- Hydrogenation of coumarin to octahydrocoumarin over a Ru/C catalyst
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The production of octahydrocoumarin, which can serve as a replacement for toxic coumarin, was investigated using 5% Ru on active carbon (Ru/C) as the catalyst for the hydrogenation of coumarin. The hydrogenation was studied by optimizing the reaction conditions (pressure, solvent and coumarin concentration). The activity and selectivity of the Ru/C catalyst were compared for different solvents. The mechanism of coumarin hydrogenation was deduced. The formation of side products was explained. The optimal hydrogenation reaction conditions were: 130 °C, 10 MPa, 60 wt% coumarin in methanol, and 0.5 wt% (based on coumarin) of Ru/C catalyst. At the complete conversion of coumarin, the selectivity to the desired product was 90%.
- Bílková, Dana,Jansa, Petr,Paterová, Iva,?erveny, Libor
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- Cerium-Catalyzed Hydrosilylation of Acrylates to Give α-Silyl Esters
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The homoleptic organocerium complex Ce{C(SiHMe2)3}3(1) reacts with B(C6F5)3to produce the zwitterionic bis(alkyl) hydridoborato Ce{C(SiHMe2)3}2HB(C6F5)3(2). NMR and IR spectroscopy and X-ray crystallography indicate that each alkyl ligand contains two bridging Ce?H-Si interactions in both 1 and 2. Compound 2 serves as a precatalyst for the hydrosilylation of acrylates to give α-silyl esters at room temperature with a turnover number of 2200.
- Pindwal, Aradhana,Patnaik, Smita,Everett, William C.,Ellern, Arkady,Windus, Theresa L.,Sadow, Aaron D.
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- Bi(OTf)3-catalyzed Baeyer-Villiger oxidation of carbonyl compounds with m-CPBA
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An efficient method has been developed for the Baeyer-Villiger oxidation of a variety of carbonyl compounds with m-CPBA to afford the corresponding esters/lactones using bismuth triflate as catalyst. The catalyst is reused for Baeyer-Villiger oxidation without significant loss of catalytic activity for three cycles.
- Alam, M. Mujahid,Varala, Ravi,Adapa, Srinivas R.
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- Synthesis of 6-, 7-, and 8-membered lactones via the nickel-catalysed electrochemical arylation of electron-deficient olefins
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A nickel-catalysed electroreductive process of arylation of α,β-unsaturated carboxylic esters has been applied to the synthesis of medium-sized lactones. Of the two possible approaches investigated in this study, the most efficient one involves first the electrochemical condensation, followed by the lactonisation.
- De Mendon?a Cavalcanti, Janesmar Camilo,Fonseca Goulart, Marilia Oliveira,Léonel, Eric,Nédélec, Jean-Yves
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- An efficient synthesis of dihydrocoumarins
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Dihydrocoumarins are obtained in 40 to 60% yields in one step by heating acrylic esters with an excess of a phenol in the presence of base catalysts.
- Pickett, James E.,Van Dort, Paul C.
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- Palladium nanoparticles stabilised by PTA derivatives in glycerol: Synthesis and catalysis in a green wet phase
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Palladium nanoparticles stabilised by N-substituted 1,3,5-triaza-7-phosphaadamantane ionic ligands were synthesised from Pd(II) precursors and characterised in neat glycerol, observing an important effect of the phosphine nature in the dispersion of the nanoclusters in solution. The most homogeneously dispersed nanoparticles (Pd1a) led to the best catalytic behaviour in the benchmark Suzuki-Miyaura reaction. From this screening, Pd1a was applied in different CC cross-couplings and hydrogenation reactions, isolating the expected products in high yields (> 90%). An efficient catalyst immobilisation in glycerol was attained (up to ten runs without any sign of activity loss).
- Chahdoura, Faouzi,Favier, Isabelle,Pradel, Christian,Mallet-Ladeira, Sonia,Gómez, Montserrat
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- HYDROGENATION OF OXYGEN-CONTAINING HETEROCYCLIC COMPOUNDS ON GROUP VIII METALS
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The hydrogenation of a number of oxygen-containing heterocyclic compounds on Pt, Pd, and Rh blacks in the liquid phase at atmospheric pressure was investigated.The results are compared with data on H-D exchange with D2O and are interpreted from the point of view of the theory of ?-complex adsorption.
- Karakhanov, E. A.,Dedov, A. G.,Loktev, A. S.
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- Heterogeneous Baeyer-Villiger oxidation of ketones using m- chloroperbenzoic acid catalyzed by hydrotalcites
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Hydrotalcites promote the Baeyer-Villiger oxidation of various ketones using m-chloroperbenzoic acid to give high yields of lactones and esters.
- Kaneda, Kiyotomi,Yamashita, Toyokazu
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- SmI2 mediated Barbier reaction of α-fluoro ethers
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Addition of α-fluoro ethers to cyclohexanone in THF at ambient temperature has been mediated by means of SmI2.
