed isomerization of α-pinene oxide. This reaction is particularly sensitive to the Br?nsted or Lewis acid sites in the catalyst. In comparison to the pristine UiO-66, which mainly possesses Br?nsted acid sites, the Hl-UiO-66 and the postsynthetically treated Hl-UiO-66 structures exhibited a higher Lewis acidity and an enhanced activity and selectivity. This is further explored by CD3CN spectroscopic sorption experiments. We have shown that by tuning the number of defects in UiO-66 using PSBA as the hemilabile linker, one can achieve highly defective and stable MOFs and easily control the Br?nsted to Lewis acid ratio in the materials and thus their catalytic activity and selectivity.
- De Geyter, Nathalie,De Vos, Dirk E.,Feng, Xiao,Hajek, Julianna,Hoffman, Alexander E. J.,Jena, Himanshu Sekhar,Leus, Karen,Leyssens, Karen,Marquez, Carlos,Meynen, Vera,Morent, Rino,Van Der Voort, Pascal,Van Speybroeck, Veronique,Veerapandian, Savita K. P.,Wang, Guangbo
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p. 3174 - 3183
(2020/03/10)
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- Chemoselective Luche-Type Reduction of α,β-Unsaturated Ketones by Magnesium Catalysis
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The chemoselective reduction of α,β-unsaturated ketones by use of an economic and readily available Mg catalyst has been developed. Excellent yields for a wide range of ketones have been achieved under mild reaction conditions, short times, and low catalyst loadings (0.2-0.5 mol %).
- Jang, Yoon Kyung,Magre, Marc,Rueping, Magnus
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p. 8349 - 8352
(2019/10/16)
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- A Cu-Doped ZIF-8 metal organic framework as a heterogeneous solid catalyst for aerobic oxidation of benzylic hydrocarbons
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Mixed-metal metal organic frameworks have received considerable attention in recent years and it has been shown that the activity of the parent metal organic framework (MOF) is often enhanced upon doping with external metal ions within the framework. In this context, Cu2+ ions with different loadings were incorporated within the ZIF-8 framework to obtain a series of Cu-doped ZIF-8 materials and their activity was examined in the aerobic oxidation of hydrocarbons. The as-synthesized Cu-doped solids were characterized by powder X-ray diffraction (XRD), ultraviolet diffuse reflectance spectroscopy (UV-DRS), scanning electron microscopy (SEM), Fourier Transform infrared (FT-IR), electron paramagnetic resonance (EPR) and inductively coupled plasma (ICP) analysis. The experimental results revealed that the activity of Cu-doped ZIF-8 is much higher than that of the parent ZIF-8 in all the tested substrates at 120 °C. Furthermore, the activity of the Cu-doped ZIF-8 with the highest Cu loading was eight fold higher than that of the parent ZIF-8 in the aerobic oxidation of cyclooctane (1) at 120 °C with more than 80% selectivity to the corresponding cyclooctanol/cyclooctanone (ol/one) mixture. Cu-doped ZIF-8 was reused two times with no significant drop in its activity under identical conditions. Furthermore, comparison of the two times reused solid with that of the fresh solid by powder XRD and SEM analysis revealed identical structural integrity and morphology, respectively during the oxidation reactions.
- Nagarjun, Nagarathinam,Dhakshinamoorthy, Amarajothi
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p. 18702 - 18712
(2019/12/09)
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- Stereodivergent Synthesis of Carveol and Dihydrocarveol through Ketoreductases/Ene-Reductases Catalyzed Asymmetric Reduction
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Chiral carveol and dihydrocarveol are important additives in the flavor industry and building blocks in the synthesis of natural products. Despite the remarkable progress in asymmetric catalysis, convenient access to all possible stereoisomers of carveol and dihydrocarveol remains a challenge. Here, we present the stereodivergent synthesis of carveol and dihydrocarveol through ketoreductases/ene-reductases catalyzed asymmetric reduction. By directly asymmetric reduction of (R)- and (S)-carvone using ketoreductases, which have Prelog or anti-Prelog stereopreference, all four possible stereoisomers of carveol with medium to high diastereomeric excesses (up to >99 %) were first observed. Then four stereoisomers of dihydrocarvone were prepared through ene-reductases catalyzed diastereoselective synthesis. Asymmetric reduction of obtained dihydrocarvone isomers by ketoreductases further provide access to all eight stereoisomeric dihydrocarveol with up to 95 % de values. In addition, the absolute configurations of dihydrocarveol stereoisomers were determined by using modified Mosher's method.
- Guo, Jiyang,Zhang, Rui,Ouyang, Jingping,Zhang, Feiting,Qin, Fengyu,Liu, Guigao,Zhang, Wenhe,Li, Hengyu,Ji, Xiaohong,Jia, Xian,Qin, Bin,You, Song
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p. 5496 - 5504
(2018/11/30)
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- OXIDATION OF LIMONENE
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The invention discloses a process for the oxidation of limonene, comprising the reaction of limonene with hydrogen peroxide in the presence of a catalyst containing atoms and/or ions of at least one metal, selected from the group consisting of molybdenum, tungsten, scandium, vanadium, titanium, lanthanum, zirconium, praseodymium, neodymium, samarium, europium, terbium, dysprosium, erbium or ytterbium, characterised in that the molecular weight of the catalyst is less than 2,000 g/mol and that the reaction is performed at a pH value of more than 7.5.
- -
-
Paragraph 0043; 0045; 0046
(2018/06/15)
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- Photoinduced Carboborative Ring Contraction Enables Regio- and Stereoselective Synthesis of Multiply Substituted Five-Membered Carbocycles and Heterocycles
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We report herein a photoinduced carboborative ring contraction of monounsaturated six-membered carbocycles and heterocycles. The reaction produces substituted five-membered ring systems stereoselectively and on preparative scales. The products feature multiple stereocenters, including contiguous quaternary carbons. We show that the reaction can serve as a synthetic platform for ring system alteration of natural products. The reaction can also be used in natural product synthesis. A concise total synthesis of artalbic acid has been enabled by a sequence of photoinduced carboborative ring contraction, Rauhut-Currier reaction, and nitrilase-catalyzed hydrolysis. The synthetic utility of the reaction has been further demonstrated by converting the intermediate organoboranes to alcohols, amines, and alkenes.
