- Ligand effects in the stabilization of gold nanoparticles anchored on the surface of graphene: Implications in catalysis
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Gold nanoparticles (Au NPs) functionalized with N-heterocyclic carbene (NHC) ligands immobilized onto graphene are obtained via spontaneous decomposition of well-defined gold-NHC complexes by reduced graphene oxide (rGO) without reducing agents. NHC ligands are responsible for the formation of air-stable, crystalline and small (3.0–4-0 nm) Au NPs homogeneously distributed on the surface of graphene. The catalytic properties of three Au NPs functionalized with different ligands were tested in two benchmark reactions (hydration of alkynes and intramolecular hydroamination of alkynes). The results reveal a pronounced ligand effect on the stability of Au NPs on graphene, by acting as a bridge between them. The Au NPs functionalized with a NHC ligand lacking a polyaromatic group or having a naphthyl tag displayed limited stability and fast deactivation in the first run. On the contrary, the Au NPs functionalized with a NHC ligand containing a pyrenyl handle showed superior catalytic activity and can be recycled at least ten times. The particle size of the Au NPs is preserved after the recycling process indicating a high stability. These results illustrate the use of purposely designed ligands having affinity for both Au NPs and graphene to increase the stability of the hybrid catalyst.
- Ventura-Espinosa, David,Martín, Santiago,García, Hermenegildo,Mata, Jose A.
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Read Online
- The effects of metals and ligands on the oxidation of n-octane using iridium and rhodium “PNP” aminodiphosphine complexes
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Ir and Rh “PNP” complexes with different ligands are utilized for the oxidation of n-octane. Based on the obtained conversion, selectivity, and the characterized recovered catalysts, it is found that the combination of Ir and the studied ligands does not promote the redox mechanism that is known to result in selective formation of oxo and peroxo compounds [desired species for C(1) activation]. Instead, they support a deeper oxidation mechanism, and thus higher selectivity for ketones and acids is obtained. In contrast, these ligands seem to tune the electron density around the Rh (in the Rh-PNP complexes), and thus result in a higher n-octane conversion and improved selectivity for the C(1) activated products, with minimized deeper oxidation, in comparison to Ir-PNP catalysts.
- Naicker, Dunesha,Alapour, Saba,Friedrich, Holger B
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p. 282 - 289
(2020/12/01)
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- Efficient and region-selective conversion of octanes to epoxides under ambient conditions: Performance of tri-copper catalyst, [Cu3I(L)]+1 (L=7-N-Etppz)
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In this paper, is described the conversion of the octane group of hydrocarbons into industrially important epoxides using tri-copper catalyst, [Cu3I(L)]+1 (L=7-N-Etppz). The role of hydrogen peroxide as a sacrificial oxygen donor during catalytic conversion to epoxides has been investigated. The performance of the catalyst has been evaluated in terms of turnover numbers (TON) and turnover frequencies (TOF) reported in this article.
- Krupadam, Reddithota J.,Nagababu, Penumaka,Paul, Perala Sudheer,Reddy, Thatiparthi Byragi
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p. 742 - 745
(2021/09/28)
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- Method for preparing ketone compound from olefin
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The invention belongs to the technical field of organic chemical synthesis, and discloses a method for preparing a ketone compound from olefin by using an iron catalyst. According to the invention, the ligand and the iron salt form an iron catalyst in the on-site reaction, the raw materials in the formula are easy to obtain, and the synthesis is simple. By using the catalyst, olefin can be efficiently converted into ketone compounds, and compared with a palladium catalyst, the price is very low, and the catalyst is suitable for industrial application.
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Paragraph 0035-0037
(2021/08/19)
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- Flexible pincer backbone revisited: CuSNS complexes as efficient catalysts in paraffin oxidation
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New Cu(II) complexes containing a set of tridentate hybrid SNS ligands were synthesised and fully characterised by IR, HRMS, elemental analysis and single-crystal X-ray diffraction. The complexes with the general formula Cu[bis(Rthioethyl)phenylamine]Cl2 (1); [R = methyl (a); ethyl (b); butyl (c); cyclohexyl (d) and t-butyl (e)] exhibited five-coordinate trigonal bipyramidal geometry around each Cu(II) centre in the solid-state with the S-donor atoms occupying the axial positions. However, complex 1b crystallised as a dimer bridged through a cuprate anion denoted as [1b(μ-CuCl4)1b]. Their application as catalysts in the oxidation of n-octane with hydrogen peroxide (H2O2) as an oxidant gave high substrate conversions to C-8 oxygenate products, mainly octanols, after reduction with PPh3. Notably, complex 1d produced the highest yield of 57% in 1 h reaction time at a catalyst concentration of 1 mol%. In general, high turnover numbers (2830–3180) were recorded for the 1/H2O2 catalytic systems with substantially high combined selectivity of 22–27% to 1-octanol and octanoic acid, which are the more desired products of n-octane oxidation resulting from its terminal carbon (C(1)) activation. The high activity of the catalysts is attributed to metal–ligand cooperative catalysis involving CuII-OOH intermediates as the active species modulated by the tridentate SNS ligands. In comparison with related complexes bearing N-donor atoms, the excellent catalytic performance of these series of CuSNS complexes highlights the critical role of the phenylamine N-donor atom.
- Bala, Muhammad D.,Friedrich, Holger B.,Soobramoney, Lynette
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supporting information
(2021/07/16)
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- Oxidation of Alkenes by Water with H2 Liberation
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Oxidation by water with H2 liberation is highly desirable, as it can serve as an environmentally friendly way for the oxidation of organic compounds. Herein, we report the oxidation of alkenes with water as the oxidant by using a catalyst combination of a dearomatized acridine-based PNP-Ru complex and indium(III) triflate. Compared to traditional Wacker-type oxidation, this transformation avoids the use of added chemical oxidants and liberates hydrogen gas as the only byproduct.
- Ben-David, Yehoshoa,Milstein, David,Tang, Shan
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supporting information
p. 5980 - 5984
(2020/04/27)
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- Regioselective Wacker-Type Oxidation of Internal Olefins in tBuOH Using Oxygen as the Sole Oxidant and tBuONO as the Organic Redox Cocatalyst
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A regioselective Wacker-Tsuji oxidation of internal olefins in tBuOH has been developed using oxygen as the terminal oxidant and tert-butyl nitrite as the simple organic redox cocatalyst without the involvement of hazardous cocatalysts or harsh reaction conditions. A series of internal olefins bearing various functional groups can be oxidized to the corresponding substituted ketones in generally good yields with high regioselectivities.
