- Detection of H2, HD, and D2 by Raman Spectroscopy: A Powerful Aid for the Elucidation of Reaction Mechanisms
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The detection of H2, HD, and D2 by gas-phase Raman spectroscopy has shown that the photochemical and thermal dehydrogenation of dioxabicycloalkanes occurs by an intramolecular process.The general applicability of the Raman technique for the identification of dihydrogen produced in the course of a reaction is based upon the high-scattering cross section of dihydrogen, which allows the ready detection of submicromolar quantities of the gas.
- Best, Stephen P.,Bloodworth, A. J.,Clark, Robin J. H.,Eggelte, Henny J.
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Read Online
- An aerobic oxidation of alcohols into carbonyl synthons using bipyridyl-cinchona based palladium catalyst
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We have reported an aerobic oxidation of primary and secondary alcohols to respective aldehydes and ketones using a bipyridyl-cinchona alkaloid based palladium catalytic system (PdAc-5) using oxygen at moderate pressure. ThePdAc-5catalyst was analysed using SEM, EDAX, and XPS analysis. The above catalytic system is used in experiments for different oxidation systems which include different solvents, additives, and bases which are cheap, robust, non-toxic, and commercially available on the industrial bench. The obtained products are quite appreciable in both yield and selectivity (70-85%). In addition, numerous important studies, such as comparisons with various commercial catalysts, solvent systems, mixture of solvents, and catalyst mole%, were conducted usingPdAc-5. The synthetic strategy of oxidation of alcohol into carbonyl compounds was well established and all the products were analysed using1H NMR,13CNMR and GC-mass analyses.
- Cheedarala, Ravi Kumar,Chidambaram, Ramasamy R.,Siva, Ayyanar,Song, Jung Il
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p. 32942 - 32954
(2021/12/02)
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- Hydrolysis process of dimethyl succinylsuccinate
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The invention discloses a hydrolysis process of dimethyl succinylsuccinate, which is specifically implemented according to the following steps: step 1, adding DMSS into a reaction kettle, adding a certain amount of water, and starting stirring; 2, adding a phase transfer catalyst into the reaction kettle, and starting heating; and 3, after the temperature is increased to the reaction temperature, adding an acid and a transition metal salt, and starting a hydrolysis reaction. According to the hydrolysis process of dimethyl succinylsuccinate, the problems that DMSS is difficult to hydrolyze and hydrolysis time is long in the prior art are solved.
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Paragraph 0030-0045
(2021/04/21)
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- Identification of key oxidative intermediates and the function of chromium dopants in PKU-8: catalytic dehydrogenation ofsec-alcohols withtert-butylhydroperoxide
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Catalytic oxidation reaction using green oxidants plays an important role in modern chemical engineering; however, thein situgenerated active species and the related catalytic mechanism need to be understood in depth. For this purpose, Cr-substituted aluminoborate Cr-PKU-8 catalysts were synthesized and applied as recyclable heterogeneous catalysts for the oxidation of aliphatic and aromatic alcohols usingtert-butylhydroperoxide (TBHP). Both high efficiency and selectivity (>99%) were achieved during the dehydrogenation of varioussec-alcohols into acetone in H2O solvent medium. From the analyses using isotopic tracer, molecular probe and cyclic voltammetry strategies, the chromium ions were observed to undergo a Cr3+-Cr2+-Cr3+redox cycle. DFT calculations suggest thatt-BuOO* is more energetically favourable for hydrogen abstraction fromsec-alcohol thant-BuO*, and probably acts as the key active species. Accordingly, the reaction scheme was proposed to interpret the catalytic process based on the observed results.
- Wang, Weilu,He, Yang,He, Junkai,Dang, Yanliu,Kankanmkapuge, Tharindu,Gao, Wenliang,Cong, Rihong,Suib, Steven L.,Yang, Tao
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p. 1365 - 1374
(2021/03/14)
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- Reductive Electrochemical Activation of Molecular Oxygen Catalyzed by an Iron-Tungstate Oxide Capsule: Reactivity Studies Consistent with Compound i Type Oxidants
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The reductive activation of molecular oxygen catalyzed by iron-based enzymes toward its use as an oxygen donor is paradigmatic for oxygen transfer reactions in nature. Mechanistic studies on these enzymes and related biomimetic coordination compounds designed to form reactive intermediates, almost invariably using various "shunt" pathways, have shown that high-valent Fe(V)=O and the formally isoelectronic Fe(IV) =O porphyrin cation radical intermediates are often thought to be the active species in alkane and arene hydroxylation and alkene epoxidation reactions. Although this four decade long research effort has yielded a massive amount of spectroscopic data, reactivity studies, and a detailed, but still incomplete, mechanistic understanding, the actual reductive activation of molecular oxygen coupled with efficient catalytic transformations has rarely been experimentally studied. Recently, we found that a completely inorganic iron-tungsten oxide capsule with a keplerate structure, noted as {Fe30W72}, is an effective electrocatalyst for the cathodic activation of molecular oxygen in water leading to the oxidation of light alkanes and alkenes. The present report deals with extensive reactivity studies of these {Fe30W72} electrocatalytic reactions showing (1) arene hydroxylation including kinetic isotope effects and migration of the ipso substituent to the adjacent carbon atom ("NIH shift"); (2) a high kinetic isotope effect for alkyl C - H bond activation; (3) dealkylation of alkylamines and alkylsulfides; (4) desaturation reactions; (5) retention of stereochemistry in cis-alkene epoxidation; and (6) unusual regioselectivity in the oxidation of cyclic and acyclic ketones, alcohols, and carboxylic acids where reactivity is not correlated to the bond disassociation energy; the regioselectivity obtained is attributable to polar effects and/or entropic contributions. Collectively these results also support the conclusion that the active intermediate species formed in the catalytic cycle is consistent with a compound I type oxidant. The activity of {Fe30W72} in cathodic aerobic oxidation reactions shows it to be an inorganic functional analogue of iron-based monooxygenases.
