- Selective ruthenium-catalyzed oxidation of 1,2:4,5-di-O-isopropylidene-β-D-fructopyranose and other alcohols with NaOCl
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Matrix presented The asymmetric epoxidation catalyst 1,2:4,5-di-O-isopropylidene-β-D-erythro-2,3-hexadiulo-2,6-pyranose 2 was obtained in high yield from 1,2:4,5-di-O-isopropylidene-β-D-fructopyranose 1 via a recyclable ruthenium-catalyzed hypochlorite oxidation protocol under biphasic conditions (MTBE/water) in the presence of an alkaline buffer (pH 9.5). Other secondary alcohols were also oxidized selectively to the correspondinq ketones.
- Gonsalvi, Luca,Arends, Isabel W. C. E.,Sheldon, Roger A.
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- Promoting effect of water for aliphatic primary and secondary alcohol oxidation over platinum catalysts in dioxane/aqueous solution media
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In the selective oxidation with air of 1-octanol and 2-octanol in 1,4-dioxane at 100 °C and 10 bar in the presence of carbon supported platinum catalysts, the catalytic activity could be impressively boosted by substitution of pure dioxane by increasing amounts of water. Changing the polarity of the solvent strongly influences the adsorption equilibrium of substrates and products at the catalyst surface and hence plays an influential role on the reaction rate.
- Frassoldati, Antonio,Pinel, Catherine,Besson, Michle
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- Engineering of P450pyr hydroxylase for the highly regio- and enantioselective subterminal hydroxylation of alkanes
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Terminal-selective cytochrome P450pyr has been successfully engineered through directed evolution for the subterminal hydroxylation of alkanes with excellent regio- and enantioselectivity. A sensitive colorimetric high-throughput screening (HTS) assay was developed for the measurement of both the regioselectivity and the enantioselectivity of a hydroxylation reaction. By using the HTS assay and iterative saturation mutagenesis, sextuple-mutant P450pyrSM1 was created for the hydroxylation of n-octane (1) to give (S)-2-octanol (2) with 98 % ee and >99 % subterminal selectivity. The engineered P450 is the first enzyme for this type of highly selective alkane hydroxylation, being useful for the Ci-H activation and functionalization of alkanes and the preparation of enantiopure alcohols. Molecular modeling provided structure-based understanding of the fully altered regioselectivity and the excellent enantioselectivity. Another sextuple-mutant P450pyrSM2 catalyzed the hydroxylation of propylbenzene (3) to afford (S)-1-phenyl-2-propanol (4) with 95 % ee and 98 % subterminal selectivity. Get a handle on it: Highly regio- and enantioselective subterminal hydroxylation of n-octane and propylbenzene was observed with P450 enzymes obtained by the directed evolution of terminal-selective P450pyr hydroxylase (see scheme). The engineered enzymes with their fully altered selectivities are useful for the functionalization of alkanes and the preparation of enantiomerically pure alcohols.
- Yang, Yi,Liu, Ji,Li, Zhi
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- A novel heteropolyanion-based amino-containing cross-linked ionic copolymer catalyst for epoxidation of alkenes with H2O2
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A heteropolyanion-based cross-linked ionic copolymer was prepared by the anion-exchange of a newly task-specific designed amino-containing ionic copolymer with a Keggin heteropolyacid, and characterized by FT-IR, SEM, TG, XRD, UV-vis, ESR, 1H NMR, and elemental analysis. Its catalytic activity was evaluated in the epoxidation of alkenes with aqueous H 2O2. The resultant heteropolyanion-based ionic copolymer is revealed to be a highly efficient heterogeneous catalyst for epoxidation of alkenes with H2O2, adding the advantages of convenient recovery and steady reuse.
- Leng, Yan,Zhang, Weijie,Wang, Jun,Jiang, Pingping
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- Microstructured Au/Ni-fiber catalyst for low-temperature gas-phase selective oxidation of alcohols
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Galvanic deposition of Au onto a thin-sheet sinter-locked 8 μm Ni-fiber delivers a high-performance Au/Ni-fiber catalyst for alcohol oxidation, due to the unique combination of excellent heat conductivity, remarkable low-temperature activity, and good stability/regenerability. The special NiO@Au ensembles formed during the reaction contribute to promoting the low-temperature activity. The Royal Society of Chemistry 2011.
- Zhao, Guofeng,Hu, Huanyun,Deng, Miaomiao,Lu, Yong
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- Gold supported on a biopolymer (chitosan) catalyzes the regioselective hydroamination of alkynes
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Gold nanoparticles on a polysaccharide-based support (chitosan) were found to catalyze with very high yields the regioselective hydroamination of alkynes without the need for acid promoters and inert atmosphere. The metal-support interactions were studied by Raman, IR, UV, and NMR spectroscopy. The interaction between gold and the NH and OH groups of chitosan allow good dispersion of the nanocrystals on the biopolymer. The chitosan-silica composite further stabilizes gold nanoparticles against agglomeration or leaching compared with other supports.
- Corma, Avelino,Concepcion, Patricia,Dominguez, Irene,Forne, Vicente,Sabater, Maria J.
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- New Cleavable Surfactants Derived from Glucono-1,5-Lactone
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New amido nonionic cleavable surfactants were synthesized in good yields by the acetalization of glucono-1,5-lactone with octanal, 2-octanone or 2-undecanone, followed by amidation with monoethanolamine, diethanolamine or morpholine.These compounds possessed good water solubilities.The compounds derived from 2-octanone showed higher critical micelle concentrations than the compounds from octanal.For the same hydrophobic chain, both the micelle-forming property and the ability to lower surface tension increased with the change in the terminal amide group in the orderdiethanolamide morpholide monoethanolamide.Interestingly, in spite of their relatively short hydrophobic chains, these compounds showed greater ability to lower surface tension than conventional nonionic surfactants, such as alcohol ethoxylates.Furthermore, their acid-decomposition properties were determined.Their decomposition rates were also compared with that of the corresponding carboxylate type of compound derived from glucono-1,5-lactone. KEY WORDS: Acid-decomposition properties, cleavable surfactant, glucono-1,5-lactone, sugar-derived surfactant, surface-active properties.
- Kida, Toshiyuki,Morishima, Nobuaki,Masuyama, Araki,Nakatsuji, Yohji
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- Selective oxidation of alcohols by orthorhombic Mo-V-O phase with molecular oxygen
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We have investigated heterogeneous oxidation of alcohols using crystalline molybdenum vanadium oxide (Mo-V-O) as catalyst with molecular oxygen as oxidant. The major product from primary alcohol was aldehyde, the secondary alcohol was mainly dehydrated to olefin, and the oxidation of cyclic alcohols chiefly afforded ketones. A Hammett plot suggested that hydride abstraction might be involved in the reaction step. We have discussed possible reaction mechanism based on substrate adsorption and activation on catalytically active sites. Copyright
- Wang, Feng,Ueda, Wataru
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- Evaluation of tuned phosphorus cavitands on catalytic cross-dimerization of terminal alkynes
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Synthesis of four new bis-phosphorus cavitands is described, including a description of their catalytic use on cross-dimerization of terminal alkynes. The commercially available P[N(CH2CH3)2]3, PhP[N(CH2CH3)2]2, P(OCH3)3, and in situ generated P(NMeBn)3were reacted with a tetra-ol cavitand platform to provide new phosphorus ligands. These ligands readily formed bis-Au complexes that were examined to generate a reactivity profile for the catalytic cross-dimerization of terminal alkynes. We found that the ligand derived from P[N(CH3)2]3gave best product selectivity.
- Endo, Naoki,Kanaura, Mao,Schramm, Michael P.,Iwasawa, Tetsuo
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- Application of hydrogen peroxide encapsulated in silica xerogels to oxidation reactions
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Hydrogen peroxide was encapsulated into a silica xerogel matrix by the sol-gel technique. The composite was tested as an oxidizing agent both under conventional and microwave conditions in a few model reactions: Noyori′s method of octanal and 2-octanol oxidation and cycloctene epoxidation in a 1,1,1-trifluoroethanol/Na2WO4 system. The results were compared with yields obtained for reactions with 30% H2O2 and urea-hydrogen peroxide (UHP) as oxidizing agents. It was found that the composite has activity similar to 30% H2O2 and has a several advantages over UHP such as the fact that silica and H2O are the only products of the composite decomposition or no contamination by urea or its derivatives occurs; the xerogel is easier to heated by microwave irradiation than UHP and could be used as both an oxidizing agent and as solid support for microwave assisted solvent-free oxidations.