- Ringom, Rune,Benneche, Tore
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- Selective Hydrogenation of Unsaturated Carbon-Carbon Bonds in Aromatic-Containing Platform Molecules
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The combination of chemical and biological catalysis enables the production from biomass of coumarin and dihydrocoumarin (DHC), opening new routes to the formation of fine chemicals and pharmaceutical building blocks. Each of these products requires the hydrogenation of 4-hydroxycoumarin (4HC) to 4-hydroxydihydrocoumarin (4HDHC), which, in turn, requires the reduction of an unsaturated C-C bond in the presence of an aromatic ring. Using in situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, we show that reaction at 348 K over monometallic Pd catalysts leads to the partial reduction of the aromatic ring in 4HC, obtaining 93% selectivity for C=C bond hydrogenation at 82% 4HC conversion and with a low turnover frequency (TOF). Decreasing the Pd dispersion from 70% to 6% not only leads to an increase in the rate of 4HC hydrogenation, but it also leads to an increase in the rate of overhydrogenation. However, the formation of bimetallic PdAu nanoparticles inhibits the overhydrogenation reaction while also doubling the TOF to a value of 6 ks-1 for 4HDHC production. A bimetallic PdAu catalyst supported on SiO2 leads to 97% selectivity for C=C bond hydrogenation at 86% 4HC conversion, while an acidic support such as amorphous silica-alumina can be used to produce DHC directly from 4HC.
- Schwartz, Thomas J.,Lyman, Spencer D.,Motagamwala, Ali Hussain,Mellmer, Max A.,Dumesic, James A.
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- Tetrahedral Intermediate in Acyl Transfer Reactions. A Revaluation of the Significance of Rate Data Used in Deriving Fundamental Linear Free Energy Relationships
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A theoretical investigation of model mechanisms applicable to acyl transfer reactions in solution has shown that the interpretations of experimental rate constants in terms of mechanistic constants are all subject to an ambiguity that is well-known in principle but usually ignored or incorrectly evaluated in practice.For all models involving reversibly formed tetrahedral intermediates, the experimental constants are products of the form kffp in which kf is equal to ki+>n or to ki and fp is a product distribution fraction.Each assesible pH range can give a maximum of one constant that depends on the pH; there is no way to dissect out the desired mechanistic constants or the equilibrium constants for several tetrahedral intermediates unless some independent means can be developed to measure the fp.These conclusions are of major concern to all studies that attempt to relate reactivity to structure.Representative acyl transfer reactions have been reinterpreted.One example of the so-called trialkyl lock acceleration is now shown to amount to a factor of about 4000 for the mechanistic rates in contrast to the factor of 5*1010 originally proposed.Most of the decrease in estimate arises from recent reevaluations on observed rates, but there is a further decrease by a factor of 100 in the mechanistic rates due to considerations treated in present study.Evidence is also presented that certain acyl transfer reactions in solution may proceed by direct displacement rather than though a reversibly formed tetrahedral intermediate.
- DeTar, DeLos F.
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- Recyclable selective palladium-catalyzed synthesis of five-, six- or seven-membered ring lactones and lactams by cyclocarbonylation in ionic liquids
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The ionic liquids, BMIM PF6 or BMIM NTf2, are used successfully for the palladium-catalyzed cyclocarbonylation of 2-allylphenols and anilines, 2-vinylphenols, and 2-aminostyrenes. The reaction proceeds cleanly and efficiently to afford high yields of lactones or lactams with good or excellent selectivity for one isomer. The ionic liquid containing the palladium catalyst, and ligand, is recyclable in all cases.
- Ye, Fangguo,Alper, Howard
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- Industrial production method of 4-hydroxy-1-indanone
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The invention discloses an industrial production method of 4-hydroxy-1-indanone, and relates to the technical field of organic chemistry, the industrial production method comprises the following steps: taking dihydrocoumarin as a raw material, carrying out hydrolysis reaction on the dihydrocoumarin under the catalysis of hydrochloric acid to obtain an intermediate 1, and carrying out cyclization reaction on the intermediate 1 and polyphosphoric acid under the catalysis of strongly acidic resin to obtain the 4-hydroxy-1-indanone. The preparation method disclosed by the invention is short in route, easily available in raw materials, high in yield, moderate in reaction condition, suitable for industrial production, less in three wastes, more environment-friendly, easier to operate and stable in process.
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- Reduction of Electron-Deficient Alkenes Enabled by a Photoinduced Hydrogen Atom Transfer
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Direct hydrogen atom transfer from a photoredox-generated Hantzsch ester radical cation to electron-deficient alkenes has enabled the development of an efficient formal hydrogenation under mild, operationally simple conditions. The HAT-driven mechanism is supported by experimental and computational studies. The reaction is applied to a variety of cinnamate derivatives and related structures, irrespective of the presence of electron-donating or electron-withdrawing substituents in the aromatic ring and with good functional group compatibility. (Figure presented.).
- Larionova, Natalia A.,Ondozabal, Jun Miyatake,Cambeiro, Xacobe C.
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supporting information
p. 558 - 564
(2020/12/07)
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- Cobalt-Catalyzed Aerobic Oxidative Cleavage of Alkyl Aldehydes: Synthesis of Ketones, Esters, Amides, and α-Ketoamides
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A widely applicable approach was developed to synthesize ketones, esters, amides via the oxidative C?C bond cleavage of readily available alkyl aldehydes. Green and abundant molecular oxygen (O2) was used as the oxidant, and base metals (cobalt and copper) were used as the catalysts. This strategy can be extended to the one-pot synthesis of ketones from primary alcohols and α-ketoamides from aldehydes.