- Bugnola, Marco,Shen, Kaiji,Haviv, Eynat,Neumann, Ronny
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p. 4227 - 4237
(2020/05/05)
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- Photoinduced Reactivity in a Dispiro-1,2,4-trioxolane: Adamantane Ring Expansion and First Direct Observation of the Long-Lived Triplet Diradical Intermediates
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Dispiro-1,2,4-trioxolane, 1, an ozonide with efficient and broad antiparasitic activity, was synthesized and investigated using matrix isolation FTIR and EPR spectroscopies together with both B3LYP/6-311++G(3df,3dp) and M06-2X/6-311++G(3df,3dp) theoretical methods. Irradiations (λ ≥ 290 nm) of the matrix isolated 1 (Ar or N2) afforded exclusively 4-oxahomoadamantan-5-one, 4, and 1,4-cyclohexanedione, 5. These results suggested that the reaction proceeded via a dioxygen-centered diradical intermediate, formed upon homolytic cleavage of the labile peroxide bond, which regioselectively isomerized to form the more stable (secondary carbon-centered)/oxygen-centered diradical. In situ EPR measurements during the photolysis of 1 deposited in a MeTHF-matrix led to the detection of signals corresponding to two triplet species, one of which was short-lived while the other proved to be persistent at 10 K. These observations strongly support the proposed mechanism for the photogeneration of 4 and 5, which involves intramolecular rearrangement of the intermediate diradical species 2 to afford the triplet diradical 3.
- Brás, Elisa M.,Cabral, Lília I. L.,Amado, Patrícia S. M.,Abe, Manabu,Cristiano, Maria L. S.,Fausto, Rui
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p. 4202 - 4210
(2020/06/27)
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- Chemoselective transfer hydrogenation of Α,Β-unsaturated carbonyls catalyzed by a reusable supported Pd nanoparticles on biomass-derived carbon
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We herein report highly chemoselective transfer hydrogenation of α,β-unsaturated carbonyl compounds to saturated carbonyls with formic acid as a hydrogen donor over a stable and recyclable heterogeneous Pd nanoparticles (NPs) on N,O-dual doped hierarchical porous biomass-derived carbon. The synergistic effect between Pd NPs and incorporated heteroatoms on carbon plays a critical role on promoting the reaction efficiency. A series of α,β-aromatic and aliphatic unsaturated carbonyl compounds was selectively reduced to their corresponding saturated carbonyls in up to 97% isolated yields with good tolerance of various functional groups. In addition, the catalyst can be successively reused for at least 6 times without significant loss in reaction efficiency.
- Song, Tao,Duan, Yanan,Yang, Yong
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- Chemoselective Hydrogenation of α,β-Unsaturated Carbonyls Catalyzed by Biomass-Derived Cobalt Nanoparticles in Water
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Herein, we report highly chemoselective hydrogenation of α,β-unsaturated carbonyls to saturated carbonyls catalyzed by cobalt nanoparticles supported on the biomass-derived carbon from bamboo shoots with molecular hydrogen in water, which is the first prototype using a heterogeneous non-noble metal catalyst for such organic transformation as far as we know. The optimal cobalt nanocatalyst, CoOx@NC-800, manifested remarkable activity and selectivity for hydrogenation of C=C in α,β-unsaturated carbonyls under mild conditions. A broad set of α,β-aromatic and aliphatic unsaturated carbonyls were selectively reduced to their corresponding saturated carbonyls in up to 99 % yields with good tolerance of various functional groups. Meanwhile, a new straightforward one-pot cascade synthesis of saturated carbonyls was realized with high activity and selectivity via the cross-aldol condensation of ketones with aldehydes followed by selective hydrogenation. More importantly, this one-pot strategy is applicable for the expedient synthesis of Loureirin A, a versatile bioactive and medicinal molecule, from readily available starting materials, further highlighting the practical utility of the catalyst. In addition, the catalyst can be easily separated for successive reuses without significant loss in both activity and selectivity.
- Song, Tao,Ma, Zhiming,Yang, Yong
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p. 1313 - 1319
(2019/01/25)
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- Selective C(sp3)?H Aerobic Oxidation Enabled by Decatungstate Photocatalysis in Flow
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A mild and selective C(sp3)?H aerobic oxidation enabled by decatungstate photocatalysis has been developed. The reaction can be significantly improved in a microflow reactor enabling the safe use of oxygen and enhanced irradiation of the reaction mixture. Our method allows for the oxidation of both activated and unactivated C?H bonds (30 examples). The ability to selectively oxidize natural scaffolds, such as (?)-ambroxide, pregnenolone acetate, (+)-sclareolide, and artemisinin, exemplifies the utility of this new method.
- Laudadio, Gabriele,Govaerts, Sebastian,Wang, Ying,Ravelli, Davide,Koolman, Hannes F.,Fagnoni, Maurizio,Djuric, Stevan W.,No?l, Timothy
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supporting information
p. 4078 - 4082
(2018/03/21)
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- Rh nanoparticles from thiolate dimers: Selective and reusable hydrogenation catalysts in ionic liquids
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Thiolate-capped rhodium nanoparticles were synthesized by decomposition of the organometallic precursors [Rh(μ-SC12H25)(COD)]2 (I) and [Rh(μ-SC6H11)(COD)]2 (II) under hydrogen pressure, in imidazolium-based ionic liquids and organic solvent, without the external addition of ligands as stabilizers and were compared to RhNPs synthesized from [Rh(μ-OMe)(COD)]2. The use of ionic liquids during the synthesis of rhodium nanoparticles resulted in homogeneously well-dispersed systems as observed by TEM, where the thiolate ligand remains intact as demonstrated by XPS analysis and gas chromatography. The thiolate-capped rhodium nanoparticles generated from II were active catalysts in hydrogenation reactions with high selectivity towards alkene, nitro and imine groups. The absence of thiolate ligand generated very active catalytic systems and the hydrogenation of carbonyl groups was possible. The effect of thiol stabilizer was studied in the reductive N-alkylation to produce N-benzylaniline through one pot synthesis from benzaldehyde and nitrobenzene, where only the thiolate-capped RhNPs showed complete conversion and high selectivity. Additionally, the thiolate-capped RhNPs permitted the reuse of the catalytic systems for ten catalytic cycles for selected hydrogenation reactions after product separation.