- Bednarz, Szczepan,Rys, Barbara,Bogda, Dariusz
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- Fe(III) halides as effective catalysts in carbon-carbon bond formation: Synthesis of 1,5-dihalo-1,4-dienes, αβ-unsaturated ketones, and cyclic ethers
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(Chemical Equation Presented). Iron(III) halides have proven to be excellent catalysts in the coupling of acetylenes and aldehydes. When terminal acetylenes were used the main products obtained were 1,5-dihalo-1,4-dienes with (E,Z)-stereochemistry contaminated in some cases with (E)-α,β- unsaturated ketones. The former carbonyl derivatives were the sole products isolated when nonterminal aromatic alkynes were used. When homopropargylic alcohols were used, a Prins-type cyclization occurred yielding 2-alkyl-4-halo-5,6-dihydro-2H-pyrans. In addition, anhydrous ferric halides are also shown to be excellent catalysts for the standard Prins cyclization with homoallylic alcohols. Isolation of an intermediate acetal, calculations, and alkyne hydration studies provide substantiation of a proposed mechanism.
- Miranda, Pedro O.,Diaz, David D.,Padron, Juan I.,Ramirez, Miguel A.,Martin, Victor S.
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- ACTIVATION OF MOLECULAR OXYGEN. SELECTIVE OXIDATION OF TERMIANL OLEFINS AND ALCOHOLS CATALYZED BY CATIONIC COMPLEXES OF RHODIUM
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Rhodium(I) complexes containing hybrid "hemilabile" ligands of general formula + (R = Ph, Et, Me) are found to catalyze air oxidation of terminal olefins to the corresponding methyl ketones, of primary alcohols to acetals and of secondary alcohols to ketones.
- Bresaan, M.,Morandini, F.,Rigo, P.
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- Hydrophobic, low-loading and alkylated polystyrene-supported sulfonic acid for several organic reactions in water: Remarkable effects of both the polymer structures and loading levels of sulfonic acids
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The development of hydrophobic, low-loading and alkylated polystyrene-supported sulfonic acid for organic reactions was studied. The effects of both the polymer structures and loading levels of the sulfonic acid catalysts were also discussed. Hydrophobicity of the catalyst was considered as key for efficient catalysis.
- Iimura, Shinya,Manabe, Kei,Kobayashi, Shue
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- Solvent-free hydration of alkynes over Hβ zeolite
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Abstract An efficient and environmentally benign catalytic system has been successfully developed for highly Markovnikov selective hydration of various alkynes over heterogeneous catalyst (Hβ zeolite) in solvent-free conditions. The catalyst (Hβ zeolite) is commercial available, recyclable and exhibits excellent catalytic activity towards the hydration of alkynes to ketones. Moreover, the propargylic aryl carbinols undergo Meyer-Schuster rearrangement to give α,β-unsaturated carbonyl compounds in excellent yields.
- Mameda, Naresh,Peraka, Swamy,Marri, Mahender Reddy,Kodumuri, Srujana,Chevella, Durgaiah,Gutta, Naresh,Nama, Narender
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- Dialkylborane-catalyzed hydroboration of alkynes with 1,3,2-benzodioxaborole in tetrahydrofuran
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Dialkylborane catalyzed hydroboration of alkynes with an equimolar amount of 1,3,2-benzodioxaborole in tetrahydrofuran efficiently to provide 2-alkenyl-1,3,2-benzodioxaborole under mild reaction conditions.
- Arase,Hoshi,Mijin,Nishi
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- Facile Hydrolysis and Alcoholysis of Palladium Acetate
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Palladium(II) acetate is readily converted into [Pd3(μ2-OH)(OAc)5] (1) in the presence of water in a range of organic solvents and is also slowly converted in the solid state. Complex 1 can also be formed in nominally anhydrous solvents. Similarly, the analogous alkoxide complexes [Pd3(μ2-OR)(OAc)5] (3) are easily formed in solutions of palladium(II) acetate containing a range of alcohols. An examination of a representative Wacker-type oxidation shows that the Pd-OH complex 1 and a related Pd-oxo complex 4 can be excluded as potential catalytic intermediates in the absence of exogenous water. When is palladium acetate not palladium acetate? Anywhere near trace amounts of water or alcohols. Palladium acetate is extremely sensitive to hydrolysis in solution and moderately so in the solid state. The resulting hydroxide complex is likely to be the true starting point for many reactions and catalytic processes that are reported as using palladium acetate.
- Bedford, Robin B.,Bowen, John G.,Davidson, Russell B.,Haddow, Mairi F.,Seymour-Julen, Annabelle E.,Sparkes, Hazel A.,Webster, Ruth L.
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- Continuous biphasic enzymatic reduction of aliphatic ketones
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Biphasic reactions offer an attractive alternative for the utilisation of enzymes for conversion of hardly water soluble substrates. Especially, the alcohol dehydrogenase from Lactobacillus brevis was successfully used for the reductive synthesis of enantiopure secondary aliphatic alcohols. With the enzymatic catalyst and the cofactor effectively retained in the reactive aqueous phase, the continuous operation was demonstrated by continuous addition and withdrawal of the non-reactive phase. The four tested substrates 2-heptanone, 2-octanone, 2-nonanone, and 2-decanone showed that the space time yield and turnover numbers (TON) of the enzyme decrease as the availability of the substrate decreases with increasing partition coefficients. Nevertheless, a TONLbADH of up to 478 × 103 could be achieved. Remarkably, the cofactor utilisation turned out to be very high and a TON NADP+ of more than 20 × 103 was easily achievable for both 2-heptanone and 2-octanone by substrate coupled cofactor regeneration with excess of 2-propanol.
- Leuchs, Susanne,Nonnen, Thomas,Dechambre, Dominique,Na'Amnieh, Shukralla,Greiner, Lasse
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- Reactivity of Peroxopolyoxo Complexes. Oxidation of Thioethers, Alkenes, and Sulfoxides by Tetrahexylammonium Tetrakis(diperoxomolybdo)phosphate
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Kinetics of oxidation of thioethers, alkenes, and sulfoxides by tetrahexylammonium tetrakis(diperoxomolybdo)phosphate (TEAM) were performed in chloroform.The results obtained, compared with the corresponding data of a series of Mo(VI) peroxo complexes, rule out a nucleophilic oxygen transfer mechanism.Rather, the data point to Mo(VI) peroxopolyoxo complexes as well as simple peroxo complexes behave as electrophilic oxidants toward nucleophilic substrates such as thioethers and alkenes.A study of the countercation effects indicates that the increasing bulkiness of the cation reduces the electrophilicity of the peroxopolyoxo complex.W ith sulfoxides, incursion of SET processes might be a likely event.
- Ballistreri, Francesco P.,Bazzo, Adriana,Tomaselli, Gaetano A.,Toscano, Rosa M.
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- Desulphonylation of α-Nitrosulphones with N-Benzyl-1,4-dihydronicotinamide
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A sulphonyl group of α-nitrosulphones is replaced by hydrogen on treatment with N-benzyl-1,4-dihydronicotinamide; the reaction proceeds by a non-chain, free-radical process involving one-electron transfer.
- Ono, Noboru,Tamura, Rui,Tanikaga, Rikuhei,Kaji, Aritsune
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- A surfactant-like ionic liquid with permanganate dissolved as a highly selective epoxidation system
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A ligand-free catalytic epoxidation system using permanganate in a surfactant-like ionic liquid (IL) medium was developed. The results indicate that the IL takes crucial effects in the epoxide selectivity. The loading of permanganate is also found critical in preventing over-oxidation of epoxides. The system with 0.3 mol% permanganate and 3.5-equivalent CH3CO3H is able to achieve excellent yields and selectivity of epoxides. The study of epoxidation with KMnO4 in IL medium reveals an unusual oxidation behavior of permanganate not found in traditional solvents.
- Lu, Yu-Jing,Wong, Wing-Leung,Chow, Cheuk-Fai
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- HOMOGENEOUS OXIDATION OF 1-OCTENE BY t-BUTYL HYDROPEROXIDE CATALYZED BY RHODIUM(III) SPECIES
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Chlororhodium(III) complexes catalyze the oxidation of oct-1-ene by t-BuOOH in R1R2CHOH, to yield products of dioxygen oxidation: i.e. the methyl ketone resulting from olefin oxidation, the acetal or ketone formed by solvent cooxidation, and isomerized olefins.
- Faraj, Mahmoud,Bregeault, Jean-Marie,Martin, Jacques,Martin, Claudine
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- Ordered nanoporous lyotropic liquid crystal polymer resin for heterogeneous catalytic aerobic oxidation of alcohols
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An ordered, nanoporous, TEMPO-based polymer resin formed from lyotropic liquid crystal monomers catalyzes the hetereogeneous oxidation of alcohols with high activity and substrate size selectivity under transition-metal-free, aerobic conditions.
- Dwulet, Gregory E.,Gin, Douglas L.
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- Catalyse par le palladium at la lumiere ultra-violette de l'oxydation d'alcenes par l'oxygene moleculaire
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The light-promoted oxidation of terminal alkenes by oxygen in the presence of catalytic amounts of palladium(II) complexes led to corresponding α,β-ethylenic carbonyl compounds and methyl ketones; rapid and extensive isomerisation of the starting alkene is observed.The effect of acetone as solvent on the efficiency of these oxidations is discussed.