- Li, Tingting,Hammond, Gerald B.,Xu, Bo
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supporting information
p. 9737 - 9741
(2021/05/31)
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- Hydrogenation reaction method
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The invention relates to a hydrogenation reaction method, and belongs to the technical field of organic synthesis. The hydrogenation reaction method provided by the invention comprises the following steps: carrying out a hydrogen transfer reaction on a hydrogen acceptor compound, pinacol borane and a catalyst in a solvent in the presence of proton hydrogen, so that the hydrogen acceptor compound is subjected to a hydrogenation reaction; the catalyst is one or more than two of a palladium catalyst, an iridium catalyst and a rhodium catalyst; the hydrogen acceptor compound comprises one or morethan two functional groups of carbon-carbon double bonds, carbon-carbon triple bonds, carbon-oxygen double bonds, carbon-nitrogen double bonds, nitrogen-nitrogen double bonds, nitryl, carbon-nitrogentriple bonds and epoxy. The method is mild in reaction condition, easy to operate, high in yield, short in reaction time, wide in substrate application range, suitable for carbon-carbon double bonds,carbon-carbon triple bonds, carbon-oxygen double bonds, carbon-nitrogen double bonds, nitrogen-nitrogen double bonds, nitryl, carbon-nitrogen triple bonds and epoxy functional groups, good in selectivity and high in reaction specificity.
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Paragraph 0034; 0209-0212
(2020/05/14)
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- Generalized Chemoselective Transfer Hydrogenation/Hydrodeuteration
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A generalized, simple and efficient transfer hydrogenation of unsaturated bonds has been developed using HBPin and various proton reagents as hydrogen sources. The substrates, including alkenes, alkynes, aromatic heterocycles, aldehydes, ketones, imines, azo, nitro, epoxy and nitrile compounds, are all applied to this catalytic system. Various groups, which cannot survive under the Pd/C/H2 combination, are tolerated. The activity of the reactants was studied and the trends are as follows: styrene'diphenylmethanimine'benzaldehyde'azobenzene'nitrobenzene'quinoline'acetophenone'benzonitrile. Substrates bearing two or more different unsaturated bonds were also investigated and transfer hydrogenation occurred with excellent chemoselectivity. Nano-palladium catalyst in situ generated from Pd(OAc)2 and HBPin extremely improved the TH efficiency. Furthermore, chemoselective anti-Markovnikov hydrodeuteration of terminal aromatic olefins was achieved using D2O and HBPin via in situ HD generation and discrimination. (Figure presented.).
- Wang, Yong,Cao, Xinyi,Zhao, Leyao,Pi, Chao,Ji, Jingfei,Cui, Xiuling,Wu, Yangjie
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supporting information
p. 4119 - 4129
(2020/08/10)
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- Diboron-Mediated Rhodium-Catalysed Transfer Hydrogenation of Alkenes and Carbonyls
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A diboron-mediated rhodium-catalysed transfer hydrogenation system using water as the hydrogen donor is developed. In addition to a series of alkenes with good functional group tolerance, this rhodium-based catalytic system also effectively reduces aldehydes and ketones. A plausible mechanism involving the RhI-catalysed hydrogen generation and Rh0-catalysed hydrogenation is proposed for the reaction.
- Lin, Xiao,Wang, Yuhan,Hu, Yan,Zhu, Wanjiang,Dou, Xiaowei
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supporting information
p. 1046 - 1049
(2020/02/25)
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- Nucleophilic aromatic substitution of unactivated fluoroarenes enabled by organic photoredox catalysis
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Nucleophilic aromatic substitution (SNAr) is a classical reaction with well-known reactivity toward electron-poor fluoroarenes. However, electron-neutral and electron-rich fluoro(hetero)arenes are considerably underrepresented. Herein, we present a method for the nucleophilic defluorination of unactivated fluoroarenes enabled by cation radical-accelerated nucleophilic aromatic substitution. The use of organic photoredox catalysis renders this method operationally simple under mild conditions and is amenable to various nucleophile classes, including azoles, amines, and carboxylic acids. Select fluorinated heterocycles can be functionalized using this method. In addition, the late-stage functionalization of pharmaceuticals is also presented. Computational studies demonstrate that the site selectivity of the reaction is dictated by arene electronics.
- Nicewicz, David A.,Pistritto, Vincent A.,Schutzbach-Horton, Megan E.
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supporting information
p. 17187 - 17194
(2020/11/02)
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- Ruthenium-Promoted Acceptorless and Oxidant-Free Lactone Synthesis in Aqueous Medium
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Ruthenium-catalyzed formation of lactones from diols in aqueous medium has been demonstrated. 1,3,5-Triazaphosphaadamantane (PTA) included water-soluble ruthenium complexes [RuCl 2 (PPh 3)(2,6-Py-(CH 2 -PTA) 2 ]·2Br and [RuCl 2 (PPh 3) 2 (2-PyCH 2 PTA)]·Br in the presence of KOH were found to be efficient for the synthesis of lactones from diols. The reported synthetic protocol is green as it uses water as solvent, avoids the use of any hydrogen acceptor/oxidant, and produces hydrogen as the only side product. Mechanistic studies revealed that lactone formation involved aldehyde intermediate and followed dehydrogenative pathway.
- Bhatia, Anita,Kannan, Muthukumar,Muthaiah, Senthilkumar
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supporting information
p. 721 - 725
(2019/03/26)
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- Formation of Enol Ethers by Radical Decarboxylation of α-Alkoxy β-Phenylthio Acids
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Enol ethers are formed by radical decarboxylation of α-alkoxy β-phenylthio acids via the corresponding Barton esters. The phenylthio acids were usually made by the known regioselective reaction of α,β-epoxy acids with PhSH in the presence of InCl3, followed by O-alkylation of the resulting alcohol. In one case, thiol addition to an α,β-unsaturated ethoxymethyl ester was used.
- Palanivel, Ashokkumar,Mubeen, Sidra,Warner, Thomas,Ahmed, Nayeem,Clive, Derrick L. J.