- Serrano-Maldonado,Rozenel,Jimenez-Santiago,Guerrero-Ríos,Martin
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p. 4373 - 4382
(2018/09/11)
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- FeCl3·6H2O/acetaldehyde, a versatile system for the deprotection of ketals and acetals via a transacetalization process
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Mild and efficient catalytic deprotection of ketals/acetals mediated by FeCl3·6H2O/acetaldehyde has been described in this paper. The versatility and high chemoselectivity of the iron(iii)/aldehyde system are demonstrated by a large scope of examples. Deprotected ketones/aldehydes are nearly quantitatively isolated after filtration over a pad of silica gel followed by evaporation of volatile by-products.
- Schiavo, Lucie,Jeanmart, Lo?c,Lanners, Steve,Choppin, Sabine,Hanquet, Gilles
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p. 1421 - 1424
(2017/02/23)
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- NMR spectroscopic conformational analysis of 4‐methylene‐ cyclohexyl pivalate—the effect of sp2 hybridization
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The conformational equilibrium of the axial/equatorial conformers of 4‐methylene ‐cyclohexyl pivalate is studied by dynamic NMR spectroscopy in a methylene chloride/freon mixture. At 153 K, the ring interconversion gets slow on the nuclear magnetic resonance timescale, the conformational equilibrium (?ΔG°) can be examined, and the barrier to ring interconversion (ΔG#) can be determined. The structural influence of sp2 hybridization on both ΔG° and ΔG#of the cyclohexyl moiety can be quantified.
- Kleinpeter, Erich,Heydenreich, Matthias,Koch, Andreas,Krtitschka, Angela,Krüger, Tobias,Linker, Torsten
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p. 1073 - 1078
(2018/04/10)
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- Oxidation of Secondary Methyl Ethers to Ketones
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We present a mild way of converting secondary methyl ethers into ketones using calcium hypochlorite in aqueous acetonitrile with acetic acid as activator. The reaction is compatible with various oxygen- and nitrogen-containing functional groups and afforded the corresponding ketones in up to 98% yield. The use of this methodology could expand the application of the methyl group as a useful protecting group.
- Gilissen, Pieter J.,Blanco-Ania, Daniel,Rutjes, Floris P. J. T.
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p. 6671 - 6679
(2017/07/15)
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- Copper(II) and cobalt(II) tetrazole-saccharinate complexes as effective catalysts for oxidation of secondary alcohols
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Mononuclear Cu(II) and Co(II) complexes comprising 2-methyltetrazole-saccharinate bidentate N,N-chelating ligand have been synthesized for the first time and tested as homogeneous catalysts for oxidation of secondary alcohols in a solvent-free and microwave assisted protocol using aqueous tert-butyl hydroperoxide (TBHP) as oxidant. The developed catalytic system exhibits broad functional group compatibility, allowing efficient and selective conversion of a variety of secondary alcohols, including allylic ones, into the corresponding ketones. With typical 0.2 mol% content of the catalyst and under 20–50 W microwave irradiation, most reactions are complete within 10 min, presenting TONs up to 5.5 × 102 and TOFs up to 1.1 × 104 h?1. No additives and co-oxidants have been used, while TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxyl) acts as inhibitor in most cases. A plausible reaction mechanism involving the new catalytic systems is outlined.
- Frija, Luís M.T.,Alegria, Elisabete C.B.A.,Sutradhar, Manas,Cristiano, M. Lurdes S.,Ismael, Amin,Kopylovich, Maximilian N.,Pombeiro, Armando J.L.
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p. 283 - 290
(2016/11/04)
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- Copper(ii) and iron(iii) complexes with arylhydrazone of ethyl 2-cyanoacetate or formazan ligands as catalysts for oxidation of alcohols
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The aquasoluble [Cu(1κN,O2:2κO-HL1)(S)]2 [S = CH3OH (1), (CH3)2NCHO (2)] and [Cu(κN-HL1)(en)2]·CH3OH·H2O (3) CuII complexes were prepared by the reaction of CuII nitrate hydrate with the new ligand (E/Z)-4-(2-(1-cyano-2-ethoxy-2-oxoethylidene)hydrazinyl)-3-hydroxybenzoic acid (H3L1), in the presence (for 3) or absence (for 1 and 2) of ethylenediamine (en), while the FeIII complex [Fe(κN3-HL2)2] (4) was isolated by treatment of iron(III) chloride hexahydrate with the new ligand (1E,1E)-N′,2-di(1H-1,2,4-triazol-3-yl)diazenecarbohydrazonoyl cyanide (H3L2), and characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffraction. Cooperative E,Z → E isomerization of H3L1, induced by coordination and ionic interactions, occurs upon interaction with CuII in the presence of en. Complexes 1-4 act as catalyst precursors for the solvent-free microwave (MW) assisted selective oxidation of primary or secondary alcohols and diols to the corresponding aldehydes, ketones and diketones, respectively, with yields in the 5-99% range (TONs up to 4.96 × 102) after 60 min of MW irradiation at 120 °C. The influence of temperature, time and organic radicals was studied and also the regioselective oxidation of the catalytic systems involving the primary and secondary alcohols.
- Martins, Nuno M. R.,Mahmudov, Kamran T.,Guedes Da Silva, M. Fátima C.,Martins, Luísa M. D. R. S.,Pombeiro, Armando J. L.