- Muzart, Jacques,Pale, Patrick,Pete, Jean-Pierre
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- Gold nanoparticles supported on layered TiO2-RGO hybrid as an enhanced and recyclable catalyst for microwave-assisted hydration reaction
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In this study, we synthesized a novel composite material (Au-TiO2-RGO) consisting of tiny gold nanoparticles (～4.5 nm) grown on a layered titania (TiO2) and reduced graphene oxide (RGO) hybrid. After treatment with microwave and sulfuric acid, solid acid (SO42-/TiO2) was in situ formed on the surface of TiO2, and the resulting Au-SO42-/TiO2-RGO was determined as an enhanced catalyst for hydration reaction. The strong metal-support interaction (SMSI) between Au and TiO2 and the cooperative effect between Au and SO42-/TiO2 solid acid collectively account for the excellent performance. Moreover, due to the versatile RGO substrate, the catalyst could also be recycled and reused at least 5 times without obvious deactivation.
- Cheng, Yunfeng,Zhao, Qingshan,Li, Yang,Peng, Wenchao,Zhang, Guoliang,Zhang, Fengbao,Fan, Xiaobin
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- Regioselective 1,4-Addition to α,β-Unsaturated Ketones with Grignard Reagents Mediated by (N,N,N',N'-Tetramethylethylenediamine)zinc(II) Chloride
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The reaction of α,β-unsaturated ketones with a THF solution RMgX (3 mol equiv) and ZnCl2*TMEDA (1 mol equiv) followed by NH4Cl gave 1,4-addition products.The products were contaminated by 1,2-addition products when R = Ph and Me but were essentially free of those compounds when R = n-Bu or i-Pr.The yields were highest when X = Cl.Thus the reaction of 2-cyclohexen-1-one with a solution of n-BuMgCl and ZnCl2*TMEDA gave 3-n-butylcyclohexanone (1) in 96percent yield.
- Kjonaas, Richard A.,Vawter, Edward J.
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- A Very Useful and Efficient Wacker Oxidation of Higher α-Olefins in the Presence of Per(2,6-di-O-methyl)-β-Cyclodextrin
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Oxidation of higher α-olefins (C8-C16) in a two phase system with a multicomponent catalytic system, i.e.PdSO4/H9PV6Mo6O40/CuSO4 and per(2,6-di-O-methyl)-β-cyclodextrin gives the corresponding 2-ketones in high yields ( >90 percent)
- Monflier, Eric,Tilloy, Sebastien,Fremy, Georges,Barbaux, Yolande,Mortreux, Andre
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- Preparation and reactivity of cyanocuprates containing alkylseleno and alkyltelluro groups as non-transferable ligands
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Alkylseleno and alkyltelluro groups are efficient non-transferable ligands of cyanocuprates in 1,4-addition reactions to enones.
- Zinn, Fabiano K.,Ramos, Eduardo C.,Comasseto, Jo?o V.
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- PHOTOACTIVATION OF ALKENE OXIDATION BY MOLECULAR OXYGEN IN THE PRESENCE OF PALLADIUM
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A catalytic cycle which leads to α-β ethylenic ketones and methyl ketones from terminal alkenes in the presence of palladium trifluoroacetate, oxygen and U.V. light is described.
- Muzart, Jacques,Pale, Patrick,Pete, Jean-Pierre
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- A Two-Step Oxidative Cleavage of 1,2-Diol Fatty Esters into Acids or Nitriles by a Dehydrogenation–Oxidative Cleavage Sequence
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Dehydrogenative oxidation of vicinal alcohols catalyzed by a commercially 64 wt.% Ni/SiO2 catalyst leads to the formation of α-hydroxyketone. This first step was developed without additional solvent according to two protocols: “under vacuum” or “with an olefin scavenger”. The synthesis of ketols was carried out with good conversions and selectivities. The recyclability of the supported nickel was also studied. Acyloin was then cleaved with oxidative reagent “formic acid/hydrogen peroxide”, which is cheap and can be used on a large scale for industrial oxidation processes. The global yield of this sequential system was up to 80 % to pelargonic acid and azelaic acid monomethyl ester without intermediate purification. By treating the acyloin intermediate with hydroxylamine, nitriles were obtained with a good selectivity.
- Guicheret, Boris,Bertholo, Yann,Blach, Philippe,Raoul, Yann,Métay, Estelle,Lemaire, Marc
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- MILD REDUCTION OF α-HALO KETONES TO KETONES PROMOTED BY PI3 OR P2I4
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PI3 and P2I4 cleanly reduce α-bromo and α-iodo ketones to ketones
- Denis, J. N.,Krief, A.
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- Oxidation of Olefins to Aldehydes Using a Palladium-Copper Catalyst
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Wacker-like catalysts using tert-butyl alcohol as the solvent oxidize terminal olefins to give unusually high selectivities for aldehydes and also provide some insight into the role of copper and oxygen in Wacker-like reactions.
- Wenzel, Timothy T.
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- Phase transfer catalyzed oxidation of alcohols with sodium hypochlorite
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Phase transfer catalyzed oxidation of alcohols with sodium hypochlorite in ethyl acetate media resulted in good to excellent yield of oxidized products. These reactions are mild, efficient, and safe. The experimental procedures and work-ups are very convenient.
- Mirafzal, Gholam A.,Lozeva, Albena M.
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- Hydration of terminal alkynes to aldehydes in aqueous micellar solutions by ruthenium(II) catalysis; first anti-Markovnikov addition of water to propargylic alcohols
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The hydration of terminal alkynes and of propargylic alcohols to the corresponding aldehyde derivatives is conveniently carried out at 60°C in an aqueous micellar environment, in the presence of 5 mol% of the indenyl ruthenium(II) complex [Ru(η5-C9H7)Cl(PPh3) 2]. Higher yields and improved regioselectivity of aldehyde versus ketone as well as reaction conditions, in particular temperature and catalyst load, are found with respect to a solvent mixture 2-propanol-water, due to the aggregating conditions of the micellar solution. The reactions of the propargylic alcohols indicate the tolerance of the hydroxy functionality by the ruthenium complex.
- Alvarez, Patricia,Bassetti, Mauro,Gimeno, José,Mancini, Giovanna
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- Cyclodextrin-Palladium Chloride.New Catalytic System for Selective Oxidation of Olefins to Ketones
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Terminal olefins are oxidized to ketones in high yields under mild conditions using palladium chloride and cyclodextrins as catalysts in two-phase systems; cyclodextrins show substrate selectivity.
- Harada, Akira,Hu, Ying,Takahashi, Shigetoshi
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- Magnetically Recoverable N-Heterocyclic Carbene-Gold(I) Catalyst for Hydroamination of Terminal Alkynes
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We prepared a magnetically recoverable gold(I) catalyst by immobilizing an N-heterocyclic carbene-gold(I) complex on magnetite and applied it to the hydroamination of alkynes. By employing 2 mol% of the magnetite-supported gold(I) catalyst, the hydroamination of terminal alkynes proceeded smoothly to provide the corresponding imine in a fair chemical yield. Moreover, after the reaction, the magnetic gold(I) catalyst was readily recovered by use of an external magnet and could be reused up to five times.
- Fujita, Ken-Ichi,Fujii, Akira,Sato, Junichi,Yasuda, Hiroyuki
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- CONJUGATE ADDITION TO α,β-UNSATURATED KETONES WITH MIXED LITHIUM TRIORGANOZINCATES
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Lithium Triorganozincates of the type RR'2ZnLi, where R'=Me and R=n-Bu or sec-Bu, efficiently transfer the R group in a 1,4 fashion to α,β-unsaturated ketones.
- Watson, Randall A.,Kjonaas, Richard A.
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- From Deep Eutectic Solvents to Nitrogen-rich Ordered Mesoporous Carbons: A Powerful Host for the Immobilization of Palladium Nanoparticles in the Aerobic Oxidation of Alcohols
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The preparation of a nitrogen-rich ordered mesoporous carbon (DNOMC) with three-dimensional cubic structure was established via carbonization of a green, inexpensive and safe deep eutectic solvent consisting of choline chloride salt and D-glucose in the presence of KIT-6 template for the first time. The materials were characterized by TEM, N2 adsorption–desorption analysis, XPS, TGA, CHN, and FT-IR. The DNOMC was shown to be a powerful support for the immobilization of palladium nanoparticles. The Pd@DNOMC catalyst exhibited high activity in the selective aerobic oxidation of various activated and non-activated primary and secondary benzylic as well as linear and cyclic aliphatic alcohols to the corresponding carboxylic acids and ketones in pure water under molecular oxygen. The catalyst system could successfully be reused at least ten times without any significant decrease in either activity or selectivity. It is worth noting that, the hot filtration strongly showed that the catalyst works in a boomerang-type catalyst pathway.