- Jin, Shengfei,Nguyen, Vu T.,Dang, Hang T.,Nguyen, Dat P.,Arman, Hadi D.,Larionov, Oleg V.
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supporting information
p. 11365 - 11368
(2017/08/30)
-
- Hydrogenation of Carbonyl Derivatives with a Well-Defined Rhenium Precatalyst
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The first efficient and general rhenium-catalyzed hydrogenation of carbonyl derivatives was developed. The key to the success of the reaction was the use of a well-defined rhenium complex bearing a tridentate diphosphinoamino ligand as the catalyst (0.5 mol %) at 70 °C in the presence of H2 (30 bar). The mechanism of the reaction was investigated by DFT(PBE0-D3) calculations.
- Wei, Duo,Roisnel, Thierry,Darcel, Christophe,Clot, Eric,Sortais, Jean-Baptiste
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- Preparation method of carvone
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The invention relates to a preparation method of carvone. The carvone is prepared by using easily-obtained alpha-pinene as a raw material and performing three-step reaction of epoxidation- isomerism-oxidization. The epoxidation- isomerism reaction can be carried out continuously; after finishing the epoxidation reaction, ligand, free radical initiator and transition metal additive are added to perform isomerism reaction and generate carvone; furthermore, the carvone is prepared through oxidization reaction. The method is simple in process, easy to obtain pinene raw material; the method avoids the shortcomings of low yield, poor selectivity, difficult separation, and massive hardly-disposed waste water of a traditional process, and is applicable to the industrial production.
- -
-
Paragraph 0025; 0060; 0061; 0065; 0068; 0071; 0074; 0077
(2017/08/31)
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- Synthesis, characterization and catalytic application of a new organometallic oligomer based on polyhedral oligomeric silsesquioxane
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Although homogeneous catalysts provide high performance and selectivity, the difficulty of separation and recycling of these catalysts has bothered the scientific community worldwide. Therefore, the demand for heterogeneous catalysts that possess the advantages of homogeneous ones, with ease of separation and recyclability remains a topic of major impact. The oligomeric catalyst synthesized in this work was characterized using elemental analysis, Fourier transform infrared, 13C NMR, 29Si NMR and energy-dispersive X-ray spectroscopies, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy and Brunauer–Emmett–Teller analysis and compared to its homogeneous counterpart [W(CO)3Br2(ATC)] in the epoxidation of 1-octene, cyclooctene, (S)-limonene, cis-3-hexen-1-ol, trans-3-hexen-1-ol and styrene. The results showed that the percentage conversion for the homogeneous species [W(CO)3Br2(ATC)] was slightly higher than for the oligomeric catalyst (POSS-ATC-[W(CO)3Br2]). Furthermore, the selectivity for epoxide of the oligomeric catalyst was greater than that of the homogeneous catalyst by about 25% when (S)-limonene was used. Great conversions (yields) of products were obtained with a wide range of substrates and the catalyst was recycled many times without any substantial loss of its catalytic activity.
- Vieira, Eduardo Guimar?es,Silva, Rafael Oliveira,Junior, Enes Furlani,Dias Filho, Newton Luiz
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- Synthesis and properties of novel chiral imidazolium-based ionic liquids derived from carvone
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A large series of novel chiral imidazolium ionic liquids were synthesized using the terpenoid carvone as the chiral substrate. Their specific rotations were characterized and their potential use in chiral recognition was demonstrated by studying interactions with racemic Mosher's acid salt.
- Santamarta, Francisco,Vilas, Miguel,Tojo, Emilia,Fall, Yagamare
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p. 31177 - 31180
(2016/04/08)
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- A General CuCl2-Promoted Alkene Aminochlorination Reaction
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A CuCl2-promoted alkene aminochlorination reaction has been developed. A variety of anilides that contain a mono-, di-, or trisubstituted alkenyl moiety readily participated in this reaction to afford structurally diverse vicinal chloroamines. Studies suggest that the process proceeds by a radical-type mechanism and that CuCl2serves as both the oxidant to generate the amidyl radical as well as the chloride source.
- Li, Shu-Qi,Xiong, Peng,Zhu, Lin,Qian, Xiang-Yang,Xu, Hai-Chao
-
supporting information
p. 3449 - 3455
(2016/07/23)
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- Zeolite-Y immobilized Metallo-ligand complexes: A novel heterogenous catalysts for selective oxidation
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Transition metal [M?=?Co(II), Cu(II)] complexes of H2L1 and H2L2 ligands have been prepared as neat and nanohybrid zeolite-Y immobilized complexes. The various analytical tools such as FTIR, ICP-AES, elemental analysis, UV–vis, Brunauer, Emmett and Teller (BET) surface area analysis, Thermal analysis, scanning electron micrographs, Powder XRD, conductivity, magnetic moment, and AAS were employed for the characterization of the prepared catalysts. Among all catalysts, the [Cu(L1)]-Y (heterogeneous) and [Cu(L1)] (homogeneous) have offered high activity and selectivity over oxidation of cyclohexene. Moreover, the [Cu(L1)] and [Cu(L1)]-Y were employed as catalyst over various organic substrates at identical reaction condition. The immobilized catalyst [Cu(L1)]-Y is found to be moderate active over oxidation of cyclohexane (75.2%,), benzene (8.21%), phenol (14.5%), styrene (87.5), benzyl alcohol (21.5%), limonene (11.2%), α-pinene (9.15%), and cyclooctane (76.8%) with high TON values (21942-2054). The mechanistic study using UV–vis and FTIR suggests the participation of active metalperoxo species, which is reinforced by its high catalytic activity over limonene (16.3%) in the absence oxidant.