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supporting information
p. 10071 - 10083
(2016/12/07)
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- Greener selective cycloalkane oxidations with hydrogen peroxide catalyzed by copper-5-(4-pyridyl)tetrazolate metal-organic frameworks
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Microwave assisted synthesis of the Cu(I) compound [Cu(μ4-4-ptz)]n [1, 4-ptz = 5-(4-pyridyl)tetrazolate] has been performed by employing a relatively easy method and within a shorter period of time compared to its sister compounds. The syntheses of the Cu(II) compounds [Cu3(μ3-4-ptz)4(μ2-N3)2(DMF)2]n·(DMF)2n (2) and [Cu(μ2-4-ptz)2(H2O)2]n (3) using a similar method were reported previously by us. MOFs 1-3 revealed high catalytic activity toward oxidation of cyclic alkanes (cyclopentane, -hexane and -octane) with aqueous hydrogen peroxide, under very mild conditions (at room temperature), without any added solvent or additive. The most efficient system (2/H2O2) showed, for the oxidation of cyclohexane, a turnover number (TON) of 396 (TOF of 40 h?1), with an overall product yield (cyclohexanol and cyclohexanone) of 40% relative to the substrate. Moreover, the heterogeneous catalytic systems 1-3 allowed an easy catalyst recovery and reuse, at least for four consecutive cycles, maintaining ca. 90% of the initial high activity and concomitant high selectivity.
- Martins, Luísa,Nasani, Rajendar,Saha, Manideepa,Mobin, Shaikh,Mukhopadhyay, Suman,Pombeiro, Armando
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p. 19203 - 19220
(2015/11/27)
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- Microwave-assisted oxidation of alcohols using zinc polyoxometalate
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In the presence of 30% aqueous hydrogen peroxide and [WZn3(H2O)2][ZnW9O34)2]12- polyoxometalate as a catalyst, primary and secondary alcohols were oxidized to carboxylic acids and ketones, respectively, in short reaction times (ca. 15 min) under microwave-pressurized conditions.
- Kasprzyk, Wiktor,Galica, Mateusz,Bednarz, Szczepan,Bogda?, Dariusz
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supporting information
p. 2757 - 2760
(2015/02/02)
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- IBX works efficiently under solvent free conditions in ball milling
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IBX (2-iodoxybenzoic acid), discovered in 1893, is an oxidant in synthetic chemistry whose extensive use is impeded by its explosiveness at high temperature and poor solubility in common organic solvents except DMSO. Since the discovery of Dess-Martin Periodinane in 1983, several modified IBX systems have been reported. However, under ball milling conditions, IBX works efficiently with various organic functionalities at ambient temperature under solvent free conditions. Also, the waste IBA (2-iodosobenzoic acid) produced from the reactions was in situ oxidized to IBX in the following step using oxone and thus reused for multiple cycles by conserving its efficiency (only ～6% loss after 15 cycles). This work describes an overview of a highly economical synthetic methodology which overcomes the problems of using IBX, efficiently in gram scale and in a non-explosive way. This journal is the Partner Organisations 2014.
- Achar, Tapas Kumar,Maiti, Saikat,Mal, Prasenjit
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p. 12834 - 12839
(2014/04/03)
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- Mechanisms of selective cleavage of C-O bonds in di-aryl ethers in aqueous phase
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A route for cleaving the C-O aryl ether bonds of p-substituted H-, CH 3-, and OH- diphenyl ethers has been explored over Ni/SiO2 catalyst at very mild conditions (393 K, 0.6 MPa). The C-O bond of diphenyl ether is cleaved by parallel hydrogenolysis and hydrolysis (hydrogenolysis combined with HO* addition) on Ni. The rates as a function of H2 pressure from 0 to 10 MPa indicate that the rate-determining step is the C-O bond cleavage on Ni surface. H* atoms compete with the organic reactant for adsorption leading to a maximum in the rate with increasing H2 pressure. In contrast to diphenyl ether, hydrogenolysis is the exclusive route for cleaving a C-O bond of di-p-tolyl ether to form p-cresol and toluene. 4,4′-Dihydroxydiphenyl ether undergoes sequential surface hydrogenolysis, first to phenol and OC6H4OH * (adsorbed), which is then cleaved to phenol (C 6H4OH* with added H*) and H2O (O* with two added H*) in a second step. Density function theory supports the operation of this pathway. Notably, addition of H* to OC6H4OH * is less favorable than a further hydrogenolytic C-O bond cleavage. The TOFs of three diaryl ethers with Ni/SiO2 in water follow the order 4,4′-dihydroxydiphenyl ether 69molmolNi Surf-1h -1 > diphenyl ether 26molmolNi Surf-1h-1 > di-p-tolyl ether 1.3molmolNi Surf-1h-1, in line with the increasing apparent activation energies, ranging from 4,4′-dihydroxydiphenyl ether (93 kJ mol-1) -1) -1).
- He, Jiayue,Zhao, Chen,Mei, Donghai,Lercher, Johannes A.