- Huang, Qing,Li, Ya-Wei,Ning, Xiao-Shan,Jiang, Guo-Qing,Zhang, Xiao-Wei,Qu, Jian-Ping,Kang, Yan-Biao
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supporting information
p. 965 - 969
(2020/02/15)
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- Method for producing methyl ketone by catalytic oxidation of olefin by palladium
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The invention discloses a method for generating methyl ketone by catalyzing oxidization of olefin with palladium. The method comprises the following steps: performing a full reaction and a TLC (Thin Layer Chromatography) track reaction in an organic solvent by taking end-position olefin or a nonterminal olefin compound as a raw material, hydrogen peroxide or hydrogen peroxide tertiary butanol as an oxidizing agent, palladium acetate as a catalyst and inorganic acid as a promoter; extracting with ethyl acetate after finishing the reaction, and performing suction filtration, concentration and purification to obtain a corresponding methyl ketone compound. By adopting the method, the palladium acetate is taken as the catalyst, the application of an expensive palladium complex catalyst is avoided; the hydrogen peroxide or the hydrogen peroxide tertiary butanol is taken as the oxidizing agent, a completely-decomposed product is environment-friendly; the inorganic acid is used in a catalytic amount, so that the influences on the environment and equipment are small; treatment difficulty is lowered by using a low-boiling-point organic solvent; the reaction process is environment-friendly, and treatment is easy after reaction; meanwhile, the method is suitable for the end-position olefin or the nonterminal olefin compound, and is wide in application substrate rang; the defect of low applicability of the conventional Wacker oxidizing reaction is overcome.
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Paragraph 0040; 0041
(2020/09/20)
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- Application of new Ru (II) pyridine-based complexes in the partial oxidation of n-octane
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Tridentate and bidentate Ru (II) complexes were prepared through reaction of four pyridine-based ligands: pyCH2N(R)CH2py {R = propyl, tert-butyl, cyclohexyl and phenyl; py = pyridine} with the [(η6-C6H6)Ru(μ-Cl)Cl]2 dimer. Crystal structures of the new terdentate Ru (II) complexes [Ru{pyCH2N(R)CH2py}C6H6](PF6)2 (R = C3H7 (1), C (CH3)3 (2), C6H11 (3) and the bidentate Ru (II) complex [Ru{pyCH2N(R)}C6H6]PF6 (R = C6H5 (4)) are reported. It was found that complexes 1, 2, 3 and 4 crystallised as mono-metallic species, with a piano stool geometry around each Ru centre. All complexes were active in the selective oxidation of n-octane using t-BuOOH and H2O2 as oxidants. Complexes 2 and 4 reached a product yield of 12% with t-BuOOH as oxidant, however, superior yields (23–32%) were achieved using H2O2 over all systems. The selectivity was predominantly towards alcohols (particularly 2-octanol) over all complexes using t-BuOOH and H2O2 after reduction of the formed alkylhydroperoxides in solution by PPh3. High TONs of up to 2400 were achieved over the Ru/H2O2 systems.
- Chanerika, Revana,Friedrich, Holger B.,Shozi, Mzamo L.
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- Synthesis of Co(II) NNN-pyridine based complexes and their activity in the partial oxidation of n-octane
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A series of four NNN-pyridine based ligands of the general form: pyCH2N(R)CH2py {R = propyl, tert-butyl, cyclohexyl and phenyl; py = pyridine} were synthesised and characterised. Complexation of each ligand to CoCl2?6H2O afforded new Co(II) complexes [Co{pyCH2N(R)CH2py}Cl2] (R = C3H7 (1), C(CH3)3 (2), C6H11 (3) and C6H5 (4)). Single crystal X-ray diffraction data confirmed that complex 1 crystallised as a mononuclear unit and was characterised by a distorted trigonal bipyramidal arrangement of ligands around Co. As catalysts in the oxidation of n-octane using t-BuOOH as oxidant, 2 (10% product yield) was found to be most efficient and the selectivity over 1–4 was predominantly towards 2-octanol, after reduction of alkylhydroperoxides by PPh3. All catalysts were significantly more active in the activation of n-octane using hydrogen peroxide, with a yield of 45% observed over catalyst 3. Furthermore, with H2O2, all catalysts produced a high concentration of alkylhydroperoxides, with catalyst 4 giving up to 91% alcohols after workup. TONs of up to 1100 were achieved over the Co/H2O2 systems.
- Chanerika, Revana,Friedrich, Holger B.,Shozi, Mzamo L.
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- Iron(III)-Catalyzed Hydration of Unactivated Internal Alkynes in Weak Acidic Medium, under Lewis Acid-Assisted Br?nsted Acid Catalysis
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Alkylarylalkynes are converted with full regioselectivity into the corresponding arylketones by formal hydration of the triple bond under weak acidic conditions, at times and temperatures (≤95 °C) comparable to those used for terminal alkynes. The process catalyzed by Fe2(SO4)3nH2O in glacial acetic acid exhibits good functional group compatibility, including that with bulky triple bond substituents, and can be extended to the one-pot transformation of aryltrimethylsilylacetylenes into acetyl derivatives via a desilylation-hydration sequence. The overall reactivity pattern along with proton affinity data indicate that the triple bond is activated by proton transfer rather than by π-interaction with the metal ion. This mechanistic feature, at variance with that of noble metal catalysts, accounts for the total regioselectivity and the insensitivity to steric hindrance exhibited by the Fe2(SO4)3nH2O/AcOH catalytic system. (Figure presented.).
- Antenucci, Achille,Flamini, Piergiorgio,Fornaiolo, Marco Valerio,Di Silvio, Sergio,Mazzetti, Sara,Mencarelli, Paolo,Salvio, Riccardo,Bassetti, Mauro
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p. 4517 - 4526
(2019/08/26)
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- Symmetric triazolylidene Ni(II) complexes applied as oxidation catalysts
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A set of related Ni(II) complexes of N-heterocyclic carbene ligands (NHC) [trans-X2Ni(NHC)2] (X = Cl, I) bearing linear straight chain alkyl wingtip substituents have been synthesised and fully characterised. Single crystal XRD data revealed symmetrically aligned Ni(II) centres within square planar coordination of trans halide, trans NHC ligands. The complexes were used for the catalytic oxidation of alkanes under mild conditions in conjunction with tert-butyl hydroperoxide as an oxidant. Under optimised reaction conditions, the catalytic results pointed to good activities of circa 15% and 19% for cyclohexane and n-octane respectively. Furthermore, the catalytic systems are shown to be very efficient for the oxidation of linear alcohols to corresponding ketones.
- Mncube, Siyabonga G.,Bala, Muhammad D.
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p. 467 - 473
(2018/11/06)
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- Synergistic hydrogen atom transfer with the active role of solvent: Preferred one-step aerobic oxidation of cyclohexane to adipic acid by N-hydroxyphthalimide
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In this work, we developed an one-step aerobic oxidation of cyclohexane to prepare adipic acid, catalyzed by N-hydroxyphthalimide (NHPI) under promoter- and metal-free conditions. A significant beneficial solvent effect for synergistic reaction is observed with varying polarity and hydrogen-bonding strength: detailed study reveals that the solvent environments manipulate catalytic activity and adipic acid selectivity. Cyclic voltammetry measurements and UV–visible spectra of the NHPI catalyst are examined in various solvent environments to understand the active role of solvent in influencing the catalytic-site structure (>NOH) of the molecule. Analysis of the UV–visible spectra reveals that these differences can be rationalized by considering hydrogen-bonding with solvent molecules, which modifies the catalytic-site structure. This observation is in agreement with cyclic voltammetry results: the different reversibility of the catalytic-site (>NOH/>NO[rad]) wave shows that the catalytic activity of NHPI is related to the formation of hydrogen bonds with the active participation of solvents. Computational studies presented herein have furnished mechanistic insights into the effect of solvent environments. Specifically, we present the structures, dissociation energies, and reaction barriers from DFT studies of the reactants and reaction intermediates involved in the two types of H-abstraction on >NO[rad] catalytic-sites for the rate-determining step. The results of modeling the solvent effects using the PCM continuum solvent method predict that the resulting reaction barrier of the rate-controlling H-abstraction for cyclohexane and cyclohexanone is modified significantly: the transition state barrier of H-abstraction for cyclohexane decreases from 22.36 (in benzene) to 20.78 kcal?mol?1 (in acetonitrile); the α-H-abstraction barrier for cyclohexanone decreases from 21.45 to 20.53 kcal?mol?1. The active participation of solvent molecule results in a strong interaction between pre-reaction complex (PINO???H???C NO[rad] catalytic-sites at the transition state. The lower calculated barriers of H-abstraction for cyclohexanone oxidation approximate more closely the experimental results of the higher adipic acid selectivity. Our work provides a dimension of sustainable chemistry for the metal-free preparation of adipic acid: a conversion of 27% with 79% adipic acid selectivity is achieved over use of NHPI catalysts in CH3CN solvent.