- Karimi, Babak,Vali, Hojatollah,Zahra Alizadeh, Seyedeh
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- Diverse Mechanistic Pathways in Single-Site Heterogeneous Catalysis: Alcohol Conversions Mediated by a High-Valent Carbon-Supported Molybdenum-Dioxo Catalyst
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With the increase in the importance of renewable resources, chemical research is shifting focus toward substituting petrochemicals with biomass-derived analogues and platform-molecule transformations such as alcohol processing. To these ends, in-depth mechanistic understanding is key to the rational design of catalytic systems with enhanced activity and selectivity. Here we discuss in detail the structure and reactivity of a single-site active carbon-supported molybdenum-dioxo catalyst (AC/MoO2) and the mechanism(s) by which it mediates alcohol dehydration. A range of tertiary, secondary, and primary alcohols as well as selected bio-based terpineols are investigated as substrates under mild reaction conditions. A combined experimental substituent effect/kinetic/kinetic isotope effect/EXAFS/DFT computational analysis indicates that (1) water assistance is a key element in the transition state; (2) the experimental kinetic isotopic effect and activation enthalpy are 2.5 and 24.4 kcal/mol, respectively, in good agreement with the DFT results; and (3) several computationally identified intermediates including Mo-oxo-hydroxy-alkoxide and cage-structured long-range water-coordinated Mo-dioxo species are supported by EXAFS. This structurally and mechanistically well-characterized single-site system not only effects efficient transformations but also provides insight into rational catalyst design for future biomass processes.
- Bedzyk, Michael J.,Das, Anusheela,Kratish, Yosi,Li, Jiaqi,Ma, Qing,Marks, Tobin J.
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p. 1247 - 1257
(2022/02/07)
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- Expanding the Biocatalytic Toolbox with a New Type of ene/yne-Reductase from Cyclocybe aegerita
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This study introduces a new type of ene/yne-reductase from Cyclocybe aegerita with a broad substrate scope including aliphatic and aromatic alkenes/alkynes from which aliphatic C8-alkenones, C8-alkenals and aromatic nitroalkenes were the preferred substrates. By comparing alkenes and alkynes, a ～2-fold lower conversion towards alkynes was observed. Furthermore, it could be shown that the alkyne reduction proceeds via a slow reduction of the alkyne to the alkene followed by a rapid reduction to the corresponding alkane. An accumulation of the alkene was not observed. Moreover, a regioselective reduction of the double bond in α,β-position of α,β,γ,δ-unsaturated alkenals took place. This as well as the first biocatalytic reduction of different aliphatic and aromatic alkynes to alkanes underlines the novelty of this biocatalyst. Thus with this study on the new ene-reductase CaeEnR1, a promising substrate scope is disclosed that describes conceivably a broad occurrence of such reactions within the chemical landscape.
- Karrer, Dominik,Gand, Martin,Rühl, Martin
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p. 2191 - 2199
(2021/02/26)
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- Dioxomolybdenum(VI) complexes of hydrazone phenolate ligands - syntheses and activities in catalytic oxidation reactions
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The new cis-dioxomolybdenum (VI) complexes [MoO2(L2)(H2O)] (2) and [MoO2(L3)(H2O)] (3) containing the tridentate hydrazone-based ligands (H2L2 = N'-(3,5-di-tert-butyl-2-hydroxybenzylidene)-4-methylbenzohydrazide and H2L3 = N'-(2-hydroxybenzylidene)-2-(hydroxyimino)propanehydrazide) have been synthesized and characterized via IR, 1H and 13C NMR spectroscopy, mass spectrometry, and single crystal X-ray diffraction analysis. The catalytic activities of complexes 2 and 3, and the analogous known complex [MoO2(L1)(H2O)] (1) (H2L1 = N'-(2-hydroxybenzylidene)-4-methylbenzohydrazide) have been evaluated for various oxidation reactions, viz. oxygen atom transfer from dimethyl sulfoxide to triphenylphosphine, sulfoxidation of methyl-p-tolylsulfide or epoxidation of different alkenes using tert-butyl hydroperoxide as terminal oxidant. The catalytic activities were found to be comparable for all three complexes, but complexes 1 and 3 showed better catalytic performances than complex 2, which contains a more sterically demanding ligand than the other two complexes.
- Hossain, Md Kamal,Plutenko, Maxym O.,Schachner, J?rg A.,Haukka, Matti,M?sch-Zanetti, Nadia C.,Fritsky, Igor O.,Nordlander, Ebbe
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- 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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- Trans(Cl)-2,2′-bipyridinedicarbonyldichlororuthenium(II) complex catalyzed oxidation of olefins, aryl hydrocarbons and alcohols in homogeneous phase
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Catalytic oxidation of organic substrates has wide applications in chemical industries due to which huge extensive research work is continuously going on throughout the world. Present study reports efficacious use of Trans (Cl)-2,2′-bipyridinedicarbonyldichlororuthenium(II) complex catalyzed oxidation of internal and terminal olefins, aryl hydrocarbons and alcohols. CH2Cl2–C2H5OH (6:4) was suitable solvent system for these oxidation reactions. The normal pressure oxidation reaction has been carried out at 1 ?atm. Pressure of oxygen and at 300C. The high pressure oxidation reaction was done at 4.48 ?× ?103 KNm3 pressure of oxygen and at 600C. No diminished catalytic activity was observed while checking the recyclability of catalyst up to 6–8 catalytic runs. Catalytic activity was also investigated using tert-butyl hydroperoxide as oxidant inspite of di-oxygen. Effect of different parameters on the rate of oxidation was also studied i.e. extra ligand, temperature, solvents, acids and bases. Kinetic studies have been done and on the basis of kinetics, the mechanism is proposed.
- Sharma, Varsha,Pant, Bhawana,Prakash, Deep,Sagar, Priyanka
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- A further step to sustainable palladium catalyzed oxidation: Allylic oxidation of alkenes in green solvents
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The palladium catalyzed oxidation of alkenes with molecular oxygen is a synthetically important reaction which employs palladium catalysts in solution; therefore, a solvent plays a critical role for the process. In this study, we have tested several green solvents as a reaction medium for the allylic oxidation of a series of alkenes. Dimethylcarbonate, methyl isobutyl ketone, and propylene carbonate, solvents with impressive sustainability ranks and very scarcely exploited in palladium catalyzed oxidations, were proved to be excellent alternatives for the solvents conventionally employed in these processes, such as acetic acid. Palladium acetate alone or in the combination with p-benzoquinone efficiently operates as the catalyst for the oxidation of alkenes by dioxygen under 5–10 atm. For most substrates, the systems in green solvents showed better selectivity for allylic oxidation products as compared to pure acetic acid; moreover, the reactions in propylene carbonate solutions occurred even faster than in acetic acid.
- dos Santos Costa, Maíra,de Camargo Faria, Amanda,Mota, Rayssa L.V.,Gusevskaya, Elena V.
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- Hydration of Alkynes to Ketones with an Efficient and Practical Polyoxomolybdate-based Cobalt Catalyst
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Hydration of alkynes to ketones is one of the most atom economical and universal methods for the synthesis of carbonyl compounds. However, the basic reaction usually requires organic ligand catalysts or harsh reaction conditions to insert oxygen into the C≡C bond. Here, we report an inorganic ligand supported cobalt (III) catalyst, (NH4)3[CoMo6O18(OH)6], which is supported by a central cobalt (III) mononucleus and a ring-shaped pure inorganic ligand composed of six MoVIO6 octahedrons to avoid the disadvantages of expensive and unrecyclable organic ligand catalysts or noble metal catalysts. Under mild conditions, the cobalt (III) catalyst can be used for the hydration of alkynes to ketones. The catalyst is non-toxic, green, and environment friendly. The catalyst can be recycled at least six times with high activity. According to control experiments, a reasonable mechanism is provided.
- Xie, Ya,Wang, Jingjing,Wang, Yunyun,Han, Sheng,Yu, Han
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p. 4985 - 4989
(2021/10/12)
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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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- Liquid-phase oxidation of olefins with rare hydronium ion salt of dinuclear dioxido-vanadium(V) complexes and comparative catalytic studies with analogous copper complexes
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Homogeneous liquid-phase oxidation of a number of aromatic and aliphatic olefins was examined using dinuclear anionic vanadium dioxido complexes [(VO2)2(salLH)]? (1) and [(VO2)2(NsalLH)]? (2) and dinuclear copper complexes [(CuCl)2(salLH)]? (3) and [(CuCl)2(NsalLH)]? (4) (reaction of carbohydrazide with salicylaldehyde and 4-diethylamino salicylaldehyde afforded Schiff-base ligands [salLH4] and [NsalLH4], respectively). Anionic vanadium and copper complexes 1, 2, 3, and 4 were isolated in the form of their hydronium ion salt, which is rare. The molecular structure of the hydronium ion salt of anionic dinuclear vanadium dioxido complex [(VO2)2(salLH)]? (1) was established through single-crystal X-ray analysis. The chemical and structural properties were studied using Fourier transform infrared (FT-IR), ultraviolet–visible (UV–Vis), 1H and 13C nuclear magnetic resonance (NMR), electrospray ionization mass spectrometry (ESI-MS), electron paramagnetic resonance (EPR) spectroscopy, and thermogravimetric analysis (TGA). In the presence of hydrogen peroxide, both dinuclear vanadium dioxido complexes were applied for the oxidation of a series of aromatic and aliphatic alkenes. High catalytic activity and efficiency were achieved using catalysts 1 and 2 in the oxidation of olefins. Alkenes with electron-donating groups make the oxidation processes easy. Thus, in general, aromatic olefins show better substrate conversion in comparison to the aliphatic olefins. Under optimized reaction conditions, both copper catalysts 3 and 4 fail to compete with the activity shown by their vanadium counterparts. Irrespective of olefins, metal (vanadium or copper) complexes of the ligand [salLH4] (I) show better substrate conversion(%) compared with the metal complexes of the ligand [NsalLH4] (II).
