- Overcoming Selectivity Issues in Reversible Catalysis: A Transfer Hydrocyanation Exhibiting High Kinetic Control
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Reversible catalytic reactions operate under thermodynamic control, and thus, establishing a selective catalytic system poses a considerable challenge. Herein, we report a reversible transfer hydrocyanation protocol that exhibits high selectivity for the thermodynamically less favorable branched isomer. Selectivity is achieved by exploiting the lower barrier for C-CN oxidative addition and reductive elimination at benzylic positions in the absence of a cocatalytic Lewis acid. Through the design of a novel type of HCN donor, a practical, branched-selective, HCN-free transfer hydrocyanation was realized. The synthetically useful resolution of a mixture of branched and linear nitrile isomers was also demonstrated to underline the value of reversible and selective transfer reactions. In a broader context, this work demonstrates that high kinetic selectivity can be achieved in reversible transfer reactions, thus opening new horizons for their synthetic applications.
- Bhawal, Benjamin N.,Ehinger, Christian,Morandi, Bill,Reisenbauer, Julia C.
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supporting information
p. 10914 - 10920
(2020/07/13)
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- One methyl group makes a major difference: Shape-selective catalysis by zeolite nanoreactors in liquid-phase condensation reactions
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The precise sizes of zeolites' micropores can induce sharp shape/size-selectivity with precision of less than 1 ? in gas-phase reactions, e.g. methanol to olefin reactions (MTO). However, it is still a major challenge and an unachieved task in liquid-phas
- Liu, Chang,Cao, Changyan,Liu, Jian,Wang, Xiaoshi,Zhu, Yanan,Song, Weiguo
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p. 17464 - 17469
(2017/09/01)
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- Sterically Demanding Oxidative Amidation of α-Substituted Malononitriles with Amines Using O2
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An efficient amidation method between readily available 1,1-dicyanoalkanes and either chiral or nonchiral amines was realized simply with molecular oxygen and a carbonate base. This oxidative protocol can be applied to both sterically and electronically challenging substrates in a highly chemoselective, practical, and rapid manner. The use of cyclopropyl and thioether substrates support the radical formation of α-peroxy malononitrile species, which can cyclize to dioxiranes that can monooxygenate malononitrile α-carbanions to afford activated acyl cyanides capable of reacting with amine nucleophiles.
- Li, Jing,Lear, Martin J.,Hayashi, Yujiro
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p. 9060 - 9064
(2016/07/26)
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- One-pot multistep cascade reactions over multifunctional nanocomposites with pd nanoparticles supported on amine-modified mesoporous silica
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Two kinds of multifunctional nanocomposites, SBA-15-NH2/Pd-p and SBA-15-NH2/Pd-f, with platelet-like and fiber-like morphologies, respectively, were fabricated by immobilizing Pd NPs onto amine-functionalized SBA-15. Some of the amino groups acted as anchoring sites for Pd NPs, whilst the remaining groups acted as Bronsted basic sites. As a result, the composites served as excellent multifunctional heterogeneous catalysts for one-pot multistep cascade reaction sequences. Moreover,when diffusion was the rate-determine step, SBA-15-NH2/Pd-p, with small mesopores, was superior to the fiber-like control sample, owing to its short diffusion length, a lower possibility of pore clogging, and better mass transportation for the reaction species during the catalysis.
- Li, Ping,Liu, Hua,Yu, Yu,Cao, Chang-Yan,Song, Wei-Guo
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p. 2459 - 2465
(2013/10/08)
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- Synthetic and mechanistic studies of metal-free transfer hydrogenations applying polarized olefins as hydrogen acceptors and amine borane adducts as hydrogen donors
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Metal-free transfer hydrogenation of polarized olefins (RR′ CCEE′: R, R′ = H or organyl, E, E′ = CN or CO2Me) using amine borane adducts RR′NH-BH3 (R = R′ = H, AB; R = Me, R′ = H, MAB; R = tBu, R′ = H, tBAB; R = R′ = Me, DMAB) as hydrogen donors, were studied by means of in situ NMR spectroscopy. Deuterium kinetic isotope effects and the traced hydroboration intermediate revealed that the double H transfer process occurred regio-specifically in two steps with hydride before proton transfer characteristics. Studies on substituent effects and Hammett correlation indicated that the rate determining step of the HN transfer is in agreement with a concerted transition state. The very reactive intermediate [NH2BH2] generated from AB was trapped by addition of cyclohexene into the reaction mixture forming Cy2BNH2. The final product borazine (BHNH)3 is assumed to be formed by dehydrocoupling of [NH2BH2] or its solvent stabilized derivative [NH2BH2]-(solvent), rather than by dehydrogenation of cyclotriborazane (BH2NH 2)3 which is the trimerization product of [NH 2BH2].