- Liang, Futong,Zhong, Wenzhou,Xiang, Liping,Mao, Liqiu,Xu, Qiong,Kirk, Steven Robert,Yin, Dulin
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p. 256 - 269
(2019/09/30)
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- Evaluation of the Catalytic Capability of cis- and trans-Diquinoxaline Spanned Cavitands
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Three new cis-diquinoxaline spanned cavitands were successfully synthesized. These cis-diphosphinated derivatives were applied in homogeneous gold-catalyzed dimerization and hydration of alkynes as well as rhodium-catalyzed styrene hydroformylation. The results were ranked with those obtained with their trans-diphosphinated isomeric analogues. The structure-activity relationship employing these two cavitands reveals that the cis- or trans-positioning of the catalyst centers directly influences cooperation between the two metallic atoms to control catalytic activity, reaction profile, and product selectivity. This comparative study provides us an intellectual basis for future catalytic cavitand chemistry and homogeneous catalysis.
- Inoue, Mami,Kamiguchi, Shinsuke,Ugawa, Katto,Hkiri, Shaima,Bouffard, Jules,Sémeril, David,Iwasawa, Tetsuo
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p. 6261 - 6268
(2019/11/05)
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- Flexible SNS pincer complexes of copper: Synthesis, structural characterisation and application in n-octane oxidation
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Two new tridentate SNS ligands based on a flexible, straight chain amine backbone were prepared and in combination with three related but previously reported ligands were reacted with CuCl2 to yield new tridentate pincer-type copper(II) complexes. The molecular structures of the new ligands bis(cyclohexylthioethyl)methylamine (L1d), bis(t-butylthioethyl)methylamine (L1e), and all the complexes Cu[bis(Rthioethyl)methylamine]Cl2 (1) where R = methyl (a); ethyl (b); butyl (c); cyclohexyl (d) and t-butyl (e); were confirmed by a range of spectroscopic and analytical techniques. Single crystal X-ray diffraction analysis determined the solid-state structures of the salt of L1e and the complexes. Complexes 1a-e all exhibited five-coordinate ligand geometry around each Cu(II) centre defined by the tridentate SNS and two chlorido donors. The complexes were applied as catalysts in the oxidation of n-octane using t-butyl hydroperoxide and hydrogen peroxide (H2O2) as oxidants. The H2O2 based systems yielded up to 36% conversion of n-octane to C-8 oxygenates with very high alcohol selectivity of up to 78%.
- Soobramoney, Lynette,Bala, Muhammad D.,Friedrich, Holger B.,Pillay, Michael N.
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- Utilisation of new NiSNS pincer complexes in paraffin oxidation
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Two series of closely related SNS pincer ligands (L) were synthesised with the major structural variation on the nitrogen backbone containing either the methyl [L = (RSCH2CH2)2NMe: where R = Me (1), Et (2), Bu (3)] or the phenyl [L = (RSCH2CH2)2NPh: where R = Me (4), Et (5), Cy (6)] functional group. When ligands 1–3 were complexed to Ni by reaction with Ni(DME)Cl2 (DME = dimethoxyethane), they respectively yielded three new cationic dimeric [LNi(μ-Cl)3NiL]+ complexes (7–9), whilst ligands 4–6 on reaction with Ni(PPh3)2Br2 respectively yielded neutral mononuclear (LNiBr2) complexes 10–12. All the new compounds were characterised by IR, HRMS, elemental analysis and in addition, single crystal X-ray diffraction for complexes 9–12. X-ray structural data of 9 revealed an unusual three chlorido-bridged Ni dimer with the SNS ligand coordinated in a facial binding mode to the two pseudo-octahedral Ni centres. Molecular structures of complexes 10, 11 and 12 each displayed five-coordinate distorted trigonal bipyramidal geometry around the nickel(II) metal centres. When utilised as catalysts in the tert-butyl hydroperoxide oxidation of n-octane, all the complexes showed activity to mainly products of internal carbon activation (octanones and secondary octanols) with 11 as the most active (10% total substrate to oxygenates yield), whereas 10 was the least active, but most selective towards alcohols (alcohol/ketone = 2.13).
- Soobramoney, Lynette,Bala, Muhammad D.,Friedrich, Holger B.
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- Bispentiptycenyl-N-Heterocyclic Carbene (NHC) Gold Complexes: Highly Active Catalysts for the Room Temperature Hydration of Alkynes
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The virtually quantitative, room temperature hydration of various terminal and internal alkynes in methanol/water requires between 0.01–0.05 molpercent of [AuCl(NHC)] activated with 1.5 equiv. of silver triflate and 45 equiv. of triflic acid (both relative to gold complex) with ton of up to 300.000. Iptycenyl-substituted NHC ligands play the key role and the most efficient NHC ligand is characterized by a hemispherical shape formed by two N-pentiptycenyl substituents. (Figure presented.).
- Bergmann, Marvin,Heidrich, Maximillian,Müller-Borges, Dorian,Plenio, Herbert
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p. 3572 - 3578
(2018/09/22)
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- Rational Design of a Metallocatalytic Cavitand for Regioselective Hydration of Specific Alkynes
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The synthesis of a functionalized supramolecular cavitand with inwardly oriented AuI and P=O moieties was explored, including its catalytic proclivity in the selective hydration of internal alkynes. The cavitand works as a supramolecular flask device: AuI coordinates to the triple bond, the P=O moiety connects with a H2O molecule, and the cavity favors folding of a single alkynyl side chain. Several tests of different substrate patterns indicated that the cavity was substrate specific, similar to enzymatic catalysis.
- Endo, Naoki,Inoue, Mami,Iwasawa, Tetsuo
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supporting information
p. 1136 - 1140
(2018/03/13)
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- Selective Catalytic Hydration of Alkynes in the Presence of Au-Cavitands: A Study in Structure–Activity Relationships
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The effects of the catalytic cavities in gold-functionalized cavitands in the hydration of internal alkynes have been studied. Variations on cavitand structures revealed the importance of two features that were studied: (1) flanking aromatic rings, and (2) an adjacent P=O moiety. The di-quinoxaline-spanned resorcin[4]arene system provides a well-defined compartment, in which a cationic Au ion activates an internal alkyne for conversion into a ketone by delivery of water that has also been activated, this time by a P=O moiety. We synthesized four variations on our parent cavitand. Variations of the cavitand walls include replacement of quinoxaline components with pyrazine or methylene units. Variation of the P=O center was accomplished with methylene or quinoxaline moieties. All variants displayed lower catalytic activity or selectivity, allowing us to confirm the significance both of an internal cavity and of an activation site for water.