- Maurya, Abhishek,Haldar, Chanchal
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- METHOD FOR CONVERTING HYDROXYL GROUP OF ALCOHOL
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The present invention relates to: a method for converting a hydroxyl group of an alcohol; and a catalyst which makes the method possible. A method for converting a hydroxyl group of an alcohol according to the present invention is characterized by producing a compound represented by CH(R1)(R2)Nu (wherein R1, R2 and Nu are as defined below) by reacting an alcohol represented by CH(R1)(R2)OH (wherein each of R1 and R2 represents a hydrogen atom, an optionally substituted alkyl group, or the like) and a compound having an active proton, which is represented by H-Nu (wherein Nu represents a group represented by —CHX1-EWG1 or —NR3R4; X1 represents a hydrogen atom or the like; EWG1 represents an electron-withdrawing group; and each of R3 and R4 represents a hydrogen atom, an optionally substituted alkyl group, or the like), with each other in the presence of a complex of a group 7-11 metal of the periodic table and at least one solid base that is selected from the group consisting of layered double hydroxides, composite oxides and calcium hydroxide.
- -
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Paragraph 0489-0492
(2021/02/19)
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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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- Palladium/Copper-catalyzed Oxidation of Aliphatic Terminal Alkenes to Aldehydes Assisted by p-Benzoquinone
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The development of an anti-Markovnikov Wacker-type oxidation for simple aliphatic alkenes is a significant challenge. Herein, a variety of aldehydes can be selectively obtained from various unbiased aliphatic terminal alkenes using PdCl2(MeCN)2/CuCl in the presence of p-benzoquinone (BQ) under mild reaction conditions. Isomerization of the terminal alkene to the internal alkene was suppressed via slow addition of the starting material to the reaction mixture. In addition to the Pd catalyst, CuCl and BQ were essential in order to obtain the anti-Markovnikov product with high selectivity. Terminal alkenes bearing a halogen substituent afforded their corresponding aldehydes with high anti-Markovnikov selectivity. The halogen acts as a directing group in the reaction. DFT calculations indicate that a μ-chloro Pd(II)?Cu(I) bimetallic species with BQ coordinated to Cu is the catalytically active species in the case of a terminal alkene without a directing group.
- Komori, Saki,Yamaguchi, Yoshiko,Murakami, Yuka,Kataoka, Yasutaka,Ura, Yasuyuki
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p. 3946 - 3955
(2020/07/06)
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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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- Catalytic Oxidative Deamination by Water with H2Liberation
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Selective oxidative deamination has long been considered to be an important but challenging transformation, although it is a common critical process in the metabolism of bioactive amino compounds. Most of the synthetic methods developed so far rely on the use of stoichiometric amounts of strong and toxic oxidants. Here we present a green and efficient method for oxidative deamination, using water as the oxidant, catalyzed by a ruthenium pincer complex. This unprecedented reaction protocol liberates hydrogen gas and avoids the use of sacrificial oxidants. A wide variety of primary amines are selectively transformed to carboxylates or ketones in good to high yields. It is noteworthy that mechanistic experiments and DFT calculations indicate that in addition to serving as the oxidant, water also plays an important role in assisting the hydrogen liberation steps involved in amine dehydrogenation.
- Tang, Shan,Rauch, Michael,Montag, Michael,Diskin-Posner, Yael,Ben-David, Yehoshoa,Milstein, David
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supporting information
p. 20875 - 20882
(2020/12/23)
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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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- Hydration of terminal alkynes catalyzed by cobalt corrole complex
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Cobalt(III) corrole was firstly applied to the hydration of terminal alkynes. The alkyne hydration proceeded in good to excellent yield with 0.03 to 0.3 mol% cobalt corrole catalyst loading. A wide range of substrates were tolerated. Particularly, the reaction can give 90% yield in a gram scale experiment.
- Lai, Jia-Wei,Liu, Zhao-Yang,Chen, Xiao-Yan,Zhang, Hao,Liu, Hai-Yang
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supporting information
(2020/10/02)
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- Polyphenylene-Based Solid Acid as an Efficient Catalyst for Activation and Hydration of Alkynes
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Porous polymer catalysts possess the potential to combine the advantages of heterogeneous and homogeneous catalysis, namely, easy postreaction recycling and high dispersion of active sites. Here, we designed a -SO3H functionalized polyphenylene (PPhen) framework with purely sp2-hybridized carbons, which exhibited high activity in the hydration of alkynes including challenging aliphatic substrates such as 1-octyne. The superiority of the structure lies in its covalent crosslink in the xy-plane with a π-πstacking interaction between the planes, enabling simultaneously high swellability and porosity (653 m2·g-1). High acidic site density (2.12 mmol·g-1) was achieved under a mild sulfonation condition. Similar turnover frequencies (0.015 ± 0.001 min-1) were obtained regardless of acidic density and crosslink content, suggesting high accessibility for all active sites over PPhen. In addition, the substituted benzene groups can activate alkynes through a T-shape CH/πinteraction, as indicated by the 8 and 16 cm-1 red shift of the alkyne C-H stretching peak for phenylacetylene and 1-octyne, respectively, in the infrared (IR) spectra. These advantages render PPhen-SO3H a promising candidate as a solid catalyst replacing the highly toxic liquid phase acids such as the mercury salt.
- Gu, Hao,Kang, Liqun,Liu, Yiyun,Stamatopoulos, Apostolos,Wang, Bolun,Wang, Feng Ryan
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p. 4375 - 4382
(2020/06/09)
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- Catalytic Activity of a Zr MOF Containing POCOP-Pd Pincer Complexes
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A metal-organic framework assembled from POCOP-Pd pincer complex metallolinkers (1-PdBF4, Zr6O4(OH)4(L-PdMeCN)3(BF4)3, L = (2,6-(OPAr2)2C6H3, Ar = p-C6H4CO2-) has been generated via postsynthetic oxidative I-/BF4- ligand exchange with NOBF4. 1-PdBF4 catalyzes a range of organic transformations, including transfer hydrogenation of unsaturated organic substrates, terminal alkyne hydration, and intramolecular hydroarylation of alkynes. The homogeneous analogue, tBu4POCOP-PdBF4, shows poor catalytic activity for transfer hydrogenation and alkyne hydration and decomposes under the catalytic reaction conditions. Solubility limitations and catalyst deactivation pathways observed for the homogeneous pincer complex propound the advantages of using porous solid supports to immobilize organometallic species.
- Kassie, Abebu A.,Wade, Casey R.
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p. 2214 - 2221
(2020/07/06)
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- A tunable synthesis of either benzaldehyde or benzoic acid through blue-violet LED irradiation using TBATB
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In this paper, a highly efficient, metal-free, and homogeneous method for the selective aerobic photooxidation of alcohols and photooxidative-desilylation of tert-butyldimethylsilyl ethers (TBDMS) in the presence of tetrabutylammonium tribromide (TBATB) under irradiation of visible light was reported. The light source: blue (460 nm) and violet (400 nm) LED, can control selective oxidation to aldehyde or carboxylic acid.
- Mardani, Atefeh,Heshami, Marouf,Shariati, Yadollah,Kazemi, Foad,Abdollahi Kakroudi, Mazaher,Kaboudin, Babak
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- Selective and solventless oxidation of organic sulfides and alcohols using new supported molybdenum (VI) complex in microwave and conventional methods
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A new dioxo-molybdenum (VI) complex supported on functionalized Merrifield resin (MR-Mo) has been synthesized and characterized by elemental, scanning electron mcroscopy, energy-dispersive X-ray analysis, TGA, Brunauer–Emmett–Teller method, powder-X-ray d
- Das, Siva Prasad,Boruah, Jeena Jyoti
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- Aqueous extract of Shikakai; a green solvent for deoximation reaction: Mechanistic approach from experimental to theoretical
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This article describes a green method for regeneration of carbonyl compounds from various types of oxime compounds under microwave radiation using I2 and aqueous saponin solution isolated from Shikakai. Effect of saponin concentration on yield percentage of regenerated different types of carbonyl compounds has been discussed. A correlation has been established between saponin concentration and yield percentage of carbonyl compounds. Mechanism of interaction between oxime and saponin is established on the basis of density functional theory. In addition, the quantum chemical parameters for saponin have been determined. Furthermore, electrostatic surface analysis of the saponin is carried out to confirm the mechanism of interaction between saponin and oximes.