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p. 280 - 290
(2014/04/03)
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- Preparation, characterization and catalytic activity of MgO/SiO2 supported vanadium oxide based catalysts
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Vanadium oxide-based catalyst obtained by grafting VOCl3 on Florisil (MgO:SiO2) with the molar ratio of 15:85 have been studied for the selective oxidation of cyclohexane in order to obtain cyclohexyl hydroperoxide, cyclohexanol and
- Aboelfetoh, Eman Fahmy,Pietschnig, Rudolf
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- Efficient cyclohexane oxidation with hydrogen peroxide catalysed by a C-scorpionate iron(II) complex immobilized on desilicated MOR zeolite
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The hydrotris(pyrazol-1-yl)methane iron(II) complex [FeCl 2{η3-HC(pz)3}] (Fe, pz = pyrazol-1-yl) immobilized on commercial (MOR) or desilicated (MOR-D) zeolite, catalyses the oxidation of cyclohexane with hydrogen peroxide to cyclohexanol and cyclohexanone, under mild conditions. MOR-D/Fe (desilicated zeolite supported [FeCl2{η3-HC(pz)3}] complex) provides an outstanding catalytic activity (TON up to 2.90 x 103) with the concomitant overall yield of 38%, and can be easy recovered and reused. The MOR or MOR-D supported hydrotris(pyrazol-1-yl)methane iron(II) complex (MOR/Fe and MOR-D/Fe, respectively) was characterized by X-ray powder diffraction, ICP-AES, and TEM studies as well as by IR spectroscopy and N2 adsorption at -196 C. The catalytic operational conditions (e.g., reaction time, type and amount of oxidant, presence of acid and type of solvent) were optimized.
- Martins,Martins,Alegria,Carvalho,Pombeiro
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- Mechanistic pathways in CF3COOH-mediated deacetalization reactions
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(Chemical Equation Presented) It has been widely accepted that both the protection of carbonyls and the deprotection of acetals and ketals involve the participation of a water molecule: formation of acetals and ketals is a dehydration process, whereas the deprotection is often referred to as hydrolysis, which, as implied by its name, always requires the presence of water. Herein, we report experimental evidence and mechanistic investigations that provide an alternative view to this process. We have demonstrated that water is not required to convert acetals and ketals to the corresponding carbonyls. The 1H NMR experimental results revealed that the TFA-mediated transformation of acetal to aldehyde occurs via a hemiacetal TFA ester intermediate, which differentiates itself from the classic acid-catalyzed hydrolysis, where the hemiacetal is the putative intermediate responsible for the formation of the aldehyde. More interestingly, alcohols are not the final byproducts as they are in the classical hydrolysis, rather, the two alcohol molecules are converted to two TFA esters under the reaction conditions. On the basis of theNMRevidence, we have proposed that the two TFA esters are formed in two separate steps via a different mechanism along the reaction pathway. Formation of the TFA esters renders the reaction irreversible. To the best of our knowledge, the cascade reaction pathway presented by the TFA-mediated conversion of acetals and ketals to carbonyls has never been previously postulated.
- Li, Wei,Li, Jianchang,Wu, Yuchuan,Fuller, Nathan,Markus, Michelle A.
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supporting information; experimental part
p. 1077 - 1086
(2010/04/04)
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- Synthesis, characterization and structure of DBU-hydrobromide-perbromide: A novel oxidizing agent for selective oxidation of alcohols to carbonyl compounds
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A new and efficient reagent for the conversion of primary and secondary alcohols into their corresponding aldehydes and ketones is introduced. The reagent was easily prepared from the reaction of DBU with molecular bromine in CHCl3. The structure of the reagent as DBUH+Br 3- was determined by single crystal X-ray diffraction analysis.
- Bakavoli, Mehdi,Rahimizadeh, Mohammad,Eshghi, Hossein,Shiri, Ali,Ebrahimpour, Zahra,Takjoo, Reza
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experimental part
p. 949 - 952
(2010/10/18)
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- Catalytic strategies for sustainable oxidations
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Several catalytic protocols for the oxidation of hydro-soluble substrates are presented that employ totally inorganic and robust polyoxometalate-based catalysts as well as porphyrin sensi-tizers, fullerenes and hybrid conjugates. Strategies for the imple-mentation of the system stability and efficiency are discussed.
- Carraro, Mauro,Sartorel, Andrea,Scorrano, Gianfranco,Carofiglio, Tommaso,Bonchio, Marcella
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experimental part
p. 1971 - 1978
(2009/04/07)
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- Selective partial hydrogenation of hydroxy aromatic derivatives with palladium nanoparticles supported on hydrophilic carbon
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Selective hydrogenation of phenol to cyclohexanol in the aqueous phase was achieved using a new catalytic system based on palladium particles supported on hydrophilic carbon prepared by one-pot hydrothermal carbonisation. The Royal Society of Chemistry.
- Makowski, Philippe,Demir Cakan, Rezan,Antonietti, Markus,Goettmann, Frederic,Titirici, Maria-Magdalena
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p. 999 - 1001
(2008/09/21)
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- m-iodosylbenzoic acid as a convenient recyclable reagent for highly efficient RuCl3-catalyzed oxidation of alcohols to carbonyl compounds
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m-Iodosylbenzoic acid selectively oxidizes primary and secondary alcohols to the respective carbonyl compounds in the presence of RuCl3 (0.5 mol%) at room temperature in aqueous acetonitrile. Separation of pure products is conveniently achieved by scavenging any aryl iodide by ion exchange with IRA-900 (hydroxide form) or by simple extraction of the basic aqueous solution with water. The reduced form of the reagent, m-iodobenzoic acid, can be easily recovered from the ion-exchange resin or from the basic aqueous solution by simple acidification with HCl. Georg Thieme Verlag Stuttgart.
- Yusubov, Mekhman S.,Gilmkhanova, Marina P.,Zhdankin, Viktor V.,Kirschning, Andreas
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p. 563 - 566
(2007/10/03)
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- Liquid phase oxidation of alkenes with nitrous oxide to carbonyl compounds
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A variety of substrates including linear, cyclic, heterocyclic alkenes and their derivatives were tested in the liquid phase non-catalytic oxidation with nitrous oxide (N2O). The structure and composition of the alkenes have a significant effect on the reaction selectivity. With many alkenes, N 2O oxidation provides a selective way for the preparation of carbonyl compounds. The generation of carbene (or diazomethane) species is a remarkable feature of the oxidation of terminal alkenes.