- Inoue, Mami,Ugawa, Katto,Maruyama, Tomoyuki,Iwasawa, Tetsuo
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p. 5304 - 5311
(2018/09/12)
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- Biocatalytic Racemization Employing TeSADH: Substrate Scope and Organic Solvent Compatibility for Dynamic Kinetic Resolution
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Racemization in combination with a kinetic resolution is the base for a dynamic kinetic resolution (DKR). Biocatalytic racemization was successfully performed for a broad scope of sec-alcohols by employing a single alcohol dehydrogenase (ADH) variant from Thermoanaerobacter pseudoethanolicus (formerly T. ethanolicus; TeSADH W110A I86A C295A). The catalyst employed as a lyophilized whole cell preparation or cell free extract, which tolerated various non-water miscible organic solvents under micro-aqueous or two-phase conditions, whereby cyclohexane and n-hexane suited best. Various concepts for combining the enzymatic racemization with an enzymatic kinetic resolution to achieve overall a bis-enzymatic DKR were evaluated. A proof of concept showed a successful DKR with racemization in aqueous phase combined with acylation in the organic phase.
- Pop?oński, Jaros?aw,Reiter, Tamara,Kroutil, Wolfgang
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p. 763 - 768
(2018/02/27)
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- Base metal Schiff base complexes applied as catalysts for the oxidation of n-octane
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The catalytic oxidation of n-octane to value-added oxygenates has been studied with a series of salen-type complexes of iron. The four iron Schiff base complexes N,N′-bis(salicylidene)-L-iron(III) chloride [L?=?1,2-phenylenediamine (5); ethylenediamine (6); propylenediamine (7) and butylenediamine (8)] were synthesised by variation of the bridging diamine backbone. All the complexes are fully characterised and the crystal structure of 7 is for the first time reported as a centrosymmetric dimer observed to crystallise in the triclinic P1 ̄ system. The application of 5–8 in this oxidation reaction represents a rare example of the systematic use of iron-salen complexes for the liquid-phase functionalisation of Csp3–H bonds of straight chain alkanes. All catalysts displayed activity with H2O2 and TBHP as oxidants that resulted in a mixture of oxygenated products dominated by the ketones (2-, 3- and 4-octanones). Observed trends and variations in catalytic activities of the complexes is related to differences in chemical/structural features and changes in reaction conditions. A detailed analysis of selectivity parameters of the complexes to the variety of oxygenates is also presented and rationalised.
- Kadwa, Ebrahim,Friedrich, Holger B.,Bala, Muhammad D.
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p. 112 - 117
(2017/04/27)
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- Alkane oxidation catalysed by a self-folded multi-iron complex
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A preorganised ligand scaffold is capable of coordinating multiple Fe(II) centres to form an electrophilic CH oxidation catalyst. This catalyst oxidises unactivated hydrocarbons including simple, linear alkanes under mild conditions in good yields with selectivity for the oxidation of secondary CH bonds. Control complexes containing a single metal centre are incapable of oxidising unstrained linear hydrocarbons, indicating that participation of multiple centres aids the CH oxidation of challenging substrates.
- Mettry, Magi,Moehlig, Melissa Padilla,Gill, Adam D.,Hooley, Richard J.
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p. 120 - 128
(2016/11/09)
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- Oxidation of Alkanes by Periodate Using a MnV Nitrido Complex as Catalyst
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The design of catalytic systems that can selectively oxidize unactivated C?H bonds under mild conditions is a challenge to chemists. We report here that the manganese(V) nitrido complex [MnV(N)(CN)4]2? is a highly efficient catalyst for the oxidation of alkanes by periodate (IO4 ?) at ambient conditions. Excellent yields of alcohols and ketones (>95 %) are obtained with a maximum turnover number (TON) of 3000.
- Ma, Li,Chen, Lingjing,Lau, Tai-Chu
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p. 2846 - 2848
(2016/10/25)
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- Ligand Effects in the Gold Catalyzed Hydration of Alkynes
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In the gold(I) (e. g. L-Au-OTf) catalyzed hydration of alkynes, the steric hindrance of ligands has a significant influence on the kinetics of the reaction, whereas their electronic effects are less influential. Very low loadings (ppm levels) of a gold catalyst containing a highly sterically hindered phosphine ligand (e. g. L4-Au-OTf) (L4=Me3(OMe)tBuXPhos) is able to catalyze the hydration of a wide range of alkyne substrates in good yields, at relatively low temperature.
- Ebule, Rene E.,Malhotra, Deepika,Hammond, Gerald B.,Xu, Bo
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supporting information
p. 1478 - 1481
(2016/05/19)
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- Acidic Co-Catalysts in Cationic Gold Catalysis
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A systematic study on the effects of Lewis or Br?nsted acid co-catalysts in gold-catalyzed reactions was undertaken using representative reactions (O-, N-, and C-nucleophilic additions to alkynes). Through these reactions, it was demonstrated that an acidic co-catalyst can increase the catalyst turnover significantly, enabling practical reaction rates at competitive catalyst loadings (1 mol %). Further investigation is currently underway to improve the understanding of the subtle principles underlying these experimental observations.
- Barrio, Pablo,Kumar, Manish,Lu, Zhichao,Han, Junbin,Xu, Bo,Hammond, Gerald B.
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supporting information
p. 16410 - 16414
(2016/11/09)
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- Supported rhenium nanoparticle catalysts for acceptorless dehydrogenation of alcohols: Structure-activity relationship and mechanistic studies
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Al2O3-supported Re with different oxidation states and Re0 metal nanoparticles on various supports are prepared, characterized and tested for the dehydrogenation of 2-octanol. The activity of Re/Al2O3 increases with the fraction of metallic Re. The activity of metallic Re depends on the support oxides, and the support with moderate electronegativity (Al2O3) gives the highest turnover frequency (TOF) per surface Re0 site. Re/Al2O3 is effective for acceptorless dehydrogenation of various aliphatic secondary alcohols to ketones. The kinetic isotope effects on the dehydrogenation of 2-propanol show that dissociation of the α-C-H bond of 2-propanol is the rate-limiting step. The IR study of the reaction of gas phase 2-propanol over the Re/Al2O3 surface shows that the acid-base pair site of Al2O3 is responsible for the O-H dissociation of 2-propanol. The structural requirements are discussed on the basis of the mechanistic results.