- Das, Debadutta,Kudrat-E-Zahan, Md.,Mahal, Ahmed,Mohapatra, Ranjan K.,Parhi, Pankaj K.,Sahu, Raghaba,Sarangi, Ashish K.
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- H2-free Synthesis of Aromatic, Cyclic and Linear Oxygenates from CO2
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The synthesis of oxygenate products, including cyclic ketones and phenol, from carbon dioxide and water in the absence of gas-phase hydrogen has been demonstrated. The reaction takes place in subcritical conditions at 300 °C and pressure at room temperature of 25 barg. This is the first observation of the production of cyclic ketones by this route and represents a step towards the synthesis of valuable intermediates and products, including methanol, without relying on fossil sources or hydrogen, which carries a high carbon footprint in its production by conventional methods. Inspiration for these studies was taken directly from natural processes occurring in hydrothermal environments around ocean vents. Bulk iron and iron oxides were investigated to provide a benchmark for further studies, whereas reactions over alumina and zeolite-based catalysts were employed to demonstrate, for the first time, the ability to use catalyst properties such as acidity and pore size to direct the reaction towards specific products. Bulk iron and iron oxides produced methanol as the major product in concentrations of approximately 2–3 mmol L?1. By limiting the hydrogen availability through increasing the initial CO2/H2O ratio the reaction could be directed to yield phenol. Alumina and zeolites were both observed to enhance the production of longer-chained species (up to C8), likely owing to the role of acid sites in catalysing rapid oligomerisation reactions. Notably, zeolite-based catalysts promoted the formation of cyclic ketones. These proof-of-concept studies show the potential of this process to contribute to sustainable development through either targeting methanol production as part of a “methanol economy” or longer-chained species including phenol and cyclic ketones.
- Gomez, Laura Quintana,Shehab, Amal K.,Al-Shathr, Ali,Ingram, William,Konstantinova, Mariia,Cumming, Denis,McGregor, James
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p. 647 - 658
(2020/01/24)
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- Generation and reaction of alkyl radicals in open reaction vessels
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An operationally simple process to transform alkyl iodides into reactive alkyl radicals is described. Aryl diazonium salts react with Hantzsch esters and molecular oxygen to give aryl radicals, which participate in halogen atom transfers to give alkyl radicals. These intermediates react with a variety of acceptors. The reaction cascade occurs at room temperature, in open reaction vessels, with short reaction times. This journal is
- McErlean, Christopher S. P.,Tatunashvili, Elene
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supporting information
p. 7818 - 7821
(2020/11/02)
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- The formyloxyl radical: Electrophilicity, C-H bond activation and anti-Markovnikov selectivity in the oxidation of aliphatic alkenes
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In the past the formyloxyl radical, HC(O)O, had only been rarely experimentally observed, and those studies were theoretical-spectroscopic in the context of electronic structure. The absence of a convenient method for the preparation of the formyloxyl radical has precluded investigations into its reactivity towards organic substrates. Very recently, we discovered that HC(O)O is formed in the anodic electrochemical oxidation of formic acid/lithium formate. Using a [CoIIIW12O40]5- polyanion catalyst, this led to the formation of phenyl formate from benzene. Here, we present our studies into the reactivity of electrochemically in situ generated HC(O)O with organic substrates. Reactions with benzene and a selection of substituted derivatives showed that HC(O)O is mildly electrophilic according to both experimentally and computationally derived Hammett linear free energy relationships. The reactions of HC(O)O with terminal alkenes significantly favor anti-Markovnikov oxidations yielding the corresponding aldehyde as the major product as well as further oxidation products. Analysis of plausible reaction pathways using 1-hexene as a representative substrate favored the likelihood of hydrogen abstraction from the allylic C-H bond forming a hexallyl radical followed by strongly preferred further attack of a second HC(O)O radical at the C1 position. Further oxidation products are surmised to be mostly a result of two consecutive addition reactions of HC(O)O to the CC double bond. An outer-sphere electron transfer between the formyloxyl radical donor and the [CoIIIW12O40]5- polyanion acceptor forming a donor-acceptor [D+-A-] complex is proposed to induce the observed anti-Markovnikov selectivity. Finally, the overall reactivity of HC(O)O towards hydrogen abstraction was evaluated using additional substrates. Alkanes were only slightly reactive, while the reactions of alkylarenes showed that aromatic substitution on the ring competes with C-H bond activation at the benzylic position. C-H bonds with bond dissociation energies (BDE) ≤ 85 kcal mol-1 are easily attacked by HC(O)O and reactivity appears to be significant for C-H bonds with a BDE of up to 90 kcal mol-1. In summary, this research identifies the reactivity of HC(O)O towards radical electrophilic substitution of arenes, anti-Markovnikov type oxidation of terminal alkenes, and indirectly defines the activity of HC(O)O towards C-H bond activation.
- Iron, Mark A.,Khenkin, Alexander M.,Neumann, Ronny,Somekh, Miriam
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p. 11584 - 11591
(2020/11/23)
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- A Cp-based Molybdenum Catalyst for the Deoxydehydration of Biomass-derived Diols
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Dioxo-molybdenum complexes have been reported as catalysts for the deoxydehydration (DODH) of diols and polyols. Here, we report on the DODH of diols using [Cp*MoO2]2O as catalyst (Cp*=1,2,3,4,5-pentamethylcyclopentadienyl). The DODH reaction was optimized using 2 mol % of [Cp*MoO2]2O, 1.1 equiv. of PPh3 as reductant, and anisole as solvent. Aliphatic vicinal diols are converted to the corresponding olefins by [Cp*MoO2]2O in up to 65 % yield (representing over 30 turnovers per catalyst) and 91 % olefin selectivity, which rivals the performance of other Mo-based DODH catalysts. Remarkably, cis-1,2-cyclohexanediol, which is known as quite a challenging substrate for DODH catalysis, is converted to 30 % of 1-cyclohexene under optimized reaction conditions. Overall, the mass balances (up to 79 %) and TONs per Mo achievable with [Cp*MoO2]2O are amongst the highest reported for molecular Mo-based DODH catalysts. A number of experiments aimed at providing insight in the reaction mechanism of [Cp*MoO2]2O have led to the proposal of a catalytic pathway in which the [Cp*MoO2]2O catalyst reacts with the diol substrate to form a putative nonsymmetric dimeric diolate species, which is reduced in the next step at only one of its Mo-centers before extrusion of the olefin product.
- Li, Jing,Lutz, Martin,Klein Gebbink, Robertus J. M.
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p. 6356 - 6365
(2020/11/30)
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- Non oxidative and oxidative dehydrogenation of: N -octane using FePO4: Effect of different FePO4phases on the product selectivity
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The activation of n-octane with O2 has been investigated over different phases of FePO4 which were formed under dehydrogenation and oxidative dehydrogenation (ODH) conditions. Catalytic reactions were done with the tridymite-like FePO4 catalyst which showed a high selectivity towards cracked products and carbon oxides. Under dehydrogenation conditions, tridymite phase FePO4 is transformed into the iron pyrophosphate phase (Fe2P2O7). Octenes, aromatics, C8 oxygenates, carbon oxides (COx) and cracked products were present in the product stream. The iron pyrophosphate phase, under oxidative dehydrogenation conditions, showed high selectivity towards cracked products and on regeneration (restoring of the catalytic activity) with molecular oxygen it transformed into the α-phase and quartz type phase. The regenerated catalyst (α-phase and quartz type phase) exhibited a higher selectivity to ODH products when compared to the fresh and deactivated (Fe2P2O7) catalysts. The transformation of both fresh and deactivated catalysts was evident at a temperature of 450 °C. Since the α-phase is the active phase under ODH conditions and transformations between the reduced and α-phase take place reversibly, this could explain the highest selectivity towards octenes within this temperature range. Fresh and regenerated catalysts showed steady state conversions with time under constant conditions, showing that phase transformations were mainly due to varying temperature and oxidative environment. Characterization results show that FePO4 contains fivefold coordinate Fe3+ in the regenerated and fresh catalysts, and this species is believed to be responsible for selective n-octane activation. The surface area, acidity and metal dispersion of the deactivated and regenerated catalyst showed lower values when compared to the fresh catalysts. The results obtained from M?ssbauer spectroscopy showed direct correlation with the XRD data as well as the TPR-TPO results in terms of the phase changes and oxidation state of the calcined, uncalcined, reduced and reoxidised catalyst. This journal is
- Bharuth-Ram, K.,Dasireddy, Venkata D. B. C.,Friedrich, Holger B.,Khan, Faiza B.,Singh, Sooboo
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p. 7591 - 7600
(2020/12/01)
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- Highly productive α-alkylation of ketones with alcohols mediated by an Ir-oxalamidato/solid base catalyst system
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An Ir-oxalamidato complex in combination with a solid base (e.g., magnesium aluminometasilicate/Ca(OH)2) significantly improved the catalyst productivity in α-alkylation of methyl ketones with primary alcohols. Optimization through systematic variation of the oxalamidato ligand led to a practical turnover number (TON) of 10 000.40 000.