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p. 12542 - 12552
(2019/10/19)
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- Celite-Polyaniline supported palladium catalyst for chemoselective hydrogenation reactions
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Polyaniline coated on particles of celite is used as support to load palladium catalyst. This heterogenized Celite?PANI?Pd system, is used as an efficient catalyst for chemoselective hydrogenation reactions. The catalyst is characterized by usual spectral, analytical techniques and studied for hydrogenation reactions at ambient conditions. The mild reaction conditions allow the control over the reactions and excellent selectivity is achieved in number of conversions. Hydrogenation of a carbon–carbon double bond was favored over other polar π-bond systems, while labile functional groups such as benzyl ether, benzyl esters, cyano, nitro and halogen remained unaffected. Primary amines were converted to N,N-dimethyl amines with formaldehyde, the double bond of coumarin was selectively hydrogenated without opening of the lactone functionality.
- Patel, Heta A.,Rawat, Maitreyee,Patel, Arun L.,Bedekar, Ashutosh V.
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- Selective hydrogenation of α,β-unsaturated carbonyl compounds on silica-supported copper nanoparticles
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Silica-supported copper nanoparticles prepared via surface organometallic chemistry are highly efficient for the selective hydrogenation of various α,β-unsaturated carbonyl compounds yielding the corresponding saturated esters, ketones, and aldehydes in the absence of additives. High conversions and selectivities (>99%) are obtained for most substrates upon hydrogenation at 100-150 °C and under 25 bar of H2.
- Mendes-Burak, Jorge,Ghaffari, Behnaz,Copéret, Christophe
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supporting information
p. 179 - 181
(2019/01/04)
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- 1,1,2,2-Tetrahydroperoxy-1,2-Diphenylethane: An efficient and high oxygen content oxidant in various oxidative reactions
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Several oxidative approaches namely thiocyanation of aromatic compounds, epoxidation of alkenes, amidation of aromatic aldehydes, epoxidation of α β-unsaturated ketones, oxidation of sulfides to sulfoxides and sulfones, bayer-villeger reaction, bromination and iodation of aniline and phenol derivatives oxidative esterification, oxidation of pyridines and oxidation of secondary, allylic and benzyllic alcohols were carried out using 1,1,2,2-Tetrahydroperoxy-1,2-Diphenylethane as the potential solid oxidant which can be stored for several months without any loss in its activity. All of the procedures were accomplished via mild reaction conditions and the products were afforded in high yields and short reaction times.
- Khosravi, Kaveh,Naserifar, Shirin
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supporting information
p. 6584 - 6592
(2018/10/05)
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- Metal-Free Catalytic Reduction of α,β-Unsaturated Esters by 1,3,2-Diazaphospholene and Subsequent C-C Coupling with Nitriles
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1,3,2-Diazaphospholene 1 catalyzes the conjugate transfer hydrogenation as well as the 1,4-hydroboration of α,β-unsaturated esters. The initial step for both processes involves a 1,4-hydrophosphination of the α,β-unsaturated esters to afford a phosphinyl enol ether. Subsequent cleavage of the P-O bond in the phosphinyl enol ether by ammonia-borane (AB) generates an enol intermediate which tautomerizes to saturated esters, while the P-O bond cleavage by HBpin via a formal σ-bond metathesis affords boryl enolate intermediate. The latter could undergo a further coupling reaction with nitriles to form substituted amino diesters or 1,3-imino esters, depending on α,β-unsaturated ester substrates. These catalytic reactions can also be performed in a one-pot manner, illustrating a protocol for metal-free catalytic C-C bond construction.
- Chong, Che Chang,Rao, Bin,Kinjo, Rei
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p. 5814 - 5819
(2017/09/15)
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- One for Many: A Universal Reagent for Acylation Processes
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This work describes acylation reactions facilitated by a type of heterocycle-based acyl transfer agent, 2-acyloxypyridazinone. Reactions of 2-acyloxypyridazinone with carboxylic acids yield mixed carbonic anhydride intermediates, which are reactive and could be coupled with a wide range of substrates including acids, amines, alcohols, and thiols. The wide substrate scope, ease of operation (no additive or catalyst), storage and handling stability, and atom-efficiency from recycling the heterocycle carrier make the reported acylating agent attractive for acylation-based coupling reactions.
- Moon, Hyun Kyung,Sung, Gi Hyeon,Kim, Bo Ram,Park, Jong Keun,Yoon, Yong-Jin,Yoon, Hyo Jae
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supporting information
p. 1725 - 1730
(2016/06/09)
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- Hydrogenation of alkenes over nickel nanoparticles under atmospheric pressure of hydrogen
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Nickel nanoparticles have been shown to be an accessible catalyst which allows hydrogenation of unsaturated compounds to be accomplished under atmospheric pressure of hydrogen at relatively low temperatures. Linear and cyclic alkenes, styrene and norbornene derivatives, as well as pinenes and camphene have been smoothly hydrogenated under these conditions. In some cases, selective hydrogenation of unsaturated carbon–carbon bond is possible with the other functional group remaining intact.