- Kon, Kenichi,Onodera, Wataru,Toyao, Takashi,Shimizu, Ken-Ichi
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p. 5864 - 5870
(2016/08/05)
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- Selective Oxidation of Aliphatic Alcohols using Molecular Oxygen at Ambient Temperature: Mixed-Valence Vanadium Oxide Photocatalysts
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Here we report a class of photocatalysts: mixed-valence vanadium oxide particles grafted onto a variety of oxide supports. In these catalysts V6O13 species with mixed oxidation states (V4+ or V5+) are believed to be catalytically active sites. These catalysts successfully enable alcohol oxidation to selectively produce aldehydes and ketones using O2 as the oxidant. The catalytic process is driven by visible light irradiation at room temperature and, most importantly, progresses with negligible overoxidation. The catalysts can even selectively oxidize aliphatic alcohols, which are much more challenging to control in comparison to aromatic analogues. They can also be applied to the activation and oxidation of the otherwise stable C-H bonds of saturated aromatic hydrocarbons, such as toluene and xylene, under irradiation. Both experimental results and density functional theory (DFT) simulations suggest the formation of V6O13-alkoxide species as the initial step in the catalytic cycle. The V6O13-alkoxide then acts as the light harvester, being excited by light of wavelength shorter than 550 nm. Facile room-temperature C-H bond cleavage in the excited state V6O13-alkoxide in the presence of O2 leads to the carbonyl-containing products. These findings demonstrate an example of light-driven selective oxidation of diverse alcohols via in situ formation of photoresponsive V6O13-alkoxide species. This catalytic process is especially valuable for the synthesis of temperature-sensitive products and represents an alternative pathway to many conventional thermal oxidation reactions.
- Zavahir, Sifani,Xiao, Qi,Sarina, Sarina,Zhao, Jian,Bottle, Steven,Wellard, Mark,Jia, Jianfeng,Jing, Liqiang,Huang, Yiming,Blinco, James P.,Wu, Haishun,Zhu, Huai-Yong
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p. 3580 - 3588
(2016/07/06)
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- Cytochrome P450 oxygenases
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Nucleic acids encoding cytochrome P450 variants are provided. The cytochrome P450 variants of have a higher alkane-oxidation capability, alkene-oxidation capability, and/or a higher organic-solvent resistance than the corresponding wild-type or parent cytochrome P450 enzyme. A preferred wild-type cytochrome P450 is cytochrome P450 BM-3. Preferred cytochrome P450 variants include those having an improved capability to hydroxylate alkanes and epoxidate alkenes comprising less than 8 carbons, and have amino acid substitutions corresponding to V78A, H236Q, and E252G of cytochrome P450 BM-3. Preferred cytochrome P450 variants also include those having an improved hydroxylation activity in solutions comprising co-solvents such as DMSO and THF, and have amino acid substitutions corresponding to T235A, R471A, E494K, and S1024E of cytochrome P450 BM-3.
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Page/Page column 25; 26
(2016/05/24)
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- From DNA to catalysis: A thymine-acetate ligated non-heme iron(III) catalyst for oxidative activation of aliphatic C-H bonds
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A non-heme, iron(iii)/THA(thymine-1-acetate) catalyst together with H2O2 as an oxidant is efficient in oxidative C-H activation of alkanes. Although having a higher preference for tertiary C-H bonds, the catalyst also oxidizes aliphatic secondary C-H bonds into carbonyl compounds with good to excellent conversions. Based on the site selectivity of the catalyst and our mechanistic studies the reaction proceeds via an Fe-oxo species without long lived carbon centered radicals.
- Al-Hunaiti, Afnan,R?is?nen, Minn?,Repo, Timo
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p. 2043 - 2046
(2016/02/05)
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- Novel cage-like hexanuclear nickel(II) silsesquioxane. Synthesis, structure, and catalytic activity in oxidations with peroxides
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New hexanuclear nickel(II) silsesquioxane [(PhSiO1.5)12(NiO)6(NaCl)] (1) was synthesized as its dioxane-benzonitrile-water complex (PhSiO1,5)12(NiO)6(NaCl)(C4H8O2)13(PhCN)2(H2O)2 and studied by X-ray and topological analysis. The compound exhibits cylinder-like type of molecular architecture and represents very rare case of polyhedral complexation of metallasilsesquioxane with benzonitrile. Complex 1 exhibited catalytic activity in activation of such small molecules as light alkanes and alcohols. Namely, oxidation of alcohols with tert-butylhydroperoxide and alkanes with meta-chloroperoxybenzoic acid. The oxidation of methylcyclohexane gave rise to the isomeric ketones and unusual distribution of alcohol isomers.
- Bilyachenko, Alexey N.,Yalymov, Alexey I.,Shul'pina, Lidia S.,Mandelli, Dalmo,Korlyukov, Alexander A.,Vologzhanina, Anna V.,Es'kova, Marina A.,Shubina, Elena S.,Levitsky, Mikhail M.,Shul'pin, Georgiy B.
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- Non-redox metal ions can promote Wacker-type oxidations even better than copper(II): A new opportunity in catalyst design
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In Wacker oxidation and inspired Pd(ii)/Cu(ii)-catalyzed C-H activations, copper(ii) is believed to serve in re-oxidizing of Pd(0) in the catalytic cycle. Herein we report that non-redox metal ions like Sc(iii) can promote Wacker-type oxidations even better than Cu(ii); both Sc(iii) and Cu(ii) can greatly promote Pd(ii)-catalyzed olefin isomerization in which the redox properties of Cu(ii) are not essential, indicating that the Lewis acid properties of Cu(ii) can play a significant role in Pd(ii)-catalyzed C-H activations in addition to its redox properties. Characterization of catalysts using UV-Vis and NMR indicated that adding Sc(OTf)3 to the acetonitrile solution of Pd(OAc)2 generates a new Pd(ii)/Sc(iii) bimetallic complex having a diacetate bridge which serves as the key active species for Wacker-type oxidation and olefin isomerization. Linkage of trivalent Sc(iii) to the Pd(ii) species makes it more electron-deficient, thus facilitating the coordination of olefin to the Pd(ii) cation. Due to the improved electron transfer from olefin to the Pd(ii) cation, it benefits the nucleophilic attack of water on the olefinic double bond, leading to efficient olefin oxidation. The presence of excess Sc(iii) prevents the palladium(0) black formation, which has been rationalized by the formation of the Sc(iii)...H-Pd(ii) intermediate. This intermediate inhibits the reductive elimination of the H-Pd(ii) bond, and facilitates the oxygen insertion to form the HOO-Pd(ii) intermediate, and thus avoids the formation of the inactive palladium(0) black. The Lewis acid promoted Wacker-type oxidation and olefin isomerization demonstrated here may open up a new opportunity in catalyst design for versatile C-H activations.
- Qin, Shuhao,Dong, Lei,Chen, Zhuqi,Zhang, Sicheng,Yin, Guochuan
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p. 17508 - 17515
(2015/10/19)
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- Efficient hydration of alkynes through acid-assisted Bronsted acid catalysis
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The combined acid catalyzed hydration of alkynes is an efficient one-step synthesis of carbonyl compounds. This atom-economical method is effective with a wide range of substrates, and the products are obtained in very good yields with low catalyst loading (0.2%). Furthermore, solid acids like Nafion were also efficient and could be easily recycled multiple times without loss of reactivity.