- Maeda, Hironori,Nara, Hideki,Shimizu, Hideo
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supporting information
p. 2772 - 2779
(2020/12/29)
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- Atmospheric hydrogenation of Α Β-unsaturated ketones catalyzed by highly efficient and recyclable Pd nanocatalyst
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A thermoregulated phase-transfer Pd nanocatalyst was explored firstly and shown to be highly efficient and recyclable in the atmospheric hydrogenation of α β-unsaturated ketones. Under optimized reaction conditions, the conversion of chalcone and the selectivity of dihydrochalcone were 99% and 98%, respectively. The catalyst can be easily separated from the product and used directly for four times without evident loss in activity and selectivity. The turnover frequency (TOF) for the atmospheric hydrogenation of chalcone was 870 h?1, which to the best of our knowledge was the highest value ever reported among transition metal nanocatalysts.
- Chen, Pu,Li, Wenjiang,Wang, Yanhua
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- New molybdenum(II) complexes with α-diimine ligands: Synthesis, structure, and catalytic activity in olefin epoxidation
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Three new complexes [Mo(η3-C3H5)Br(CO)2{iPrN=C(R)C5H4N}], where R = H (IMP = N-isopropyl 2-iminomethylpyridine), Me, and Ph, were synthesized and characterized, and were fluxional in solution. The most interesting feature was the presence, in the crystal structure of the IMP derivative, of the two main isomers (allyl and carbonyls exo), namely the equatorial isomer with the Br trans to the allyl and the equatorial with the Br trans to one carbonyl, the position trans to the allyl being occupied by the imine nitrogen atom. For the R = Me complex, the less common axial isomer was observed in the crystal. These complexes were immobilized in MCM-41 (MCM), following functionalization of the diimine ligands with Si(OEt)3, in order to study the catalytic activity in olefin epoxidation of similar complexes as homogeneous and heterogeneous catalysts. FTIR,13C- and29Si-NMR, elemental analysis, and adsorption isotherms showed that the complexes were covalently bound to the MCM walls. The epoxidation activity was very good in both catalysts for the cis-cyclooctene and cis-hex-3-en-1-ol, but modest for the other substrates tested, and no relevant differences were found between the complexes and the Mo-containing materials as catalysts.
- Vasconcellos-Dias, Maria,Marreiros, Jo?o,Sales, Rita,Félix, Vitor,Brand?o, Paula,Nunes, Carla D.,José Calhorda, Maria
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- Catalytic epoxidation using dioxidomolybdenum(VI) complexes with tridentate aminoalcohol phenol ligands
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Reaction of the tridentate aminoalcohol phenol ligands 2,4-di-tert-butyl-6-(((2 hydroxyethyl)(methyl)amino)methyl)phenol (H2L1) and 2,4-di-tert-butyl-6-(((1-hydroxybutan-2-yl)amino)methyl)phenol (H2L2) with [MoO2(acac)2] in methanol solutions resulted in the formation of [MoO2(L1)(MeOH)] (1) and [MoO2(L2)(MeOH)] (3), respectively. In contrast, the analogous reactions in acetonitrile afforded the dinuclear complexes [Mo2O2(μ-O)2(L1)2] (2) and [Mo2O2(μ-O)2(L2)2] (4). The corresponding reactions with the potentially tetradentate ligand 3-((3,5-di-tert-butyl-2-hydroxybenzyl)(methyl)amino)propane-1,2-diol (H3L3) led to the formation of the mononuclear complex [MoO2(L3)(MeOH)] (5) in methanol while in acetonitrile solution a trinuclear structure [Mo3O3(μ-O)3(L3)3] (6) was obtained. In both cases, the ligand moiety L3 coordinated in a tridentate fashion. The catalytic activities of complexes 1–6 in epoxidation of five different olefins, S1-5, with tert-butyl hydroperoxide and hydrogen peroxide were studied. The catalytic activities were found to be moderate to good for the reaction of substrate cis-cyclooctene S1, while all complexes were less active in the epoxidation of the more challenging substrates S2-5. The molecular structures of 1, 2, 4 and 6 were determined by single crystal X-ray diffraction analyses.
- Hossain, Md. Kamal,Schachner, J?rg A.,Haukka, Matti,M?sch-Zanetti, Nadia C.,Nordlander, Ebbe,Lehtonen, Ari
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- Catalytic performance of bulk and colloidal Co/Al layered double hydroxide with Au nanoparticles in aerobic olefin oxidation
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A Co/Al layered double hydroxide material was synthesized in both bulk and exfoliated (colloidal) forms. Anion exchange with methionine allowed immobilization of Au nanoparticles previously prepared by a biomimetic method using an anti-oxidant tea aqueous extract to reduce the Au salt solution. The catalytic performance of bulk and exfoliated clays Au-hybrid materials was assessed in aerobic olefin epoxidation. Both catalysts were very active towards the epoxide products and with very interesting substrate conversion levels after 80 h reaction time. The Au-exfoliated material, where the nanosheets work as large ligands, yielded higher product stereoselectivity in the case of limonene epoxidation. This arises from a confined environment around the Au nanoparticles wrapped by the clay nanosheets modulating access to the catalytic active centres by reagents. Mechanistic assessment was also accomplished for styrene oxidation by DFT methods.
- Leandro, Sónia R.,Fernandes, Cristina I.,Viana,Mourato,Vaz, Pedro D.,Nunes, Carla D.
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- In Vitro and in Vivo One-Pot Deracemization of Chiral Amines by Reaction Pathway Control of Enantiocomplementary ω-Transaminases
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Biocatalytic cascade conversion of racemic amines into optically pure ones using enantiocomplementary ω-transaminases (ω-TAs) has been developed by thermodynamic and kinetic control of reaction pathways where 12 competing reactions occur with pyruvate and isopropylamine used as cosubstrates. Thermodynamic control was achieved under reduced pressure for selective removal of a coproduct (i.e., acetone), leading to elimination of six undesirable reactions. Engineered orthogonality in substrate specificities of ω-TAs was exploited for kinetic control, enabling suppression of four additional reactions. Taken together, the net reaction pathway could be directed to two desired reactions (i.e., oxidative deamination of R-amine and reductive amination of the resulting ketone into antipode S-amine). This strategy afforded one-pot deracemization of various chiral amines with >99% eeS and 85-99% reaction yields of the resulting S-amine products. The in vitro cascade reaction could be successfully implemented in a live microbe using glucose or l-threonine as a cheap amino acceptor precursor, demonstrating a synthetic metabolic pathway enabling deracemization of chiral amines which has never been observed in living organisms.
- Han, Sang-Woo,Jang, Youngho,Shin, Jong-Shik
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supporting information
p. 6945 - 6954
(2019/08/26)
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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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- Efficient Palladium(0) supported on reduced graphene oxide for selective oxidation of olefins using graphene oxide as a ‘solid weak acid’
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Selective oxidation of olefin derivatives to ketones has made innovative development over palladium(0) supported on reduced graphene oxide. Compared to traditional Wacker oxidation, the novel method offers an economical and environment-friendly option by using graphene oxide (GO) as a ‘solid weak acid’ instead of classical homogeneous catalysts like H2SO4 and CF3COOH. X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscope and transmission electron microscopy images of Pd0/RGO showed that the nanoscaled Pd particles generated at the flake structure of reduced graphene oxide. Under optimized condition, up to 44 kinds of ketones with different structures can be prepared with excellent yields.
- Gao, Xi,Zhou, Jianhao,Peng, Xinhua
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- Asymmetric Enzymatic Hydration of Unactivated, Aliphatic Alkenes
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The direct enantioselective addition of water to unactivated alkenes could simplify the synthesis of chiral alcohols and solve a long-standing challenge in catalysis. Here we report that an engineered fatty acid hydratase can catalyze the asymmetric hydration of various terminal and internal alkenes. In the presence of a carboxylic acid decoy molecule for activation of the oleate hydratase from E. meningoseptica, asymmetric hydration of unactivated alkenes was achieved with up to 93 % conversion, excellent selectivity (>99 % ee, >95 % regioselectivity), and on a preparative scale.
- Demming, Rebecca M.,Hammer, Stephan C.,Nestl, Bettina M.,Gergel, Sebastian,Fademrecht, Silvia,Pleiss, Jürgen,Hauer, Bernhard
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supporting information
p. 173 - 177
(2018/12/11)
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- A step forward in solvent knitting strategies: Ruthenium and gold phosphine complex polymerization results in effective heterogenized catalysts
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Porous polymers based on ruthenium and gold triphenylphosphine complexes (KPhos(Ru), KPhos(Ru)Bi, KPhos(AuCl) and KPhos(AuNTf2)) were prepared via a cost-effective solvent knitting method with [RuHClCO(PPh3)3] or AuXPPh3 (X = Cl, NTf2) as single monomers or combined with biphenyl, which represents a further approach to obtain heterogenized catalysts. The resulting materials mainly preserve the metal coordination environment of their parent complexes, are stable up to 350 °C and have reasonable surface areas (250-300 m2 g-1 for KPhos(Ru)-polymers). KPhos(Ru)s selectively catalyze the imination of alcohols in the presence of base and the results for KPhos(Au)s show they are effective for the intermolecular hydration and hydroamination of alkynes. These materials can be reused several times without significant loss of activity. This novel and simple method affords heterogenized catalysts that combine the reactivity and selectivity of their homogeneous counterparts with the stability and reusability of a heterogeneous framework.