- Yang, Xianghua,Fox, Thomas,Berke, Heinz
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experimental part
p. 852 - 860
(2012/02/05)
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- Facile metal free regioselective transfer hydrogenation of polarized olefins with ammonia borane
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Transfer hydrogenation of polarized olefins bearing strongly electron-withdrawing groups on one side of the double bond was achieved with ammonia borane under mild conditions without using a catalyst. Mechanistic studies proved the character of the direct H transfers proceeding stepwise with a unique hydroboration intermediate and hydride before proton transfer.
- Yang, Xianghua,Fox, Thomas,Berke, Heinz
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p. 2053 - 2055
(2011/03/22)
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- Rh-catalyzed one-pot reductive alkylation of malononitrile under transfer hydrogenation conditions
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Efficient synthesis of monosubstituted malononitriles was achieved by one-pot reductive alkylation of malononitrile with carbonyl compounds via [Cp*RhCl2]2-catalyzed transfer hydrogenation reaction.
- Wu, Jiashou,Jiang, Huajiang
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experimental part
p. 1218 - 1226
(2011/05/04)
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- Development of pharmaceutical drugs, drug intermediates and ingredients by using direct organo-click reactions
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Here we report on our studies of the use of combinations of amino acids, amines, K2CO3 or Cs2CO3 and CuSO4/Cu for catalysing green cascade reactions. We aimed to prepare the highly reactive and substituted olefin species 7 and 8, under very mild and environmentally friendly conditions, thus giving the hydrogenated products 10 and 12 through the action of Hantzsch ester (4) by self-catalysis through decreasing the HOMO-LUMO energy gaps between olefins 7/8 and Hantzsch ester (4) through biomimetic reductions. Highly useful compounds 10 to 14 were assembled from simple substrates such as aldehydes 1, ketones 2, CH acids 3, Hantzsch ester (4) and alkyl halides 5 by diversity-oriented green synthesis involving cascade olefination/hydrogenation (O/H), olefination/hydrogenation/alkylation (O/H/A) and hydrogenation/olefination/hydrogenation (H/O/H) reaction sequences in one-pot fashion with stereospecific organo- and organo-/metal-carbonate catalysis. Highly functionalized diverse compounds such as 10 to 14 are biologically active products and have found wide applications as pharmaceutical drugs, drug intermediates and drug ingredients. For the first time in organocatalysis, we report the O/H/A/TE reaction to furnish high yields of transesterification products 11 by simply mixing the reactants under proline/K2CO3 catalysis conditions. Additionally, a novel organocatalytic H/O/H reaction sequence for the synthesis of alkyl-substituted aromatics has been developed. Furthermore, for the first time we have developed organocatalysed cascade olefination/hydrogenation/hydrolysis (O/H/H) reactions to furnish highly useful materials such as 2-oxochroman-3-carboxylic acid (14kc) and 2-amino-4H-chromene-3-carbonitrile (14kj) in good yields. Experimentally simple and environmentally friendly organocatalytic two-carbon homologation through cascade O/H/H reactions of aldehydes 1, Meldrum's acid (3c), Hantzsch ester (4) and acetic acid/triethylamine in ethanol has been demonstrated. Additionally, we have developed a green synthesis of the highly substituted 1,2,3-triazole 17 from simple substrates through a two-step combination of olefination/hydrogenation/alkylation and Huisgen cycloaddition reaction sequences under stereospecific organocopper catalysis conditions. In this paper we have found strong support for our hypothesis that, "decreasing the HOMO-LUMO energy gap between olefins 7/8 and Hantzsch ester (4) will drive the biomimetic hydrogenation reaction by self-catalysis". This self-catalysis was further confirmed with many varieties of examples. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Ramachary, Dhevalapally B.,Kishor, Mamillapalli,Reddy, Y. Vijayendar
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supporting information; experimental part
p. 975 - 993
(2009/04/11)
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- 3-Butyl-1-methylimidazolinium borohydride ([bmim][BH4])-a novel reducing agent for the selective reduction of carbon-carbon double bonds in activated conjugated alkenes
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A novel ionic reducing reagent, 3-butyl-1-methylimidazolium borohydride ([bmim][BH4]), was synthesized and successfully used for the selective reduction of carbon-carbon double bonds in conjugated alkenes as well as the α,β-carbon-carbon double bonds in highly activated α,β,γ,δ-unsaturated alkenes. The reagent can be regenerated and reused several times without losing its activity.