- Mokhov,Popov, Yu. V.,Nebykov
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p. 319 - 323
(2016/06/06)
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- Palladium nanoparticles stabilised by cinchona-based alkaloids in glycerol: Efficient catalysts for surface assisted processes
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Palladium nanoparticles (PdNPs) were synthesised and fully characterised, both in solution and the solid state, using naturally-occurring cinchona-based alkaloids in neat glycerol. These nano-systems were stable under reaction conditions, finding applications in hydrogenation and hydrodehalogenation processes, as a result of their surface-like behaviour. Their reactivity was improved in relation to that involving PdNPs stabilised by phosphines and also by Pd/C as a heterogenous catalyst, mainly in terms of recyclability. In particular, the colloidal palladium catalyst stabilised by quinidine was highly efficient to promote the hydrodechlorination of aromatic compounds under low dihydrogen pressure. These original catalysts found applications in the synthesis of secondary and tertiary amines including N-substituted anilines, by means of one-pot tandem Pd-catalysed methodologies under smooth conditions. In all of these processes, glycerol performed a crucial function as a liquid support for the immobilisation of nanoparticle-based catalysts, allowing both the stabilisation of the nano-catalysts and easy recycling of the catalytic phase.
- Reina,Pradel,Martin,Teuma,Gómez
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p. 93205 - 93216
(2016/10/11)
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- Enzymatic synthesis of optically active lactones via asymmetric bioreduction using ene-reductases from the old yellow enzyme family
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In contrast to the widely studied asymmetric bioreduction of α,β-unsaturated carboxylic acid esters catalyzed by ene-reductases, the reaction applied to lactones remains unexplored. A broad set of ene-reductases was found to reduce various α-, β- and γ-substituted α,β-unsaturated butyrolactones to yield the corresponding saturated non-racemic lactones. Substitution patterns greatly influenced activities and stereoselectivities and lactone products were obtained in moderate to excellent yields; importantly, enzyme-based stereocontrol allowed access to both enantiomers in up to >99% ee. Chiral recognition of a distant γ-center led to kinetic resolution with remarkable enantioselectivities (E values up to 49). An unprecedented case of dynamic kinetic resolution was observed with 3-methyl-5-phenylfuran-2(5H)-one, whereby spontaneous racemization of the substrate furnished the product in up to 73% conversion and >99% ee and 96% de.
- Turrini, Nikolaus G.,Hall, Mélanie,Faber, Kurt
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supporting information
p. 1861 - 1871
(2015/06/02)
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- Imidazole derivatives as accelerators for ruthenium-catalyzed hydroesterification and hydrocarbamoylation of alkenes: Extensive ligand screening and mechanistic study
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Imidazole derivatives are effective ligands for promoting the [Ru3(CO)12]-catalyzed hydroesterification of alkenes using formates. Extensive ligand screening was performed to identify 2-hydroxymethylated imidazole as the optimal ligand. Neither carbon monoxide gas nor a directing group was required, and the reaction also showed a wide substrate generality. The Ru-imidazole catalyst system also promoted intramolecular hydrocarbamoylation to afford lactams. A Ru-imidazole complex was unambiguously analyzed by X-ray crystallography, and it had a trinuclear structure derived from one [Ru3(CO)12] and two ligands. This complex was also successfully used for hydroesterification. The mechanism was examined in detail by using D- and 13C-labeled formates, indicating that the hydroesterification reaction proceeds by a decarbonylation-recarbonylation pathway. Effective imidazole assistant: [Ru3(CO)12]-catalyzed hydroesterification of alkenes by using formates is drastically accelerated by imidazole derivatives and exhibits a broad substrate scope for both alkenes and formates. The Ru-imidazole complex also catalyzes the intramolecular hydrocarbamoylation of alkenes.
- Konishi, Hideyuki,Muto, Takashi,Ueda, Tsuyoshi,Yamada, Yayoi,Yamaguchi, Miyuki,Manabe, Kei
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p. 836 - 845
(2015/03/14)
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- A cooperative N-heterocyclic carbene/palladium catalysis system
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N-heterocyclic carbenes (NHC) have been extensively studied as organocatalysts and ligands for transition metals, but the successful integration of NHCs and late transition metals in cooperative catalysis remains an underexplored area. We have developed a cooperative palladium-catalyzed allylation of NHC-activated aldehydes to access a variety of 3-allyl dihydrocoumarin derivatives. Kinetic experiments support a cooperative pathway for this transformation.
- Liu, Kun,Hovey, M. Todd,Scheidt, Karl A.
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p. 4026 - 4031
(2014/10/15)
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- Palladium nanoparticles in glycerol: A versatile catalytic system for C-X bond formation and hydrogenation processes
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Palladium nanoparticles stabilised by tris(3-sulfophenyl)phosphine trisodium salt in neat glycerol have been synthesised and fully characterised, starting from both Pd(II) and Pd(0) species. The versatility of this innovative catalytic colloidal solution has been proved by its efficient application in C-X bond formation processes (X=C, N, P, S) and C-C multiple bond hydrogenation reactions. The catalytic glycerol phase could be recycled more than ten times, preserving its activity and selectivity. The scope of each of these processes has demonstrated the power of the as-prepared catalyst, isolating the corresponding expected products in yields higher than 90%. The dual catalytic behaviour of this glycerol phase, associated to the metallic nanocatalysts used in wet medium (molecular- and surface-like behaviour), has allowed attractive applications in one-pot multi-step transformations catalysed by palladium, such as C-C coupling followed by hydrogenation, without isolation of intermediates using only one catalytic precursor. Copyright
- Chahdoura, Faouzi,Pradel, Christian,Gomez, Montserrat
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supporting information
p. 3648 - 3660
(2014/01/06)
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- Remarkable improvement achieved by imidazole derivatives in ruthenium-catalyzed hydroesterification of alkenes using formates
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Imidazole derivatives are revealed to be effective ligands in the Ru-catalyzed hydroesterification of alkenes using formates, affording one-carbonelongated esters in high yields. Further, intramolecular hydroesterification was successfully performed to give lactones for the first time. Imidazole derivatives can contribute to promote the reaction as well as to suppress the undesired decarbonylation of formate. Toxic CO gas, a directing group, and large excess alkenes are not required.