- Valverde-González, Antonio,Marchal, Gwendoline,Maya, Eva M.,Iglesias, Marta
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p. 4552 - 4560
(2019/09/09)
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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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- Redetermination of the Structure of a Water-Soluble Hypervalent Iodine(V) Reagent AIBX and Its Synthetic Utility in the Oxidation of Alcohols and Synthesis of Isoxazoline N-Oxides
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The structure of a water-soluble hypervalent iodine(V) reagent AIBX is re-examined through its single-crystal X-ray analysis and theoretical calculations including Mayer bond order and localized orbital locator (LOL) and AIBX is believed to be a pseudocyclic iodylarene because of the strong electron-withdrawing nature of the trimethylammonium cation on its phenyl ring, which would decrease the electron density of carboxylic anion and make the ortho-carboxyl oxygen anion incapable to form hypervalent bond with iodine atom. However, the cyclic benziodoxole structure of AIBX could be obtained by adding a Br?nsted acid, which was supported by the calculation result including the increase of Mayer bond order and the shortening of the I-O bond length. Moreover, the fact that the system of AIBX and TFA could oxidize various alcohols to their corresponding carbonyl compounds would indicate that AIBX constitutes a cyclic benziodoxole structure under acidic conditions. In addition, an efficient method has been developed for the synthesis of isoxazoline N-oxides via AIBX-induced dehydrogenative cyclization using β-keto esters as substrates and methyl nitroacetate as a nucleophile.
- Shen, Hui-Jie,Duan, Ya-Nan,Zheng, Ke,Zhang, Chi
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p. 14381 - 14393
(2019/11/13)
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- Catalytic Oxidation of Alcohols Using a 2,2,6,6-Tetramethylpiperidine-N-hydroxyammonium Cation
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The oxidation of alcohols to aldehydes, ketones, and carboxylic acids is reported using 2,2,6,6-tetramethylpiperidine-4-acetamido-hydroxyammonium tetrafluoroborate as a catalyst in conjunction with sodium hypochlorite pentahydrate as a terminal oxidant. The reaction is generally complete within 30–120 min using an acetonitrile/water mix as the solvent, and no additives are required. Product yields are good to excellent and of particular note is that the methodology can be used to access aryl α-trifluoromethyl ketones.
- Miller, Shelli A.,Bisset, Kathryn A.,Leadbeater, Nicholas E.,Eddy, Nicholas A.
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supporting information
p. 1413 - 1417
(2019/01/04)
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- Extended Open-Chain Polyenides as Versatile Delocalized Anion Ligands for Metal Chain Clusters
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Although small cyclic- and open-chain unsaturated hydrocarbon anions such as cyclopentadienide and open-chain pentadienide are used as the strongly electron-donating auxiliary ligands for metal complexes, more extended π-conjugated unsaturated hydrocarbon
- Yamashita, Mitsuki,Kawasumi, Yuna,Tachibana, Yuki,Horiuchi, Shinnosuke,Yamamoto, Koji,Murahashi, Tetsuro
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supporting information
p. 1212 - 1216
(2019/01/04)
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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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- 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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- Synthesis, structural characterization and C–H activation property of a tetra-iron(III) cluster
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A non-heme tetra-iron cluster, [Fe4 III(μ-O)2(μ-OAc)6(2,2′-bpy)2(H2O)2](NO3 ?)(OH?) (1), [OAc = acetate; 2,2′-bpy = 2,2′-bipyridine] containing oxido- and acetato-bridges was synthesized and structurally characterized by different spectroscopic methods including single crystal X-ray diffraction studies. X-ray crystal structure analysis of 1 revealed that tetra-iron complex was crystallized in monoclinic system with C2/c space group. Each of the Fe centres in 1 was found to exist in octahedral geometry and interconnected by oxido- and acetato-bridges. Bond valence sum (BVS) calculation recommended the existence of iron centres in +3 oxidation state. Variable temperature magnetic measurement authenticated the dominating antiferromagnetic ordering among the iron centres in the solid state of 1. This tetra-iron cluster was also evaluated as an efficient catalytic system towards the oxidation of both linear & cyclic alkanes without production of primary C–H bond oxidation products. Oxidation of secondary C–H bonds attested the formation of both the corresponding alcohols & ketones in 27–900 TONs. The tetra-iron catalytic system with Alcohol/Ketone values 0.2–1.7 indicated the involvement of freely diffusing carbon-centered radicals rather than metal based oxidant.
- Dey, Dhananjay,Patra, Moumita,Al-Hunaiti, Afnan,Yadav, Hare Ram,Al-mherat, Afrah,Arar, Sharif,Maji, Milan,Choudhury, Angshuman Roy,Biswas, Bhaskar
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p. 220 - 226
(2019/01/05)
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- Palladium-Catalyzed Aerobic Anti-Markovnikov Oxidation of Aliphatic Alkenes to Terminal Acetals
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Terminal acetals were selectively synthesized from various unbiased aliphatic terminal alkenes and 1,2-, 1,3-, or 1,4-diols using a PdCl2(MeCN)2/CuCl catalyst system in the presence of p-toluquinone under 1 atm of O2 and mild reaction conditions. The slow addition of terminal alkenes suppressed the isomerization to internal alkenes successfully. Electron-deficient cyclic alkenes, such as p-toluquinone, were key additives to enhance the catalytic activity and the anti-Markovnikov selectivity. The halogen groups in the alkenes were found to operate as directing groups, suppressing isomerization and increasing the selectivity efficiently.
- Komori, Saki,Yamaguchi, Yoshiko,Kataoka, Yasutaka,Ura, Yasuyuki
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p. 3093 - 3099
(2019/03/29)
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- Efficient synthesis of enantiopure amines from alcohols using resting: E. coli cells and ammonia
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α-Chiral amines are pivotal building blocks for chemical manufacturing. Stereoselective amination of alcohols is receiving increased interest due to its higher atom-efficiency and overall improved environmental footprint compared with other chemocatalytic and biocatalytic methods. We previously developed a hydrogen-borrowing amination by combining an alcohol dehydrogenase (ADH) with an amine dehydrogenase (AmDH) in vitro. Herein, we implemented the ADH-AmDH bioamination in resting Escherichia coli cells for the first time. Different genetic constructs were created and tested in order to obtain balanced expression levels of the dehydrogenase enzymes in E. coli. Using the optimized constructs, the influence of several parameters towards the productivity of the system were investigated such as the intracellular NAD+/NADH redox balance, the cell loading, the survival rate of recombinant E. coli cells, the possible toxicity of the components of the reaction at different concentrations and the influence of different substrates and cosolvents. In particular, the cofactor redox-balance for the bioamination was maintained by the addition of moderate and precise amounts of glucose. Higher concentrations of certain amine products resulted in toxicity and cell death, which could be alleviated by the addition of a co-solvent. Notably, amine formation was consistent using several independently grown E. coli batches. The optimized E. coli/ADH-AmDH strains produced enantiopure amines from the alcohols with up to 80% conversion and a molar productivity up to 15 mM. Practical applicability was demonstrated in a gram-scale biotransformation. In summary, the present E. coli-ADH-AmDH system represents an important advancement towards the development of 'green', efficient and selective biocatalytic processes for the amination of alcohols.
- Houwman, Joseline A.,Knaus, Tanja,Costa, Magda,Mutti, Francesco G.
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supporting information
p. 3846 - 3857
(2019/07/31)
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- Mild Chemoenzymatic Oxidation of Allylic sec-Alcohols. Application to Biocatalytic Stereoselective Redox Isomerizations
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The design of catalytic oxidative methodologies in aqueous medium under mild reaction conditions and using molecular oxygen as final electron acceptor represents a suitable alternative to the traditional oxidative transformations. These methods are especially relevant if other functionalities that can be oxidized are present within the same molecule, as in the case of allylic alcohols. Herein we apply a simple chemoenzymatic system composed of the laccase from Trametes versicolor and 2,2,6,6-tetramethylpiperidinyloxy radical (TEMPO) to oxidize a series of racemic allylic sec-alcohols into the corresponding α,β-unsaturated ketones. Afterward, these compounds react with different commercially available ene-reductases to afford the corresponding saturated ketones. Remarkably, in the case of trisubstituted alkenes, the bioreduction reaction occurred with high stereoselectivity. Overall, a bienzymatic one-pot two-step sequential strategy has been described with respect to the synthesis of saturated ketones starting from racemic allylic alcohols, thus resembling the metal-catalyzed redox isomerizations of these derivatives that have been previously reported in the literature.
- Martínez-Montero, Lía,Gotor, Vicente,Gotor-Fernández, Vicente,Lavandera, Iván
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p. 2413 - 2419
(2018/03/13)
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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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