- Godhani, Dinesh R.,Nakum, Haresh D.,Parmar, Digvijaysinh K.,Mehta, Jignasu P.,Desai, Nisheeth C.
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p. 105 - 116
(2016/09/07)
-
- Chemoselective reduction of α,β-unsaturated carbonyl compounds with UiO-66 materials
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Allylic alcohols, important intermediates in fine chemical industry, are typically obtained through chemoselective hydrogenation of α,β-unsaturated aldehydes. Here we show that UiO-66, a zirconium-based metal-organic framework can be used in the chemoselective hydrogenation of cinnamaldehyde, both under high hydrogen pressure as silver nanoparticle support, and as transfer hydrogenation catalyst in the Meerwein-Ponndorf-Verley (MPV) reduction. A recyclable 10 wt% Ag/UiO-66 catalyst reached complete conversion after 6 h and 50 bar of H2 with 66% selectivity for cinnamyl alcohol in the inert solvent N,N-dimethylacetamide (DMA). Pure UiO-66 as MPV catalyst with isopropanol reached complete conversion with >90% selectivity after 24 h at 120 °C. The substrate scope was extended to citral and carvone, two α,β-unsaturated carbonyl compounds that are harder to reduce selectively. Introduction of a NO2-functional group into the UiO-66 linker to increase the Lewis acidity was clearly beneficial for the conversion of carvone.
- Plessers, Eva,De Vos, Dirk E.,Roeffaers, Maarten B.J.
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p. 136 - 143
(2016/07/06)
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- Metal oxide-triazole hybrids as heterogeneous or reaction-induced self-separating catalysts
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The hybrid metal oxide-triazole materials [MoO3(trz)0.5] (1) and [W2O6(trz)] (2) (trz?=?1,2,4-triazole) have been hydrothermally synthesized and characterized by different techniques (TGA, SEM, 1H and 13C MAS NMR, FT-IR spectroscopy, and structure determination by Rietveld analysis of high resolution synchrotron powder XRD data). Materials 1 and 2 display distinct behaviors when applied as catalysts for oxidation reactions with alcohol, aldehyde, olefin and sulfide substrates, and are more effective with hydrogen peroxide as the oxidant than with tert-butylhydroperoxide. The MoVI hybrid 1 transforms into soluble active species during cis-cyclooctene epoxidation with H2O2. When consumption of H2O2 reaches completion, spontaneous reassembly of the 2-dimensional molybdenum oxide network of 1 takes place and the hybrid precipitates as a microcrystalline solid that can be easily separated and recycled. Reaction-induced self-separation behavior occurs with 1, H2O2 and other substrates such as methyl oleate and methylphenylsulfide. The WVI hybrid 2 behaves differently, preserving its structural features throughout the heterogeneous catalytic process.
- Amarante, Tatiana R.,Neves, Patrícia,Valente, Anabela A.,Paz, Filipe A. Almeida,Pillinger, Martyn,Gon?alves, Isabel S.
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p. 354 - 367
(2016/07/06)
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- Biologically Inspired and Magnetically Recoverable Copper Porphyrinic Catalysts: A Greener Approach for Oxidation of Hydrocarbons with Molecular Oxygen
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An efficient synthetic method for magnetically recoverable hybrid copper porphyrinic nanomaterials is reported. These functionalized magnetic materials prove to be efficient bioinspired oxidation catalysts of olefins and thiols, using molecular oxygen as oxidant, in total absence of reductants and solvents, with the highest TON (turnover number) yet achieved for this reaction (≈200 000). A comparative study between homogeneous and heterogeneous oxidation of cyclohexene is discussed, revealing the heterogeneous system to be the most promising concerning stability and reusability of the catalysts. The full characterization of the magnetic hybrid porphyrinic nanomaterials, by transmission electron microscopy, flame atomic absorption spectrometry, thermogravimetry, N2 sorption, and infrared spectroscopy, is also described.
- Henriques, César A.,Fernandes, Auguste,Rossi, Liane M.,Ribeiro, M. Filipa,Calvete, Mário J. F.,Pereira, Mariette M.
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p. 3359 - 3368
(2016/06/06)
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- TERPENE AND TERPENOID DERIVATIVES CONTAINING VINYL GROUPS FOR THE PREPARATION OF POLYMERS
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The invention relates to a method for producing functionalised monomers, the method comprising: a) providing a starting material selected from terpenes and terpenoids; b) forming a derivative of the starting material by incorporation of a hydroxyl group; c) esterifying the hydroxyl group of the derivative to introduce a moiety containing a vinyl group, so as to produce a functionalised monomer. The functionalised monomer can be polymerised to obtain a bio-derived polymer.
- -
-
Page/Page column 46; 49
(2015/11/10)
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- Comparative anticonvulsant study of epoxycarvone stereoisomers
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Stereoisomers of the monoterpene epoxycarvone (EC), namely (+)-cis-EC, (-)-cis-EC, (+)-Trans-EC, and (-)-Trans-EC, were comparatively evaluated for anticonvulsant activity in specific methodologies. In the pentylenetetrazole (PTZ)-induced anticonvulsant test, all of the stereoisomers (at 300 mg/kg) increased the latency to seizure onset, and afforded 100% protection against the death of the animals. In the maximal electroshock-induced seizures (MES) test, prevention of tonic seizures was also verified for all of the isomers tested. However, the isomeric forms (+) and (-)-Trans-EC showed 25% and 12.5% inhibition of convulsions, respectively. In the pilocarpine-induced seizures test, all stereoisomers demonstrated an anticonvulsant profile, yet the stereoisomers (+) and (-)-Trans-EC (at 300 mg/kg) showed a more pronounced effect. A strychnine-induced anticonvulsant test was performed, and none of the stereoisomers significantly increased the latency to onset of convulsions; the stereoisomers probably do not act in this pathway. However, the stereoisomers (+)-cis-EC and (+)-Trans-EC greatly increased the latency to death of the animals, thus presenting some protection. The four EC stereoisomers show promise for anticonvulsant activity, an effect emphasized in the isomers (+)-cis-EC, (+)-Trans-EC, and (-)-Trans-EC for certain parameters of the tested methodologies. These results serve as support for further research and development of antiepileptic drugs from monoterpenes.