- Starokon,Dubkov,Babushkin,Parmon,Panov
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p. 268 - 274
(2007/10/03)
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- Hydrolysis of acetals in water under hydrothermal conditions
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A simple method for the hydrolysis of acetals and ketals was accomplished in neutral water or aqueous media by hydrothermal treatment without using acidic reagents. The deacetalization reaction was effectively accelerated in the presence of calcium chloride. Because no acidic catalysts were employed, neutralization of the reaction mixture was not necessary after the reaction. This sequence was successfully applied to the hydrolysis of chitosan, a biodegradable polyaminosaccharide.
- Sato, Kimihiko,Kishimoto, Tsutomu,Morimoto, Minoru,Saimoto, Hiroyuki,Shigemasa, Yoshihiro
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p. 8623 - 8625
(2007/10/03)
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- Mild and chemoselective catalytic deprotection of ketals and acetals using cerium(IV) ammonium nitrate
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Cerium(IV) ammonium nitrate (CAN) is a powerful, though mild, reagent for the efficient and selective removal of a range of ketals and acetals. This novel deprotection method requires only catalytic amounts of CAN and tolerates a variety of functional and protecting groups. Mechanistic insights suggest that the Ce(IV) salts act as unique Lewis acids and not as redox active species.
- Ates, Ali,Gautier, Arnaud,Leroy, Bernard,Plancher, Jean-Marc,Quesnel, Yannick,Vanherck, Jean-Christophe,Markó, István E.
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p. 8989 - 8999
(2007/10/03)
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- Microreactors for oxidations using fluorine
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Continuous flow gas-liquid thin film microreactors have been effectively used for the oxidation of alcohols and Baeyer-Villiger oxidation of ketones using elemental fluorine.
- Chambers, Richard D.,Holling, Darren,Rees, Anthony J.,Sandford, Graham
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- New applications of solid silica chloride (SiO2-Cl) in organic synthesis. Efficient preparation of diacetals of 2,2-bis(hydroxymethyl)-1,3-propanediol from different substrates and their transthioacetalization reactions. Efficient regeneration of carbonyl compounds from acetals and acylals
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A new application of solid silica chloride, an easily available and efficient catalyst for the preparation of diacetal of 2,2-bis-(hydroxymethyl)-1,3-propanediol from aldehydes, acetals, acylals, and oximes, is described. Transthioacetalization of diacetals of 2,2-bis-(hydroxymethyl)-1,3-propanediol into their corresponding 1,3-dithianes and 1,3-dithiolanes in the presence of silica chloride is presented. Efficient regeneration of carbonyl compounds from their corresponding acetals, ketals, diacetals, and acylals in the presence of this catalyst also is described.
- Firouzabadi, Habib,Iranpoor, Nasser,Hazarkhani, Hassan
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p. 2847 - 2858
(2007/10/03)
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- Reaction of cyclic ketals with ceric ammonium nitrate in acetonitrile/water
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The possibility of performing the hydrolysis of cyclic acetals and ketals under basic or mildly alkaline conditions by ceric ammonium nitrate (CAN) in MeCN/H2O or in 10% aq. methanol is rejected. However a role for Ce(IV) as Lewis acid is evidenced at pH 4.4. Under these conditions, which allow hydrolysis of cyclic ketals leaving glycosidic bonds unaltered, a selectivity of ketal cleavage due to steric hindrance is also observed. Similar yields are obtained when acetone/water replaces MeCN/H2O as solvent.
- Manzo, Emiliano,Barone, Gaspare,Bedini, Emiliano,Iadonisi, Alfonso,Mangoni, Lorenzo,Parrilli, Michelangelo
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p. 129 - 133
(2007/10/03)
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- Pd(II)-hydrotalcite-catalyzed oxidation of alcohols to aldehydes and ketones using atmospheric pressure of air
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A heterogenized Pd catalyst, Pd(II)-hydrotalcite (palladium(II) acetate-pyridine supported by hydrotalcite) catalyzes the aerobic oxidation in toluene of a variety of primary and secondary alcohols into the corresponding aldehydes and ketones in high yields using atmospheric pressure of air as a sole oxidant under mild conditions. This catalyst is also effective for the oxidation of allylic alcohols, especially such as geraniol and nerol, without any isomerization of an alkenic part. The catalyst can be easily prepared from all commercially available reagents and reused several times.
- Kakiuchi,Maeda,Nishimura,Uemura
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p. 6620 - 6625
(2007/10/03)
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- A comparison of the thermal decomposition of nitramines and difluoramines
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The decomposition rates and product distributions of a number of nitro- and difluoramino-substituted six-membered rings were compared: nitrocyclohexane (I); 1,1-dinitro-cyclohexane (II); 1,1,4,4-tetranitrocyclohexane (III), 1,1,4,4-tetrakis(difluoramino)cyclohexane (IV); 1,4-dinitropiperazine (V); 1,4,4-trinitropiperidine (VI), and 4,4-bis(difluoramino)-1-nitropiperidine (VII). The study suggested the following order for susceptibility to decomposition: N-NO2 > C-(NO2)2 > C-(NF2)2 The difference in bond energies among the compounds is small. Geminal bis(difluoramino) compounds appeared to be somewhat more stable than the corresponding gem-dinitro compounds though they released more heat during decomposition. Where a nitramine functionality was present, the nitroso analogue was observed as a major decomposition product. The decomposition of gem-bis(difluoramino) and gem-dinitro compounds exhibited similarities. Both experienced loss of one geminal NX2 group followed by the rearrangement of the remaining NX2. Where X was oxygen, loss of the initial nitro by homolysis was favored; rearrangement of the remaining nitro followed by homolysis of NO resulted in a C=O bond. Where X was fluorine, the initial difluoramino may have been lost as HNF2. The remaining difluoramino reacted by losing fluorine, leaving C=NF or by losing HNF, resulting in =C-F; the latter was mainly observed.