- Konishi, Hideyuki,Muto, Takashi,Manabe, Kei,Ueda, Tsuyoshi
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supporting information
p. 4722 - 4725,4
(2012/12/12)
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- TMSOTf-catalyzed intramolecular seleno-arylation of tethered alkenes: A novel method for the solid-phase synthesis of dihydrocoumarins and coumarins
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TMSOTf-catalyzed intramolecular seleno-arylation of tethered alkenes was performed using polystyrene-supported succinimidyl selenide as the selenium source. This catalytic process provides an efficient method for the regioselective synthesis of dihydrocoumarins possessing a seleno-functionality, followed by traceless cleavage of selenium linker to provide dihydrocoumarins and coumarins in good yields and purities.
- Tang,Li, Wen,Gao, Zhang Yong,Gu, Xi
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experimental part
p. 631 - 634
(2012/07/03)
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- Homogeneous hydrogenation of electron-deficient alkenes by iridium complexes
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The catalytic homogeneous hydrogenation of electron-deficient alkenes (nucleophilic hydrogenation) was achieved in the presence of iridium complexes and a base as co-catalyst. Contrary to hydrogenation of electron-rich alkenes, which is inactivated by bases, the hydrogenation of the electron-deficient alkenes turned out to be base activated. Here, we present a more thorough study on the capacities but also limitations of this new reaction mechanism using screenings of the reaction conditions as well as different Ir complexes and substrates. The formation of a catalytically active Ir complex is proposed. The active complex usually attacks a soft electron-deficient atom, if more than one possibility exists (as shown by density functional theory computations). Additionally, first examples of enantiomeric enrichments in the presence of chiral Ir complexes are presented. The high catalyst load needed and the moderate yields show that the active complex is very unstable under conditions of nucleophilic hydrogenation and is quickly deactivated, which has to be addressed in further studies. Copyright
- Semeniuchenko, Volodymyr,Exner, Thomas E.,Khilya, Volodymyr,Groth, Ulrich
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experimental part
p. 804 - 809
(2012/03/26)
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- Radical reductions of alkyl halides bearing electron withdrawing groups with N-heterocyclic carbene boranes
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1,3-Dimethylimidazol-2-ylidene borane and 2,4-dimethyl-1,2,4-triazol-3- ylidene borane are found to be useful reagents for the reduction of alkyl iodides and bromides bearing nearby electron withdrawing substituents. Signatures of radical chain reactions are seen in many cases, but ionic reductions may also be occurring with some substrates. The reagents are attractive because of their low molecular weight, their availability from inexpensive precursors, and their stability. Separation of the borane products from the target products is readily accomplished either with or without prior regeneration of the borane for later reuse. 2,4-Dimethyl-1,2,4-triazol-3-ylidene borane is versatile because both starting borane and its derived products can be removed by extraction with water.
- Ueng, Shau-Hua,Fensterbank, Louis,Lacote, Emmanuel,Malacria, Max,Curran, Dennis P.
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supporting information; experimental part
p. 3415 - 3420
(2011/06/25)
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- The Baeyer-Villiger oxidation of ketones with Oxone in the presence of ionic liquids as solvents
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Cyclic and linear ketones were readily oxidised with Oxone at 40 °C in ionic liquids as solvents and short times (2.5-20 h), affording their corresponding lactones and esters in high yields (65-95%). Both, aprotic and protic ionic liquids were used. The best conversion of ketones and the highest yields of products were obtained with 1-buty-3-methylimidazolium tetrafluoroborate and 1-methylimidazolium acetate as solvents. These ionic liquids were also efficiently recycled in the Baeyer-Villiger reaction without significant loss of activity. Several factors, such as the partial solubility of KHSO5 in the ionic liquid, its viscosity and the presence of a proton in protic ionic liquids, have an influence on the course of the reaction.
- Chrobok, Anna
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experimental part
p. 6212 - 6216
(2010/09/15)
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- A novel one-step method for the reductive allylation of esters and the first total synthesis of (±)-erythrococcamide B
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A novel and convenient one-step method for the reductive allylation of aliphatic and alicyclic esters using InBr3 as a catalyst is reported. This methodology has also been applied in the first total synthesis of (±)-erythrococcamide B.
- Lagoutte, Roman,Wilkinson, James A.
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experimental part
p. 6942 - 6944
(2011/03/18)
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- Direct oxidative cyclization of 3-arylpropionic acids using PIFA or Oxone: synthesis of 3,4-dihydrocoumarins
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The direct oxidative cyclization of 3-arylpropionic acids using PIFA or Oxone is reported. In the presence of BF3·OEt2, the reaction of 3-arylpropionic acids with PIFA or Oxone proceeded smoothly at 30 °C to give 3,4-dihydrocoumarins
- Gu, Yonghong,Xue, Kun
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supporting information; experimental part
p. 192 - 196
(2010/03/04)
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- Rhodium(I)-catalyzed enantioselective 1,4-addition of nucleophilic silicon
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A rhodium(I)-catalyzed activation of a silicon-boron linkage, that is, the transmetalation of silicon from boron to rhodium(I) by means of an RhI-OH complex, enables the conjugate transfer of nucleophilic silicon onto α,β-unsaturated acceptors. Pre- or in situ formed cationic rhodium(I)-binap complexes catalyze this novel carbon-silicon bond formation with exceptional enantiocontrol, 92 to >99% ee for cyclic carbonyl and carboxyl compounds as well as >99% ee for acyclic carboxyl compounds.