- Salgado, Paula Regina Rodrigues,Da Fonsêca, Diogo Vilar,Braga, Renan Marinho,De Melo, Cynthia Germoglio Farias,Andrade, Luciana Nalone,De Almeida, Reinaldo Nóbrega,De Sousa, Dami?o Pergentino
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p. 19660 - 19673
(2015/12/23)
-
- Eco-friendly stereoselective reduction of α,β-unsaturated carbonyl compounds by Er(OTf)3/NaBH4 in 2-MeTHF
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An operationally simple and environmentally benign catalytic procedure has been developed to selectively reduce different α,β-unsaturated ketones. The corresponding allylic alcohols are obtained with high chemo- and diastereoselectivity using Er(OTf)3 and NaBH4 in 2-MeTHF. This protocol reduces the amount of catalyst and NaBH4 needed, compared to classical procedures and the stages of extraction/purification are carried out in aqueous solutions avoiding the use of toxic solvents. Taking into account that Er(OTf)3 can be considered even less toxic than table salt and the 'greenness' of 2-MeTHF as a solvent, the system Er(OTf)3/2-MeTHF can be proposed as a cheap, efficient, and environmentally sustainable reduction system for the synthesis of allylic alcohols.
- Nardi, Monica,Sindona, Giovanni,Costanzo, Paola,Oliverio, Manuela,Procopio, Antonio
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p. 1132 - 1135
(2015/02/19)
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- Borinic Acid Catalyzed, Regioselective Chloroacylations and Chlorosulfonylations of 2,3-Epoxy Alcohols
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In the presence of a borinic acid derived catalyst, 2,3-epoxy alcohols undergo couplings with acyl and sulfonyl chlorides. This transformation directly generates O-acylated or O-sulfonylated chlorohydrin diols, with significant levels of regioselectivity for both the ring-opening and O-functionalization steps.
- Tanveer, Kashif,Jarrah, Kareem,Taylor, Mark S.
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supporting information
p. 3482 - 3485
(2015/07/28)
-
- Engineering Rieske Non-Heme Iron Oxygenases for the Asymmetric Dihydroxylation of Alkenes
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The asymmetric dihydroxylation of olefins is of special interest due to the facile transformation of the chiral diol products into valuable derivatives. Rieske non-heme iron oxygenases (ROs) represent promising biocatalysts for this reaction as they can be engineered to efficiently catalyze the selective mono- and dihydroxylation of various olefins. The introduction of a single point mutation improved selectivities (≥95 %) and conversions (>99 %) towards selected alkenes. By modifying the size of one active site amino acid side chain, we were able to modulate the regio- and stereoselectivity of these enzymes. For distinct substrates, mutants displayed altered regioselectivities or even favored opposite enantiomers compared to the wild-type ROs, offering a sustainable approach for the oxyfunctionalization of a wide variety of structurally different olefins. Modulation by mutation: Rieske non-heme iron oxygenases can be used as efficient biocatalysts for the selective oxyfunctionalization of various olefins yielding vicinal cis-diols and allylic alcohols. Introduction of a single amino acid substitution in the active sites of two selected oxygenases resulted in variants with improved stereoselectivities and product formations.
- Gally, Christine,Nestl, Bettina M.,Hauer, Bernhard
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supporting information
p. 12952 - 12956
(2015/11/02)
-
- H- and Fe-modified zeolite beta catalysts for preparation of trans-carveol from α-pinene oxide
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The isomerisation of α-pinene oxide has been intensively investigated for selective preparation of campholenic aldehyde, a compound used in the synthesis of fragrances. Selective preparation of another product of α-pinene oxide rearrangement, trans-carveol, still remains a challenging task. Trans-carveol is a highly valuable compound used in perfume bases, food flavour compositions and as an active pharmaceutical substance in chemoprevention of mammary carcinogenesis. In the present work zeolite beta with different SiO2/Al2O3 molar ratios was modified by iron, characterised and tested per se and in the modified form for trans-carveol preparation from α-pinene oxide. The isomerisation reaction was carried out in a polar basic solvent N,N-dimethylacetamide at 140 °C. The activities and selectivities of the catalysts were correlated with their acid properties and with the iron content.
- Stekrova,Kumar,Díaz,M?ki-Arvela,Murzin, D. Yu.
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p. 237 - 245
(2015/02/19)
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- H- and Fe-modified zeolite beta catalysts for preparation of trans-carveol from α-pinene oxide
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The isomerisation of a-pinene oxide has been intensively investigated for selective preparation of campholenic aldehyde, a compound used in the synthesis of fragrances. Selective preparation of another product of α-pinene oxide rearrangement, trans-carveol, still remains a challenging task. Trans-carveol is a highly valuable compound used in perfume bases, food flavour compositions and as an active pharmaceutical substance in chemoprevention of mammary carcinogenesis. In the present work zeolite beta with different SiO2/Al2O3 molar ratios was modified by iron, characterised and tested per se and in the modified form for trans-carveol preparation from a-pinene oxide. The isomerisation reaction was carried out in a polar basic solvent N, N-dimethylacetamide at 140 °C. The activities and selectivities of the catalysts were correlated with their acid properties and with the iron content.
- Stekrova,Kumar,Daz,M?ki-Arvela,Murzin
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p. 237 - 245
(2015/03/14)
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- Continuous flow photooxygenation of monoterpenes
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Photooxygenation of monoterpenes was conducted in two continuous flow reactors. The first, suitable for lab-scale research, had a maximum yield of 99.9%, and the second, focused on industrial applications, showed a daily output that was 270.0-fold higher than that in batch systems. The use of sunlight instead of an LED lamp gave 68.28% conversion.