- Liang, Shengzong,Hammond, Gerald B.,Xu, Bo
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supporting information
p. 903 - 906
(2015/01/09)
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- Catalytic transformation of aliphatic alcohols to corresponding esters in o2 under neutral conditions using visible-light irradiation
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Selective oxidation of aliphatic alcohols under mild and base-free conditions is a challenging process for organic synthesis. Herein, we report a one-pot process for the direct oxidative esterification of aliphatic alcohols that is significantly enhanced by visible-light irradiation at ambient temperatures. The new methodology uses heterogenerous photocatalysts of gold-palladium alloy nanoparticles on a phosphate-modified hydrotalcite support and molecular oxygen as a benign oxidant. The alloy photocatalysts can absorb incident light, and the light-excited metal electrons on the surface of metal nanoparticles can activate the adsorbed reactant molecules. Tuning the light intensity and wavelength of the irradiation can remarkably change the reaction activity. Shorter wavelength light (550 nm) drives the reaction more efficiently than light of longer wavelength (e.g., 620 nm), especially at low temperatures. The phosphate-exchanged hydrotalcite support provides sufficient basicity (and buffer) for the catalytic reactions; thus, the addition of base is not required. The photocatalysts are efficient and readily recyclable. The findings reveal the first example of using "green" oxidants and light energy to drive direct oxidative esterification of aliphatic alcohols under base-free, mild conditions.
- Xiao, Qi,Liu, Zhe,Bo, Arixin,Zavahir, Sifani,Sarina, Sarina,Bottle, Steven,Riches, James D.,Zhu, Huaiyong
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p. 1956 - 1966
(2015/03/04)
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- Regioselective Isomerization of 2,3-Disubstituted Epoxides to Ketones: An Alternative to the Wacker Oxidation of Internal Alkenes
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We report an alternative pathway to the Wacker oxidation of internal olefins involving epoxidation of trans-alkenes followed by a mild and highly regioselective isomerization to give the major ketone isomers in 66-98% yield. Preliminary kinetics and isotope labeling studies suggest epoxide ring opening as the turnover limiting step in our proposed mechanism. A similar catalytic system was applied to the kinetic resolution of select trans-epoxides to give synthetically useful selectivity factors of 17-23 for benzyl-substituted substrates.
- Lamb, Jessica R.,Mulzer, Michael,Lapointe, Anne M.,Coates, Geoffrey W.
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supporting information
p. 15049 - 15054
(2015/12/08)
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- Co-oxidation of octane and benzaldehyde using molecular oxygen with Au-Pd/carbon prepared by sol-immobilisation
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The selective oxidation of linear alkanes with molecular oxygen under mild conditions remains a challenging topic in the field of catalysis. In this study we investigate the co-oxidation of C-H bonds in substrates with different relative reactivities, the aim being to couple the oxidised products in situ to form the corresponding esters. Initial attempts were made to co-oxidise octane with toluene to form octyl benzoate using Au-Pd catalysts. During the study the oxidation of octane in the presence of benzaldehyde, an oxidation product of toluene, was also investigated in order to demonstrate the potential feasibility of the reaction. This work summarises our attempts to show whether a co-oxidation system could be an effective way to oxidise linear alkanes.
- Peneau, Virginie,Shaw, Greg,Freakley, Simon J.,Forde, Michael M.,Dimitratos, Nikolaos,Jenkins, Robert L.,Taylor, Stuart H.,Hutchings, Graham J.
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p. 3953 - 3959
(2015/08/03)
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- Revisiting the Influence of Silver in Cationic Gold Catalysis: A Practical Guide
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An excess amount of silver salt to generate cationic gold from a gold catalyst precursor such as L-Au-Cl almost always has adverse effects on the reactivity of the cationic gold catalyst. A preformed L-Au+X- complex, generated by sonication followed by centrifugation, increases the reactivity in a gold catalyzed reaction. The adverse silver effect might be caused by the interaction of silver salts with gold intermediates.
- Lu, Zhichao,Han, Junbin,Hammond, Gerald B.,Xu, Bo
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supporting information
p. 4534 - 4537
(2015/09/28)
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- Cobalt aminodiphosphine complexes as catalysts in the oxidation of n-octane
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Two types of cobalt aminodiphosphine complexes have been synthesized and characterized by IR spectroscopy, elemental analyses and single crystal X-ray diffraction. These are [Ph2PN(R)PPh2]CoCl2, 1 and [Ph2P(CH2)2N(R)(CH2)2PPh2]CoCl2, 2 where R = C6H11 (a); C5H11 (b); C3H7 (c). The functional groups on the nitrogen atom (R) were varied from a cyclohexyl ring, to n-pentyl alkyl chain, to an iso-propyl branched substituent. Complexes 2a and 2c were analyzed using single crystal X-ray diffraction. The geometry around the metal centers in 2a and 2c were distorted tetrahedral. All the complexes showed good activity as catalysts for the oxidation of n-octane using tert-butyl hydroperoxide (TBHP) as the oxidant. The complex bearing the flexible ligand backbone with the cyclohexyl substituent on the nitrogen atom was the most active and showed high selectivity towards ketones with 2-octanone being the dominant product.
- Naicker, Dunesha,Friedrich, Holger B.,Omondi, Bernard
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p. 63123 - 63129
(2015/08/06)
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- Catalytic Oxidation of Alkanes and Alkenes by H2O2 with a μ-Oxido Diiron(III) Complex as Catalyst/Catalyst Precursor
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A new μ-oxo diiron(III) complex of the lithium salt of the pyridine-based unsymmetrical ligand 3-[(3-{[bis(pyridin-2-ylmethyl)amino]methyl}-2-hydroxy-5-methylbenzyl)(pyridin-2-ylmethyl)amino]propanoate (LiDPCPMPP), [Fe2(μ-O)(LiDPCPMPP)2](ClO4)2, has been synthesized and characterized. The ability of the complex to catalyze oxidation of several alkanes and alkenes has been investigated by using CH3COOH/H2O2 (1:1) as an oxidative system. Moderate activity in cyclohexane oxidation (TOF = 33 h-1) and good activity in cyclohexene oxidation (TOF = 72 h-1) were detected. Partial retention of configuration (RC = 53%) in cis- and trans-1,2-dimethylcyclohexane oxidation, moderate 3/2 selectivity (4.1) in adamantane oxidation, and the observation of a relatively high kinetic isotope effect for cyclohexane oxidation (KIE = 3.27) suggest partial metal-based oxidation, probably in tandem with free-radical oxidation. Low-temperature UV/Vis spectroscopy and mass spectrometric studies in the rapid positive detection mode indicate the formation of a transient peroxido species, [Fe2(O)(O2)(LiDPCPMPP)2]2+, which might be an intermediate in the metal-based component of the oxidation process. A μ-oxido diiron(III) complex, [Fe2(μ-O)(LiDPCPMPP)2](ClO4)2, was synthesized and characterized. This complex was used as catalyst in C-H bond oxidation with CH3COOH-H2O2 as chemical oxidant. Reactivity studies indicate that the oxidation process goes through a metal-based mechanism concomitant with a radical process.
- Das, Biswanath,Al-Hunaiti, Afnan,Haukka, Matti,Demeshko, Serhiy,Meyer, Steffen,Shteinman, Albert A.,Meyer, Franc,Repo, Timo,Nordlander, Ebbe
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p. 3590 - 3601
(2015/08/06)
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- Addition reactions of organometallic reagents to nitrogen trifluoride and enhanced alkyl-alkyl coupling by NF3
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A survey of the reaction of nitrogen trifluoride (NF3) with various organometallic reagents finds that organomagnesium (Grignard) reagents are the most useful for producing N,N-difluoroaminoalkanes. Alkyl-alkyl coupling is a persistant side reaction. Organolithiums are marginally effective. Organocopper, organozinc reagents undergo primarily alkyl-alkyl coupling catalyzed by the presence of NF3. Organocalcium and organoaluminum reagents are unreactive.