- Walter, Christian,Fr?hlich, Roland,Oestreich, Martin
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experimental part
p. 5513 - 5520
(2009/12/09)
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- Enzymatic Baeyer-Villiger oxidation of Benzo-Fused ketones: Formation of regiocomplementary lactones
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Baeyer-Villiger monooxygenases (BVMOs) are enzymes that are known to catalyse the Baeyer-Villiger oxidation of ketones in aqueous media using O2 as oxidant. Herein, we describe the oxidation of a set of diverse benzo-fused ketones by three different BVMOs
- Rioz-Martinez, Ana,De Gonzalo,Torres Pazmino, Daniel E.,Fraaije, Marco W.,Gotor, Vicente
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supporting information; experimental part
p. 2526 - 2532
(2009/09/25)
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- Efficient method for oxidation of ketones to esters with 4-aminoperoxybenzoic acid supported on silica gel
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4-Aminoperoxybenzoic acid supported on silica gel was found to be a versatile and efficient oxidant for the oxidation of ketones to esters. Copyright Taylor & Francis Group, LLC.
- Ghazanfari, Dadkhoda,Hashemi, Mohammed M.,Shahidi-Zandi, Mehdi
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p. 2037 - 2042
(2008/09/21)
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- Bargellini condensation of coumarins. Expeditious route to o-carboxyvinylphenoxyisobutyric acids and application to the synthesis of sesquiterpenes helianane, heliannuol A and heliannuol C
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The direct Bargellini condensation of coumarins involving reaction with chloroform and acetone in the presence of aqueous sodium hydroxide furnished o-carboxyvinylphenoxyisobutyric acids in good yields. The utility of this new useful protocol was demonstrated by the transformation of the three diesters 9b, 9f and 9g to the sesquiterpenes helianane 4, heliannuol A 2 and heliannuol C 3, respectively.
- Biswas, Bidyut,Sen, Prabir K.,Venkateswaran, Ramanathapuram V.
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p. 12026 - 12036
(2008/03/13)
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- A chemoselective hydrogenation of the olefinic bond of α,β- unsaturated carbonyl compounds in aqueous medium under microwave irradiation
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A microwave-assisted mild and ecofriendly catalytic transfer hydrogenation process was developed to reduce various α,β-unsaturated carbonyl compounds into the corresponding saturated carbonyl compounds in the presence of silica-supported palladium chloride as catalyst and a combination of MeOH/HCOOH/H2O (1:2:3) as hydrogen source within 22-55 minutes in moderate to excellent yields with 100% chemoselectivity.
- Sharma, Anuj,Kumar, Vinod,Sinha, Arun K.
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p. 354 - 360
(2007/10/03)
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- Solid-supported green synthesis of substituted hydrocinnamic esters by focused microwave irradiation
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An efficient chemoselective hydrogenation protocol for substituted cinnamic esters is developed for the synthesis in quantitative yield of corresponding bioactive dihydrocinnamic esters with solid-supported palladium chloride/ammonium formate (cat.) in HCOOH/H2O 1:2 as a hydrogenating agent under focused-microwave irradiation for 10 min.
- Kumar, Vinod,Sharma, Anuj,Sinha, Arun K.
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p. 483 - 495
(2007/10/03)
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- Stable isotope characterization of the ortho-oxygenated phenylpropanoids: Coumarin and melilotol
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The natural abundance 2H NMR spectra of extractive coumarin 10 and of its dihydroderivative melilotol 11 produced by baker's yeast reduction has been compared with synthetic materials. Diagnostic for the differentiation of 10 are the (D/H)β values, which are in the 128.1-133.6 ppm interval for the natural compounds but 258.5 and 189.8 ppm for the synthetic materials. Such a dramatic difference is also found for methyl cinnamate 12, which shows (D/H)β values of 127.2 and 515.8 ppm, respectively. In extractive 10, the ratio (D/H)4(para)/(D/H)6(ortho) = 1.24 is similar to that observed in structurally related salicin and methyl salicylate. Coumarin 10 is transformed in salicyl alcohol 9, providing diacetate 14, showing in the natural series the trend (D/H)3(meta) > (D/H)4(para) > (D/H)5(meta) ~ (D/H) 6(ortho). A similar trend is shown also by the synthetic 10. A clear distinction between extractive and synthetic 10 is obtained through δ18O determinations on 10 and on chroman 13. The bulk δ18O values in the extractive series of 10 are 20.3, 23.6, and 22.6‰, while those of the aromatic oxygen are 2.3, 0.5, and -0.5‰. In the synthetic sample, the values are 12.6 and 5.6‰, respectively. As a final product, the reduction of 10 leads to the dihydroderivative 11. Both the baker's yeast reduction and the catalytic hydrogenation lead to a marked decrease of the deuterium content of 11, which is stronger for the β-position than for the α-position.
- Brenna, Elisabetta,Fronza, Giovanni,Fuganti, Claudio,Gatti, Francesco G.,Grande, Valentina,Serra, Stefano,Guillou, Claude,Reniero, Fabiano,Serra, Francesca
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p. 9383 - 9388
(2007/10/03)
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- Baeyer-Villiger oxidations in ionic liquids. A facile conversion of ketones to esters and lactones
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A variety of cyclic and acyclic ketones underwent readily oxidation with m-chloroperbenzoic acid (m-CPBA) in ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate [bmim]BF4 to afford esters/lactones with high selectivity, ease of product separation and in excellent chemical yields. The reaction proceeded smoothly in ionic liquid without the need of any additional acid or base catalyst. The ketones show enhanced reactivity in ionic liquids thereby reducing reaction times and improving the yields significantly.