- Park, Chan Yi,Kim, Young Joon,Lim, Hyo Jin,Park, Jeong Hyeon,Kim, Mi Jin,Seo, Seung Woo,Park, Chan Pil
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p. 4233 - 4237
(2015/02/19)
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- Improved robustness of heterogeneous Fe-non-heme oxidation catalysts: A catalytic and EPR study
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There is currently a rarity in production and in-depth catalytic study of heterogeneous non-heme Fe catalysts. Herein, two heterogeneous catalysts have been synthesized by covalent grafting of non-heme Fe-complexes, DPEIFe IIICl and HFEIFeIIICl, on SiO2. The catalytic performance of the obtained DPEIFeIII@SiO2 and HFEIFe III@SiO2 materials has been systematically studied for catalytic oxidation of cyclohexene. The catalytic data show that the present non-heme Fe catalysts are functional and can achieve higher activity compared to other non-heme Fe reported so far in the literature. Importantly, the heterogeneneous catalysts show a remarkable robustness and improved oxidative stability vs. the homogeneous ones. Studies by UV-vis and EPR reveal a common mechanistic pattern: CH3CN interacts with the Fe-atom promoting the formation of a Low-Spin (S = 1/2) intermediate, in the presence of H 2O2, probably a FeIII-OOH hydroperoxide. The role of radical intermediates was investigated in detail by spin-trapping techniques. Finally, taking into account the nature of oxidation products, a consistent catalytic mechanism, valid for both homogeneous and heterogeneous catalysts, is discussed.
- Bilis,Stathi,Mavrogiorgou,Deligiannakis,Louloudi
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p. 376 - 389
(2014/01/06)
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- Tin-containing hydrotalcite-like compounds as catalysts for the Meerwein-Ponndorf-Verley reaction
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Hydrotalcite-like compounds (HTs) containing Mg/Al or Mg/Al/Sn were prepared and used as precursors to obtain basic catalysts by calcination at 450 C. The catalysts were used in the Meerwein-Ponndorf-Verley (MPV) reaction of benzaldehyde and cyclohexanone in the presence of 2-propanol as hydrogen donor. The mixed oxide obtained by calcining the tin-containing HT was found to be more catalytically active than that obtained from the Mg/Al HT and the pure magnesium oxide. This result can be ascribed to the mechanism of the reaction, which involves acid-base sites on the catalyst surface. The most active catalyst was used in the MPV reactions of other carbonyl compounds including aldehydes and ketones with excellent conversion and selectivity.
- Jiménez-Sanchidrián, César,Ruiz, José Rafael
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p. 367 - 372
(2013/11/19)
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- Substrate flexibility and reaction specificity of tropinone reductase-like short-chain dehydrogenases
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Annotations of protein or gene sequences from large scale sequencing projects are based on protein size, characteristic binding motifs, and conserved catalytic amino acids, but biochemical functions are often uncertain. In the large family of short-chain dehydrogenases/reductases (SDRs), functional predictions often fail. Putative tropinone reductases, named tropinone reductase-like (TRL), are SDRs annotated in many genomes of organisms that do not contain tropane alkaloids. SDRs in vitro often accept several substrates complicating functional assignments. Cochlearia officinalis, a Brassicaceae, contains tropane alkaloids, in contrast to the closely related Arabidopsis thaliana. TRLs from Arabidopsis and the tropinone reductase isolated from Cochlearia (CoTR) were investigated for their catalytic capacity. In contrast to CoTR, none of the Arabidopsis TRLs reduced tropinone in vitro. NAD(H) and NADP(H) preferences were relaxed in two TRLs, and protein homology models revealed flexibility of amino acid residues in the active site allowing binding of both cofactors. TRLs reduced various carbonyl compounds, among them terpene ketones. The reduction was stereospecific for most of TRLs investigated, and the corresponding terpene alcohol oxidation was stereoselective. Carbonyl compounds that were identified to serve as substrates were applied for modeling pharmacophores of each TRL. A database of commercially available compounds was screened using the pharmacophores. Compounds identified as potential substrates were confirmed by turnover in vitro. Thus pharmacophores may contribute to better predictability of biochemical functions of SDR enzymes.
- Reinhardt, Nicole,Fischer, Juliane,Coppi, Ralph,Blum, Elke,Brandt, Wolfgang,Draeger, Birgit
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- Iron(III) chloride-benzotriazole adducts with trigonal bipyramidal geometry: Spectroscopic, structural and catalytic studies
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The reactions of FeCl3 with benzotriazole (btaH), 1-methylbenzotriazole (Mebta), 5,6-dimethylbenzotriazole (5,6Me2btaH) and 5-chlorobenzotriazole (5ClbtaH) were studied in non-polar solvents. The new solid complexes [FeCl3(btaH)2] (1), [FeCl 3(Mebta)2] (2), [FeCl3(5,6Me 2btaH)2] (3) and [FeCl3(5ClbtaH) 2]·2(5ClbtaH) (4) have been isolated. The structures of the complexes have been determined by single-crystal, X-ray crystallography. The structures of 1-4 consist of mononuclear, high-spin 5-coordinate molecules; in addition, the crystal structure of 4 contains two lattice 5ClbtaH molecules per [FeCl3(5ClbtaH)2] unit. The coordinated benzotriazole molecules behave as monodentate ligands with their ligated atom being the nitrogen of the position 3 of the azole ring. The geometry at iron(III) is trigonal bipyramidal with the chlorido ligands occupying the equatorial sites. The crystal structures of the complexes are stabilized by stacking interactions and H bonds (for 1, 3 and 4 only). The new complexes were characterized by elemental analyses, magnetic susceptibilities at room temperature and spectroscopic (IR, far-IR, solid-state electronic UV/VIS/near-IR, 57Fe-Mo?ssbauer, EPR only for complex 4) methods. All data are discussed in terms of the nature of bonding and the known structures. Complexes 1, 2 and 4 have been tested as homogeneous (MeCN) oxidation catalysts in the presence of the "green" H2O2 oxidant; they display moderate to high catalytic activity in the oxidation of several alkenes, cyclohexane and n-hexane, which is described in detail.