- Oxley,Smith,Zhang,Bedford
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p. 579 - 590
(2007/10/03)
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- Ruthenium-catalyzed oxidation of alkanes with tert-butyl hydroperoxide and peracetic acid
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The ruthenium-catalyzed oxidation of alkanes with tert-butyl hydroperoxide and peracetic acid gives the corresponding ketones and alcohols highly efficiently at room temperature. The former catalytic system, RuCl2(PPh3)3-t-BuOOH, is preferable to the oxidation of alkylated arenes to give aryl ketones. The latter system, Ru/C-CH3CO3H, is suitable especially for the synthesis of ketones and alcohols from alkanes. The ruthenium-catalyzed oxidation of cyclohexane with CH3CO3H in trifluoroacetic acid/CH2Cl2 at room temperature gave cyclohexyl trifluoroacetate and cyclohexanone with 90% conversion and 90% selectivity (85:15). The mechanistic study indicates that these catalytic oxidations of hydrocarbons involve oxo-ruthenium species as key intermediates.
- Murahashi,Komiya,Oda,Kuwabara,Naota
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p. 9186 - 9193
(2007/10/03)
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- Efficient oxidation of alcohols to carbonyl compounds with molecular oxygen catalyzed by N-hydroxyphthalimide combined with a Co species
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Highly efficient catalytic oxidation of alcohols with molecular oxygen by N-hydroxyphthalimide (NHPI) combined with a Co species was developed. The oxidation of 2-octanol in the presence of catalytic amounts of NHPI and Co(OAc)2 under atmospheric dioxygen in AcOEt at 70 °C gave 2-octanone in 93% yield. The oxidation was significantly enhanced by adding a small amount of benzoic acid to proceed smoothly even at room temperature. Primary alcohols were oxidized by NHPI in the absence of any metal catalyst to form the corresponding carboxylic acids in good yields. In the oxidation of terminal vic-diols such as 1,2-butanediol, carbon-carbon bond cleavage was induced to give one carbon less carboxylic acids such as propionic acid, while internal vic-diols were selectively oxidized to 1,2-diketones.
- Iwahama, Takahiro,Yoshino, Yasushi,Keitoku, Takashi,Sakaguchi, Satoshi,Ishii, Yasutaka
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p. 6502 - 6507
(2007/10/03)
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- Remarkably efficient deprotection of cyclic acetals and ketals
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A simple and mild procedure for the efficient deprotection of cyclic acetals and ketals, using cerium ammonium nitrate (CAN) is reported. The method tolerates a range of functional and protecting groups and is suitable for acid-labile substrates.
- Ates, Ali,Gautier, Arnaud,Leroy, Bernard,Plancher, Jean-Marc,Quesnel, Yannick,Marko, Istvan E.
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p. 1799 - 1802
(2007/10/03)
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- An efficient method for deprotection of acetals
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A variety of acetonides and acetals were efficiently cleaved using CuCl2.2H2O in MeCN. The method was effectively used in synthesis of chiral diols which are important in asymmetric synthesis.
- Saravanan,Chandrasekhar,Anand, R. Vijaya,Singh, Vinod K.
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p. 3091 - 3092
(2007/10/03)
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- Diozonides from coozonolyses of suitable O-methyl oximes and ketones
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Ozonolyses of the O-methyl oximes of cyclic ketones 5a - c in the presence of 1,4-cyclohexanedione (6) and ozonolyses of the O-methylated dioxime 8 of 1,4-cyclohexanedione in the presence of cycloketones 7a - c afforded the corresponding diozonides 11. Ozonolysis of the O-methyl oxime of acetone gave diozonide 18 in the presence of 6 and diozonide 21 in the presence of butanedione. Ozonolysis of the O-methyl oxime of cyclohexanone in the presence of butanedione gave diozonide 22. In addition, representatives of the hitherto unknown types of dispiro ozonides 12 having a lactam ring system have been obtained from the ozonolyses of 8 and 7.
- Griesbaum, Karl,Liu, Xuejun,Dong, Yuxiang
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p. 5463 - 5470
(2007/10/03)
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- Oxidation of Diols and Ethers by NaBrO3/NaHSO3 Reagent
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NaBrO3 combined with NaHSO3 was found to be an excellent oxidizing reagent of alcohols, diols, and ethers under mild conditions. A variety of aliphatic and cyclic diols were selectively oxidized with satisfactory yields to the corresponding hydroxy ketones and/or diketones, which are difficult to selectively prepare due to a concomitant formation of cleaved products. For example, 2-hydroxycyclohexanone and 1,2-cyclohexanedione were selectively formed by allowing 1,2-cyclohexanediol to react with NaBrO3/NaHSO3 reagent in a selected solvent. On the other hand, an alkyl ether, such as dioctyl ether, reacted with NaBrO3/NaHSO3, in water at room temperature to give octyl octanoate in 82% yield. The same oxidation at higher temperature (60°C) produced the α-brominated ester, octyl 2-bromooctanoate, which is considered to be formed through an alkenyl alkyl ether as the intermediate. The treatment of 1-ethoxy-l-heptene with NaBrO3/NaHSO3 afforded ethyl 2-bromoheptanoate and 2-bromoheptanoic acid as the major products.
- Sakaguchi, Satoshi,Kikuchi, Daisuke,Ishii, Yasutaka
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p. 2561 - 2566
(2007/10/03)
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- Elemental fluorine. Part 7. New oxidation methodology
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Reaction of fluorine with water in the presence of acids provides new oxidants for 'in-situ' oxidation of ketones. Direct reaction of fluorine with anhydrous alcohols and 1,2-diols provides simple methodology for oxidation to corresponding secondary ketones or α-hydroxy ketones.
- Chambers, Richard D.,Hutchinson, John,Sandford, Graham,Shah, Aneela,Vaughan, Julian F. S.
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p. 15833 - 15842
(2007/10/03)
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- Efficient desymmetrization of 1,2 and 1,3 diols by dimethyldioxirane
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Dimethyldioxirane was used to monooxide 1,2 and 1,3 sec,sec-diols to the corresponding ketoalcohols, exploiting the inhibiting effect of the formed carbonyl group on the course of the process.