- Belter, Randolph K.
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p. 110 - 113
(2015/04/27)
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- PROCESS FOR THE SYNTHESIS OF KETONES FROM INTERNAL ALKENES
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The present invention is directed to methods for oxidizing internal olefins to ketones. In various embodiments, each method comprising contacting an organic substrate, having an initial internal olefin, with a mixture of (a) a biscationic palladium salt; and (b) an oxidizing agent; dissolved or dispersed in a solvent system to form a reaction mixture, said solvent system comprising at least one C2-6 carbon nitrile and optionally at least one secondary alkyl amide, said method conducted under conditions sufficient to convert at least 50 mol % of the initial internal olefin to a ketone, said ketone positioned on a carbon of the initial internal olefin. The transformation occurs at room temperature and shows wide substrate scope. Applications to the oxidation of seed oil derivatives and a bioactive natural product are described.
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Paragraph 0122; 0124; 0149
(2014/07/22)
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- Highly efficient alkane oxidation catalyzed by [MnV(N)(CN) 4]2-. Evidence for [MnVII(N)(O)(CN) 4]2- as an active intermediate
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The oxidation of various alkanes catalyzed by [MnV(N)(CN) 4]2- using various terminal oxidants at room temperature has been investigated. Excellent yields of alcohols and ketones (>95%) are obtained using H2O2 as oxidant and CF3CH 2OH as solvent. Good yields (>80%) are also obtained using (NH4)2[Ce(NO3)6] in CF 3CH2OH/H2O. Kinetic isotope effects (KIEs) are determined by using an equimolar mixture of cyclohexane (c-C6H 12) and cyclohexane-d12 (c-C6D12) as substrate. The KIEs are 3.1 ± 0.3 and 3.6 ± 0.2 for oxidation by H2O2 and Ce(IV), respectively. On the other hand, the rate constants for the formation of products using c-C6H12 or c-C6D12 as single substrate are the same. These results are consistent with initial rate-limiting formation of an active intermediate between [Mn(N)(CN)4]2- and H2O2 or CeIV, followed by H-atom abstraction from cyclohexane by the active intermediate. When PhCH2C(CH3)2OOH (MPPH) is used as oxidant for the oxidation of c-C6H12, the major products are c-C6H11OH, c-C6H10O, and PhCH2C(CH3)2OH (MPPOH), suggesting heterolytic cleavage of MPPH to generate a Mn=O intermediate. In the reaction of H2O2 with [Mn(N)(CN)4]2- in CF 3CH2OH, a peak at m/z 628.1 was observed in the electrospray ionization mass spectrometry, which is assigned to the solvated manganese nitrido oxo species, (PPh4)[Mn(N)(O)(CN)4] -·CF3CH2OH. On the basis of the experimental results the proposed mechanism for catalytic alkane oxidation by [MnV(N)(CN)4]2-/ROOH involves initial rate-limiting O-atom transfer from ROOH to [Mn(N)(CN)4]2- to generate a manganese(VII) nitrido oxo active species, [MnVII(N)(O) (CN)4]2-, which then oxidizes alkanes (R'H) via a H-atom abstraction/O-rebound mechanism. The proposed mechanism is also supported by density functional theory calculations.
- Ma, Li,Pan, Yi,Man, Wai-Lun,Kwong, Hoi-Ki,Lam, William W.Y.,Chen, Gui,Lau, Kai-Chung,Lau, Tai-Chu
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p. 7680 - 7687
(2014/06/10)
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- Coordination chemistry of Co complexes containing tridentate SNS ligands and their application as catalysts for the oxidation of n-octane
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The selective oxidation of saturated hydrocarbons to terminal oxygenates under mild catalytic conditions has remained a centuries long challenge in chemical catalysis. In an attempt to address this challenge, two series of tridentate donor ligands {2,6-bis(RSCH2)pyridine and bis(RSCH2CH2)amine [R = alkyl, aryl]} and their respective cobalt complexes {Co[2,6-bis(RSCH2)pyridine]Cl2 and Co[bis(RSCH2CH2)amine]Cl2} were synthesized and characterized. Crystal structures of Co[2,6-bis(RSCH2)pyridine]Cl2 [R = -CH3 (1), -CH2CH3 (2), -CH2CH2CH2CH3 (3) and -C6H5 (4)] are reported in which 1 crystallized as a homo-bimetallic dimer that incorporated two bridging chloride atoms in an octahedral geometry around each cobalt center, while 2, 3 and 4 crystallized as mono-metallic species characterized by trigonal bipyramidal arrangement of ligands around each cobalt center. As catalysts for the homogeneous selective oxidation of n-octane, the catalysts yielded ketones as the dominant products with a selectivity of ca. 90% for the most active catalyst Co[bis(CH2CH2SCH2CH2)amine]Cl2 (6) at a total n-octane conversion of 23%. Using tert-butyl hydroperoxide (TBHP) as an oxidant, optimization of reaction conditions is also reported.
- Soobramoney, Lynette,Bala, Muhammad D.,Friedrich, Holger B.
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p. 15968 - 15978
(2015/01/08)
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- Carbonylative enantioselective meso-desymmetrization of cis-epoxides to trans-β-lactones: Effect of salen-ligand electronic variation on enantioselectivity
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Carbonylation catalysts for the desymmetrization of meso-epoxides yielding enantioenriched trans-β-lactones are reported. Fine-tuning the electronic properties of the ligand further improved enantioselectivity. The sterics of the substrate dictated whether a given electronic variation decreased or increased enantioenrichment, revealing an unexpected relationship between the substrate's steric environment and the electronic nature of the optimal catalyst.
- Mulzer, Michael,Lamb, Jessica R.,Nelson, Zachary,Coates, Geoffrey W.
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supporting information
p. 9842 - 9845
(2014/08/18)
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- Mn(ii) acetate: An efficient and versatile oxidation catalyst for alcohols
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A homogeneous catalytic system consisting of Mn(ii) acetate (18 μmol), tert-butylhydroperoxide (2.5 mmol), acetonitrile (1.5 mL) and trifluoroacetic acid (91 μmol) was developed for efficient and selective oxidation of various alcohols (1 mmol). The system yielded good to quantitative conversions (42-100%) of various secondary alcohols, such as 2-octanol, fenchyl alcohol and borneol, to their corresponding ketones. Primary alcohols, for example 1-octanol and differently substituted benzyl alcohols, were mainly converted to their corresponding carboxylic acids. Studies with a selection of hydrocarbons, tertiary amines and a cyclic ether isochroman showed that besides alcohols, other substrates can be oxidised as well.