- Anastasiadis, Nikolaos C.,Bilis, George,Plakatouras, John C.,Raptopoulou, Catherine P.,Psycharis, Vassilis,Beavers, Christine,Teat, Simon J.,Louloudi, Maria,Perlepes, Spyros P.
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p. 189 - 202
(2013/10/08)
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- Titanocene-promoted stereoselective eliminations on epoxy alcohols derived from R-(-)-carvone
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The reaction of several stereoisomeric epoxy alcohols, obtained from R-(-)-carvone, and their corresponding formates, acetates, and benzoates, promoted by Cp2TiCl has been studied. The different outcomes of the reaction of epoxy derivatives are rationalized in terms of mechanistically biased processes. The radicals emerging from oxirane cleavage provide two types of reaction: dehydroxylation (deoxycarbonylation) and dehydrogenation. The results offer considerable support for the radical elimination theory of hydroxyl, formyloxyl, and acetoxyl groups. The inability of tertiary radicals to be reduced by the Ti(III) complex is demonstrated unequivocally.
- Fernández-Mateos,Herrero Teijón,Rubio González
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p. 1611 - 1616
(2013/02/25)
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- Heteropoly acid catalysts for the synthesis of fragrance compounds from biorenewables: Isomerization of limonene oxide
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The liquid-phase isomerization of limonene oxide was studied in the presence of heteropoly acid catalysts in aprotic solvents in homogeneous and heterogeneous systems. Among the catalysts were bulk and silica-supported tungstophosphoric acid H3PW12O40 and its acidic Cs salt Cs0.5H0.5PW12O40 (CsPW). The reaction gave dihydrocarvone, a valuable fragrance intermediate, as the main product with turnover numbers of up to 8000. The nature of the solvent had a strong effect on reaction rate and selectivity. CsPW (0.1 mol%) was found to be a highly efficient and truly heterogeneous catalyst for this reaction, providing 82% yield of dihydrocarvone in 1,4-dioxane as a solvent under ambient conditions. This simple catalytic method represents economically attractive route to industrially important compounds starting from bio-renewable substrates easily available from essential oils. The Royal Society of Chemistry 2013.
- Costa, Vinicius V.,Da Silva Rocha, Kelly A.,Kozhevnikov, Ivan V.,Kozhevnikova, Elena F.,Gusevskaya, Elena V.
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p. 244 - 250
(2013/04/10)
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- Hot water-promoted SN1 solvolysis reactions of allylic and benzylic alcohols
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During the studies of hydrolysis of epoxides in water, we found that the hydrolysis of (-)-α-pinene oxide at 20 °C gave enantiomerically pure trans-(-)-sobrerol, whereas the same reaction in water heated at reflux unexpectedly gave a racemic mixture of trans- and cis-sobrerol (trans/cis=6:4). We have examined this remarkable difference in detail and found that hot water, whose behavior is quite different compared with room- or high-temperature water, could promote SN1 solvolysis reactions of allylic alcohols and thus caused the racemization of trans-(-)-sobrerol. The effect of reaction temperature, the addition of organic co-solvent, and the concentration of the solute on the rate of the racemization of trans-(-)-sobrerol were further examined to understand the role that hot water played in the reaction. It was proposed that the catalytic effects of hot water are owing to its mild acidic characteristic, thermal activation, high ionizing power, and better solubility of organic reactant. Further investigation showed that the racemization of other chiral allylic/benzylic alcohols could efficiently proceed in hot water.
- Xu, Zhao-Bing,Qu, Jin
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p. 314 - 323
(2013/03/13)
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- Total synthesis of cyrneine A
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Neuritogenic natural products: The tricyclic diterpene cyrneineA featuring a hexatrienal unit was prepared synthetically for the first time by a Heck reaction, a carbene ring expansion, and a reductive carbonylation. The structure of the natural product was assigned by X-ray crystal analysis of a synthetic sample. Copyright
- Elamparuthi, Elangovan,Fellay, Cindy,Neuburger, Markus,Gademann, Karl
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supporting information; experimental part
p. 4071 - 4073
(2012/06/01)
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- Ti-POSS covalently immobilized onto mesoporous silica: A model for active sites in heterogeneous catalytic epoxidation
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A functionalized Ti-containing polyhedral oligomeric silsesquioxane was anchored on the surface of an ordered SBA-15 and a non-ordered amorphous mesoporous silica. The physico-chemical characterization of the textural, thermal and electronic properties of the final anchored materials led to the evaluation of the distribution of Ti-POSS moieties on the silica surface, of the oxidation state and of the coordination geometry of the titanium centres. It was discovered that Ti-POSS are accommodated mainly as dinuclear dimeric species on the external surface of ordered mesoporous silica or in the large mesopores of non-ordered silica supports. Epoxidation tests on unsaturated terpenes (limonene, carveol and α-pinene) with TBHP as oxidant were performed to monitor the activity and accessibility of Ti(IV) sites in the anchored samples and compared with conventional titanocene-grafted Ti/SBA-15 and Ti/SiO 2 systems. The different chemoselectivity recorded over anchored catalysts, with respect to the grafted ones, can be a potential diagnostic tool to shed light on the mechanism or the molecular intermediates occurring at the surface during the oxidation reaction.
- Carniato, Fabio,Bisio, Chiara,Sordelli, Laura,Gavrilova, Elena,Guidotti, Matteo
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experimental part
p. 244 - 251
(2012/04/10)
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- Fine-tuning the local structure and catalytic activity of titanium-amine functionalized silica in oxidation of limonene by aqueous hydrogen peroxide
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Titanium-amine functionalized silica was successfully prepared by a so-called one-pot approach by using 3-aminopropyltrimethoxysilane (APTMS), tetraethoxysilane (TEOS) and titanium(IV) sulfate as precursors. It is demonstrated that the TEOS/APTMS molar ratio in the synthesis of titanium-amine functionalized silica affected the local coordination of titanium and its corresponding positive impact on catalytic activity in oxidation of limonene by aqueous hydrogen peroxide.