- Bovicelli, Paolo
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p. 3031 - 3034
(2007/10/02)
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- Aerobic oxidation of alcohols to carbonyl compounds catalyzed by N-hydroxyphthalimide (NHPI) combined with Co(acac)3
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Aerobic oxidation of various alcohols has been accomplished by using a new catalytic system. N-hydroxyphthalimide (NHPI) combined with Co(acac)3. The oxidation of alcohols by NHPI was found to be markedly enhanced by adding a slight amount of Co(acac)3 (0.05 equiv. to NHPI). Thus, secondary alcohols and vic-diols which are difficult to be oxidized by NHPI alone were smoothly oxidized with molecular oxygen (1 atm) to the corresponding carbonyl compounds under relatively mild conditions (65 ~ 75 °C).
- Iwahama, Takahiro,Sakaguchi, Satoshi,Nishiyama, Yutaka,Ishii, Yasutaka
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p. 6923 - 6926
(2007/10/02)
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- Aluminium trichloride hexahydrate-zinc-THF-A new system for the reduction of carbon-carbon double bonds
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Aluminium trichloride hexahydrate-Zn-THF system selectivity reduces α,β-unsatureted carbonyl and enedicarbonyl compounds to the corresponding dihydro compounds in good yields.
- Konwar, Dilip,Dutta, Dilip Kumar,Sandhu, Jagir Singh
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p. 725 - 727
(2007/10/03)
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- Enzymatic Preparation of Chiral 4-Hydroxy-2,2-dimethyl-1-cyclohexanone as a Chiral Building Block
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(S)-4-Hydroxy-2,2-dimethyl-1-cyclohexanone (1a) was prepared by two enzymatic methods. 1,4-Cyclohexanediol was converted to monoacetal (11) via (+/-)-1a.Enzymatic reduction of 11 by baker's yeast gave (S)-1 of almost 100 percent e.e.Direct hydroxylation of 2,2-dimethyl-1-cyclohexanone (14) by P-450 camphor monooxygenase of the cloned genes of Pseudomonas putida PpG1 gave (S)-1a of almost 100 percent e.e., too.According to Mitsunobu's method, SN-2 inversion of (S)-1 gave (R)-1.
- Yamamoto, Hiroshi,Oritani, Takayuki,Koga, Hideo,Horiuchi, Tadao,Yamashita, Kyohei
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p. 1915 - 1921
(2007/10/02)
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- Barium Permanganate, Ba(MnO4)2, a versatile and mild oxidizing agent for use under aprotic and non-aqueous conditions
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Barium Permanganate is an easily prepared, stable, and a versatile oxidation reagent. With this reagent different types of primary and secondary hydroxy compounds are converted to their carbonyl derivatives. Aldehydes could be transformed to their carboxylic acids. Benzylic chloride and bromides are converted to their aldehydes and carboxylic acids. Semicarbazide and 2,4-dinitrophenylhydrazine derivatives of benzylic carbonyl compounds undergo carbon-nitrogen bond cleavage selectively and yield the expected carbonyl compounds. p-Hydroquinone is converted to p-benzoguinone and aromatic amines to their azo compounds. Anthracene and phenanthrene produce their 9,10-quinones. Diphenyl acetylene and trans stilbene give benzil, and styrene produces benzaldehyde. Selective oxidations of secondary benzylic carbon-hydrogen bonds occur and the corres- ponding carbonyl compounds are produced in good yields.
- Firouzabadi,Seddighi,Mottaghineiad,Bolourchian
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p. 6869 - 6878
(2007/10/02)
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- REMOTE OXIDATION OF KETONES TO γ- AND δ-DIKETONES
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A single stage remote oxidation of ketones to γ- and δ-diketones has been carried out in a sodium peroxysulfate-iron(II) sulfate system.
- Troyanskii, E.I.,Mizintsev, V. V.,Lazareva, M. I.,Demchuk, D. V.,Nikishin, G. I.
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p. 1879 - 1884
(2007/10/02)
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- Simple and Chemoselective Deprotection of Acetals Using Aqueous Dimethyl Sulfoxide
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Deprotection of acetals was achieved in aqueous dimethyl sulfoxide under neutral reaction condition.Selective cleavage of acyclic acetals bearing various types of acid labile protecting groups was also reported.
- Kametani, Tetsuji,Kondoh, Hirotsune,Honda, Toshio,Ishizone, Hiroyuki,Suzuki, Yukio,Mori, Wakako
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p. 901 - 904
(2007/10/02)
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- Ring-Expansion Reactions Catalyzed by Hydrophobic Vitamin B12 in Synthetic Bilayer Membrane
-
Heptapropyl cobyrinate perchlorate catalyzed the ring-expansion reactions, which convert 2-methyl-1,3-cyclopentanedion and 3-methyl-2-pyrrolidinone into 1,4-cyclohexanedione and 2-piperidinone, respectively, in single-compartment bilayer vesicles.
- Murakami, Yukito,Hisaeda, Yoshio,Ohno, Teruhisa,Matsuda, Yoshihisa
-
p. 621 - 624
(2007/10/02)
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- Hydrogenation of Benzene Ring by Paired Electrosynthesis with Raney-Nickel Cathode
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Paired electrolysis with 1,4-dimethoxybenzene (1) as a substrate was studied.Hydrogenation of the aromatic ring occurred to produce 1,4-cyclohexanedione (4) and two derivatives on Raney-nickel cathode.Two derivatives were converted into 4 by treatment of HCl aqueous solution.The total yield of 4 was 60percent based on 1, whereas 4 was not formed on a platinium or lead cathode.
- Yamada, Tsukasa,Osa, Tetsuo,Matsue, Tomokazu
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p. 1989 - 1992
(2007/10/02)
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