- Raeisaenen, Minna T.,Al-Hunaiti, Afnan,Atosuo, Elisa,Kemell, Marianna,Leskelae, Markku,Repo, Timo
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p. 2564 - 2573
(2014/07/22)
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- N-alkylation of ammonia and amines with alcohols catalyzed by Ni-loaded CaSiO3
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Nickel nanoparticles loaded onto calcium silicate (Ni/CaSiO3) have been prepared by ion-exchange method followed by in situ H 2-reduction of the calcined precursor. Ni/CaSiO3 was found to be effective for the catalytic direct synthesis of primary amines from alcohols and NH3 under relatively mild conditions. Various aliphatic alcohols are tolerated, and the turnover number (TON) was higher than those of Ru-based homogeneous catalysts. The catalyst was recoverable and was reused. Effects of the surface oxidation states and particle size of Ni on the catalytic activity were studied by infrared (IR) investigation of the states of adsorbed CO and transmission electron microscopy (TEM). It is clarified that the surface Ni0 sites on small (3 nm) sized Ni nanoparticles are the catalytically active species. Ni/CaSiO3 was also effective for the alkylation of anilines and aliphatic amines with various alcohols (benzyl and aliphatic alcohols) under additive free conditions; primary amines were converted into secondary amines and secondary amines into tertiary amines.
- Shimizu, Ken-Ichi,Kanno, Shota,Kon, Kenichi,Hakim Siddiki,Tanaka, Hideyuki,Sakata, Yoshihisa
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p. 134 - 138
(2014/06/09)
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- Liquid phase oxidation of n-octane to C8 oxygenates over modified Fe-MOF-5 catalysts
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The Metal Organic Framework materials Fe4-MOF-5, Fe 2-Zn2-MOF-5 and Fe0.9-Zn3. 1-MOF-5 were prepared. The XRD results showed the expected pattern of MOF-5 with a very sharp peak at a 2θ value below 10° which indicate that the material is highly crystalline. The SEM and TEM images showed that the catalysts are cubic in shape. The synthesised Fe4-MOF-5, Fe 2-Zn2-MOF-5 and Fe0.9-Zn3. 1-MOF-5 were tested in the oxidation of n-octane using H 2O2 as an oxidant in acetonitrile as solvent. Conversions of 10.5, 4.2 and 3.6% were obtained for Fe4-MOF-5, Fe 2-Zn2-MOF-5 and Fe0.9-Zn3. 1-MOF-5 respectively. It was observed that primary carbon activation increased with decreasing Fe content, as C-1 selectivities of 9.5, 12.9 and 19.8% were achieved for Fe4-MOF-5, Fe2-Zn 2-MOF-5 and Fe0.9-Zn3.1-MOF-5 respectively. Only C8 oxygenate products were observed, which include 1-octanol, 2-octanol, 3-octanol, 4-octanol, octanal, 2-octanone, 3-octanone, 4-octanone and octanoic acid. Furthermore, these catalysts were tested in the oxidation of cyclohexane using H2O2 in acetonitrile. Selectivities of 48.3% for cyclohexanol, 47.1% for cyclohexanone and 4.6% for hydroperoxycyclohexane were recorded at a conversion of 40% using Fe 4-MOF-5 as a catalyst.
- Cele, Mduduzi N.,Friedrich, Holger B.,Bala, Muhammad D.
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- Liquid phase oxidation of n-octane to C8 oxygenates over modified Fe-MOF-5 catalysts
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The Metal Organic Framework materials Fe4-MOF-5, Fe2-Zn2-MOF-5 and Fe0.9-Zn3.1-MOF-5 were prepared. The XRD results showed the expected pattern of MOF-5 with a very sharp peak at a 2θ value below 10° which indicate that the material is highly crystalline. The SEM and TEM images showed that the catalysts are cubic in shape. The synthesised Fe4-MOF-5, Fe2-Zn2-MOF-5 and Fe0.9-Zn3.1-MOF-5 were tested in the oxidation of n-octane using H2O2as an oxidant in acetonitrile as solvent. Conversions of 10.5, 4.2 and 3.6% were obtained for Fe4-MOF-5, Fe2-Zn2-MOF-5 and Fe0.9-Zn3.1-MOF-5 respectively. It was observed that primary carbon activation increased with decreasing Fe content, as C-1 selectivities of 9.5, 12.9 and 19.8% were achieved for Fe4-MOF-5, Fe2-Zn2-MOF-5 and Fe0.9-Zn3.1-MOF-5 respectively. Only C8 oxygenate products were observed, which include 1-octanol, 2-octanol, 3-octanol, 4-octanol, octanal, 2-octanone, 3-octanone, 4-octanone and octanoic acid. Furthermore, these catalysts were tested in the oxidation of cyclohexane using H2O2in acetonitrile. Selectivities of 48.3% for cyclohexanol, 47.1% for cyclohexanone and 4.6% for hydroperoxycyclohexane were recorded at a conversion of 40% using Fe4-MOF-5 as a catalyst.
- Cele, Mduduzi N.,Friedrich, Holger B.,Bala, Muhammad D.
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- Practical and general palladium-catalyzed synthesis of ketones from internal olefins
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Make it simple! A convenient and general palladium-catalyzed oxidation of internal olefins to ketones is reported. The transformation occurs at room temperature and shows wide substrate scope. Applications to the oxidation of seed-oil derivatives and a bioactive natural product (see scheme) are described, as well as intriguing mechanistic features. Copyright
- Morandi, Bill,Wickens, Zachary K.,Grubbs, Robert H.
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supporting information
p. 2944 - 2948
(2013/04/10)
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- Wacker-type oxidation of internal alkenes using Pd(Quinox) and TBHP
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The Pd-catalyzed TBHP-mediated Wacker-type oxidation of internal alkenes is reported. The reaction uses 2-(4,5-dihydro-2-oxazolyl)quinoline (Quinox) as ligand and TBHP(aq) as oxidant to deliver single ketone constitutional isomer products in a predictable fashion from electronically biased olefins. This methodology is showcased through its application on an advanced intermediate in the total synthesis of the antimalarial drug artemisinin.
- Deluca, Ryan J.,Edwards, Jennifer L.,Steffens, Laura D.,Michel, Brian W.,Qiao, Xiaoxiao,Zhu, Chunyin,Cook, Silas P.,Sigman, Matthew S.
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p. 1682 - 1686
(2013/04/10)
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- Heterogeneous cobalt catalysts for the acceptorless dehydrogenation of alcohols
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A series of transition metal(M)-loaded TiO2 catalysts (M/TiO2) and Co-loaded catalysts on various support materials were prepared by an impregnation method, followed by in situ H2-reduction at 400 °C, and tested for the acceptor-free oxidation of cyclododecanol in the liquid phase. Among the catalysts including noble metal catalysts, Co/TiO2 showed the highest activity. In the presence of Co/TiO 2 (0.1-3 mol%) the dehydrogenation of various aliphatic secondary alcohols proceeded to afford the corresponding ketones. The catalyst was recoverable and was reused after the H2-reduction treatment. Based on the spectroscopic characterization of the catalyst combined with the studies on the effect of the Co oxidation states on the catalytic activity, it is clarified that the surface metallic Co sites with electron deficiency are the catalytically active species.
- Shimizu, Ken-Ichi,Kon, Kenichi,Seto, Mayumi,Shimura, Katsuya,Yamazaki, Hiroshi,Kondo, Junko N.
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p. 418 - 424
(2013/03/29)
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