- Yuan, Lai Sin,Efendi, Jon,Razali, Nur Syafiqa Hazirah,Nur, Hadi
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experimental part
p. 85 - 88
(2012/06/15)
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- Influence of the Br?nsted and Lewis acid sites on the catalytic activity and selectivity of Fe/MCM-41 system
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The system Fe2O3/MCM-41, with high iron dispersion, was synthesized in order to introduce Lewis acid sites into the MCM-41 structure. Two calcination atmospheres (inert and oxidant) were used to produce iron nanoclusters with different structural properties. Besides, a silylation treatment was realized on both solids with the aim of neutralizing the Br?nsted acidity associated with the MCM-41 silanol groups. The samples were characterized by atomic absorption spectroscopy, X-ray diffraction at low angles, N2 adsorption, temperature-programmed reduction, Fourier transform infrared spectroscopy, nuclear magnetic resonance of 29Si, and M?ssbauer spectroscopy. The influence of the structural changes of the nanoclusters and the effect of the simultaneous presence of Lewis and Br?nsted acid sites were evaluated studying the product distribution from the α-pinene oxide isomerization reaction. It was determined that the Br?nsted acidity of the Fe/MCM-41 system has not the sufficient acid strength to modify the product distribution which is mainly governed by the Lewis sites.
- Fellenz,Bengoa,Marchetti,Gervasini
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scheme or table
p. 187 - 196
(2012/10/08)
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- Air-stable, nitrile-ligated (cyclopentadienone)iron dicarbonyl compounds as transfer reduction and oxidation catalysts
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A series of air-stable, nitrile-ligated (cyclopentadienone)iron dicarbonyl compounds was synthesized and their activities as catalysts in the transfer reduction of acetophenone were explored. While all were active catalysts, the acetonitrile adduct was chosen for further study and was found to be active in the transfer reduction of aldehydes and ketones and in the Oppenauer-type oxidation of secondary alcohols. The acetonitrile catalyst exhibited activities similar to those of an analogous air-sensitive iron hydride, but unlike the iron hydride it was unreactive in carbonyl reductions using hydrogen gas. Copyright
- Plank, Taylor N.,Drake, Jessica L.,Kim, Daniel K.,Funk, Timothy W.
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supporting information; experimental part
p. 597 - 601
(2012/05/04)
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- Acid/vanadium-containing saponite for the conversion of propene into coke: Potential flame-retardant filler for nanocomposite materials
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Vanadium-containing saponite samples were synthesized in a one-pot synthetic procedure with the aim of preparing samples for potential application as fillers for polymeric composites. These vanadium-modified materials were prepared from an acid support by adopting a synthetic strategy that allowed us to introduce isolated structural V species (H/V-SAP). The physicochemical properties of these materials were investigated by XRD analysis and by DR-UV/Vis and FTIR spectroscopy of CO that was adsorbed at 100 K; these data were compared to those of a V-modified saponite material that did not contain any Bronsted acid sites (Na/V-SAP). The surface-acid properties of both samples (together with the fully acidic H-SAP material and the Na-SAP solid) were studied in the catalytic isomerization of α-pinene oxide. The V-containing solids were tested in the oxidative dehydrogenation reaction of propene to evaluate their potential use as flame-retardant fillers for polymer composites. The effect of tuning the presence of Lewis/Bronsted acid sites was carefully studied. The V-containing saponite sample that contained a marked presence of Bronsted acid sites showed the most interesting performance in the oxidative dehydrogenation (ODH) reactions because they produced coke, even at 773 K. The catalytic data presented herein indicate that the H/V-SAP material is potentially active as a flame-retardant filler. In questo lavoro e stato sintetizzata tramite metodologia one-pot una saponite contenente in struttura vanadio, di interesse come additivo per compositi polimerici. La metodologia di sintesi adottata ha permesso di ottenere un solido acido contenente siti di vanadio strutturale isolati (H/V-SAP). Le proprieta chimico-fisiche di tale materiale sono state studiate tramite XRD, DR-UV-Vis e FT-IR di CO adsorbito a 100 K e confrontate con quelle di una V-saponite priva di acidita di Bronsted (Na/V-SAP). Le proprieta acide di entrambi i materiali (e di saponiti acidi H-SAP e sodica Na-SAP) sono state investigate sottoponendo i campioni ad un test catalitico di isomerizzazione dell' ossido di α-pinene. I campioni contenenti vanadio sono stati infine testati come catalizzatori per la reazione di deidrogenazione ossidativa del propene, con l'obiettivo di valutarne i loro potenziale uso come additivi ritardanti di fiamma per compositi polimerici. La saponite contenente vanadio strutturale e caratterizzata da una marcata acidita di Bronsted ha mostrato le migliori prestazioni catalitiche, producendo prodotti carboniosi anche ad alte temperature di esercizio (773 K). I dati catalitici qui mostrati indicano che il campione H/V-SAP e potenzialmente attivo come ritardante di fiamma per compositi polimerici. A hard day's saponite: An acid/vanadium-containing saponite (H/V-SAP) was synthesized and its physicochemical properties were compared to those of a V-modified saponite material that did not contain acid sites. Both samples were tested in the oxidative dehydrogenation (ODH) reaction of propene to study the capability of the samples to form coke species. H/V-SAP was the most interesting catalyst for the production of coke. Copyright
- Ostinelli, Luca,Recchia, Sandro,Bisio, Chiara,Carniato, Fabio,Marchese, Leonardo,Guidotti, Matteo,Psaro, Rinaldo
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p. 2394 - 2402,9
(2020/08/24)
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- Enantioselective synthesis of a key A-ring intermediate for the preparation of 1α,25-dihydroxyvitamin D3
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A novel approach to the key A-ring α, β-unsaturated aldehyde 1, an important intermediate for the preparation of 1α,25-dihydroxyvitamin D3, has been developed. The strategy started from the inexpensive starting material (R)-carvone with an ene reaction serving as the key step toward the potential synthesis of vitamin D3 analogues bearing the modification at the C-2 position.