- Yadav,Reddy,Basak,Narsaiah
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p. 248 - 249
(2007/10/03)
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- Selective oxidation of aryl ketones to α-diketones with 4-aminoperoxybenzoic acid supported on silica gel in presence of air
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4-Aminoperoxybenzoic acid supported on silica gel in presence of air was found to be a selective and convenient oxidant for the oxidation of methylene groups in aryl ketones to convert them to α-diketones. Springer-Verlag 2004.
- Ghazanfari, Dadkhoda,Najafizadeh, Fariba,Khosravi, Fereshteh
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p. 1409 - 1413
(2007/10/03)
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- Chemoselective reduction of α, β-unsaturated carbonyl compounds by sodium hydrogen telluride: Part I
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Sodium Hydrogen Telluride is used for the selective reduction of C=C bonds in various chalcones. The reduction proceeds smoothly in good yields.
- Geethamalika,Suguna Sundari,Shanmugam,Rajendran
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p. 674 - 676
(2007/10/03)
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- Cerium(III) bromate as a new reagent in oxidation of organic compounds
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Cerium(III) bromate, prepared by the reaction of barium bromate with cerium(III) sulfate, can be used for the oxidation of alkylarenes, alcohols, and sulfides. Products are obtained in high yields under mild conditions. Ce(BrO3)3 is an unique, dual property reagent in which the anion is the oxidant and the cation a catalyst. Stoichiometric studies indicate that bromate is reduced to bromide under these conditions, making the process highly efficient.
- Shaabani, Ahmad,Lee, Donald G.
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p. 1845 - 1854
(2007/10/03)
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- Mild and chemoselective synthesis of lactones from diols using a novel metal-ligand bifunctional catalyst.
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[reaction: see text] A novel amino alcohol-based Ir bifunctional complex acts as an efficient catalyst for oxidative lactonization of 1,4- or 1,5-diols with a substrate-to-catalyst molar ratio of 200-1000 in acetone or butanone. The reaction proceeds with broad functional group tolerance to give lactone in high yield at room temperature. The catalyst precursor Cp*IrCl[OCH(2)C(C(6)H(5))(2)NH(2)] is isolated and characterized by a single-crystal X-ray analysis.
- Suzuki, Takeyuki,Morita, Kenji,Tsuchida, Mika,Hiroi, Kunio
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p. 2361 - 2363
(2007/10/03)
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- Efficient and scaleable methods for ω-functionalized nonanoic acids: Development of a novel process for azelaic and 9-aminononanoic acids (nylon-6,9 and nylon-9 precursors)
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A new, convergent synthesis and process of the title open-chain C-9 compounds, valuable monomers for preparation of polyamides with specific properties, are discussed. Starting from relatively inexpensive raw materials, for example, cyclohexanone and activated C-3 olefins, the method provides polymer grade co-functionalized nonanoic acids. An improved protocol for cyanoethylation or carbalkoxyethylation of cyclohexanone in the presence of a catalytic amount of primary or secondary amines gave 3-(2-oxo-cyclohexane) propanecarboxylic acid derivatives 1 in high yield. Cyclohexaneperoxycarboxylic acid (CHPCA) is introduced as highly efficient reagent in Baeyer-Villiger rearrangement of 1. Pyrolysis of 2 (EWG = CN) afforded under optimized conditions 3 in high yield and regioisomeric purity, otherwise a mixture of three unsaturated isomeric ω-cyano nonenoic acids is obtained. Partial hydrogenation of unsaturated acids 3 allowed isolation of saturated long-chain difunctionalized acids 4. Hydrolysis of 4 led to 1,9-nonanedicarboxylic acid (azelaic acid) 5, whereas its hydrogenation at elevated pressure gave 9-aminononanoic acid 6. Alternatively, a practical four-step syntehsis of 5 via isolable 7-substituted oxepan-2-one (EWG = COOMe) 2 has been designed and experimentated. The versatile position of 3-(2-oxo-cyclohexane) propanecarboxylic acid derivatives 1 as raw materials for Fine Chemicals is also discussed.
- Cotarca, Livius,Delogu, Pietro,Nardelli, Alfonso,Maggioni, Paolo,Bianchini, Roberto,Sguassero, Stefano,Alini, Stefano,Dario, Roberto,Clauti, Giuliano,Pitta, Giorgio,Duse, Gianpaolo,Goffredi, Fabrizio
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- Regioselective intramolecular oxidation of phenols and anisoles by dioxiranes generated in situ
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A novel method for regioselective oxidation of phenols and anisoles has been developed in which dioxiranes, generated in situ from ketones and Ozone, oxidize phenol derivatives in an intramolecular fashion. A series of ketones with electron-withdrawing groups, such as CF3, COOMe, and CH2Cl, were attached to phenols, anisoles, or aryl rings via a C2 or C3 methylene linker. In a homogeneous solvent system of CH3CN and H2O, oxidation of phenol derivatives 1-10 afforded spiro 2-hydroxydienones in 24-55% yields regardless of the presence of other substituents (ortho Me, meta Me or Br) on the aryl ring and the length of the linker. Experimental evidences were provided to support the mechanism that involves a regioselective π bond epoxidation of aryl rings followed by epoxide rearrangement and hemiketal formation.
- Yang, Dan,Wong, Man-Kin,Yan, Zheng
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p. 4179 - 4184
(2007/10/03)
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