- Chen, Yan,Ju, Tong
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supporting information; experimental part
p. 86 - 89
(2011/04/12)
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- Dauben-Michno oxidative transposition of allylic cyanohydrins - Enantiomeric switch of (-)-carvone to (+)-carvone
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Allylic cyanohydrins were subjected to Dauben-Michno oxidation at low temperatures to provide β-cyanoenones in good to excellent yields. The potential of this oxidative transposition as a means of an enantiomeric switch of enones containing a latent plane of symmetry was tested by conversion of (-)-carvone to its enantiomer.
- Hudlicky, Jason R.,Werner, Lukas,Semak, Vladislav,Simionescu, Razvan,Hudlicky, Tomas
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scheme or table
p. 535 - 543
(2011/10/03)
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- Selective photosensitized oxidation and its catalytic regulation of monoterpene with molecular oxygen in different reaction media
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The photo-catalytic oxidation of α-pinene, β-pinene and limonene with molecular oxygen sensitized by tetrachlorotetraiodo-fluorescein sodium salt (RB) has been studied in different reaction media under green light irradiation. Simple and efficient photosensitized oxidation equipment was employed successfully to improve the efficiency of the photosensitized reaction. The results indicate that the photosensitized oxidation products can be directly obtained without after-treatment by reductive reagent. Furthermore, it was found that the product distributions are remarkably affected by reaction media, and that N,N-dimethylformamide (DMF) can regulate the selectivity to products. In particular, the good selectivity (85%) to the main product (myrtenal) and the excellent conversion (99%) were obtained in the absence of any other catalysts when DMF was used as reaction solvent in the photosensitized oxidation of β-pinene. Moreover, the possible photosensitized oxidation reaction mechanism in different media was suggested in the present work.
- You, Kuiyi,Yin, Dulin,Mao, Liqiu,Liu, Pingle,Luo, He'An
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experimental part
p. 321 - 325
(2011/10/13)
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- Synthesis, catalytic oxidation and antimicrobial activity of copper(II) Schiff base complex
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A new polymer supported Cu(II) Schiff base complex was synthesized. The solid complex was characterized by Fourier transform infrared spectroscopy (FT-IR), UV-vis diffuse reflectance spectroscopy (DRS), thermogravimetric analysis (TGA) and scanning electron microscope (SEM). Its homogeneous analogue was also prepared. The catalytic performances of the copper complex in oxidation reactions were evaluated for both homogeneous and heterogeneous systems. The copper(II) complex was found to be efficient catalyst for the oxidation of alkenes, alkanes and aromatic alcohols in the presence of hydrogen peroxide as oxidant at room temperature. The catalytic investigation revealed that the solid complex performs better than the homogeneous one as an oxidation catalyst. The solids containing the immobilized complex can be recovered from the reaction medium and reused almost five times, maintaining good catalytic activity. Furthermore, the in vitro toxicity of the ligand and complex was tested against the growth of bacterial species, viz., Staphylococcus aureus and Escherichia coli.
- Islam,Roy, Anupam Singha,Mondal, Paramita,Mubarak, Manir,Mondal, Sanchita,Hossain, Dildar,Banerjee, Satabdi,Santra
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experimental part
p. 106 - 114
(2011/05/12)
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- Chiral building blocks from R-(-)-carvone: N-bromosuccinimidemediated addition-sceletal rearrangement of (-)-cis-carveol
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Synthetically valuable bicyclic blocks 5, 7 and 9 were prepared by the oxidative cleavage of the double bond of 4 with the RuCl3-NaIO4 system and O3.
- Valeev, Ruslan F.,Selezneva, Nataliya K.,Starikova, Zoya A.,Pankrat'ev, Evgenii Yu.,Miftakhov, Mansur S.
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scheme or table
p. 77 - 79
(2010/06/19)
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- New orthogonally functionalized synthetic blocks from R-(-)-carvone
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The intramolecular cyclization of (-)-cis-carveol under iodine treatment afforded (1R,5R,6S)-6-iodomethyl-2,6-dimethyl-7-oxabicyclo[3.2.1]oct-2-ene that was subjected to allyl oxydation with the complex CrO3DMP giving a synthetically valuable building block, (1R,5R,6S)-6-iodomethyl-2,6-dimethyl-7- oxabicyclo[3.2.1]oct-2-ene-4-one. In the latter the double bond was cleaved by ozonization to obtain the expected trioxo derivative, and the subsequent ozonolysis of its enol form provided a multiple functionalized tetrahydrofuran derivative. Pleiades Publishing, Ltd., 2010.
- Valeev,Khasanova,Miftakhov
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experimental part
p. 670 - 673
(2010/10/04)
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- The thermolysis of α-pinene and verbenone epoxides in supercritical solvents
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Thermal transformations of α-pinene and verbenone epoxides were studied in supercritical solvents with complex compositions, including CO 2, lower alcohols (ethanol and isopropanol), and water, over the temperature and pressure ranges 387-575 K and 135-215 atm. The main product from α-pinene epoxide in a supercritical solvent containing water was campholenic aldehyde and pinocamphone; the total content of these products in the reaction mixture was 80%. Suggestions concerning the mechanism of the thermal isomerization of α-pinene epoxide depending on the acidity of supercritical solvents were made. The direction of verbenone epoxide transformations was independent of the presence of water in the mixture. The main identified products were ketoalcohols with para-menthane and camphane frameworks.
- Anikeev,Il'Ina,Volcho,Ermakova,Salakhutdinov
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scheme or table
p. 1112 - 1117
(2011/01/05)
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