- Wang, Jiayi,Song, Gonghua,Peng, Yanqing,Zhu, Yidong
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supporting information; scheme or table
p. 6518 - 6520
(2009/04/06)
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- Environmentally friendly one-pot synthesis of α-alkylated nitriles using hydrotalcite-supported metal species as multifunctional solid catalysts
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A ruthenium-grafted hydrotalcite (Ru/HT) and hydrotalcite-supported palladium nanoparticles (Pdnano/ HT) are easily prepared by treating basic layered double hydroxide, hydrotalcite (HT, Mg6Al 2(OH)16CO3) with aqueous RuCl 3·n H2O and K2[PdCl4] solutions, respectively, using surface impregnation methods. Analysis by means of X-ray diffraction, and energydispersive X-ray, electron paramagnetic resonance, and X-ray absorption fine structure spectroscopies proves that a monomeric RuIV species is grafted onto the surface of the HT. Meanwhile, after reduction of a surface-isolated PdII species, highly dispersed Pd nanoclusters with a mean diameter of about 70 A is observed on the Pdnano/HT surface by transmission electron microscopy analysis. These hydrotalcite-supported metal catalysts can effectively promote α-alkylation reactions of various nitriles with primary alcohols or carbonyl compounds through tandem reactions consisting of metal-catalyzed oxidation and reduction, and an aldol reaction promoted by the base sites of the HT. In these catalytic α-alkylations, homogeneous bases are unnecessary and the only by-product is water. Additionally, these catalyst systems are applicable to one-pot syntheses of glutaronitrile derivatives.
- Motokura, Ken,Fujita, Noriaki,Mori, Kohsuke,Mizugaki, Tomoo,Ebitani, Kohki,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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p. 8228 - 8239
(2007/10/03)
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- Development of drug intermediates by using direct organocatalytic multi-component reactions
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Development of drug intermediates by using direct amino acid organocatalytic multi-component reaction was investigated. Hydrogenations of double-bond containing compounds including carbonyls, imines and olefins are important for living organisms as well as for the industrial production of chemicals. Amino acid catalysis has emerged as a powerful green synthetic tool for the development of both achiral and chiral catalysis of condensations and cycloadditions and the 1,2- and 1,4-additions of enals, enones and ketones including electrophiles. It was found that the amino acid proline 4a catalyzes the Knoevenagel condenstion of cyclohexanone 1a with the CH-acid ethyl cyanoacetate 2a to furnish the active olefin 9aa. This simple and environmentally friendly approach can be used to construct highly substituted hydrogenated products in a regioselective fashion with good yields.
- Ramachary, Dhevalapally B.,Kishor,Reddy, G. Babul
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p. 1641 - 1646
(2008/02/03)
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- Sodium borohydride as the only reagent for the efficient reductive alkylation of malononitrile with ketones and aldehydes
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An efficient and convenient method for the synthesis of primary and secondary monosubstituted malononitriles has been developed. In this method, sodium borohydride in isopropanol has a catalytic effect on the initial condensation between malononitrile and
- Dunham, Jason C.,Richardson, Adam D.,Sammelson, Robert E.
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p. 680 - 686
(2007/10/03)
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- A convenient and selective one-pot method for the synthesis of monosubstituted secondary alkyl malononitriles
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We have found that α,α-dicyanoalkenes can be efficiently and selectively reduced to α,α-dicyanoalkanes (malononitriles) with NaBH4 in 95% EtOH at 0 °C. In addition, we have determined that the condensation of malononitrile with ketones using absorption alumina as a catalyst can be followed directly, in one pot, by reduction with NaBH 4 in 95% EtOH at 0 °C to provide the monosubstituted secondary alkyl malononitriles in good to excellent yields (42-94%). This procedure provides a convenient alternative to direct alkylation of malononitrile or reduction of α,α-dicyanoalkene intermediates.
- Sammelson, Robert E.,Allen, Mark J.
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p. 543 - 546
(2007/10/03)
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- One-pot synthesis of α-alkylated nitriles with carbonyl compounds through consecutive aldol reaction/hydrogenation using a hydrotalcite-supported palladium nanoparticle as a multifunctional heterogeneous catalyst
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α-Alkylation of various nitriles with carbonyl compounds successfully proceeded using a hydrotalcite-supported palladium nanoparticle as a multifunctional catalyst. The alkylated nitriles were formed through aldol reaction at base sites on the hydrotalcite surface followed by hydrogenation by molecular hydrogen on the palladium nanoparticle.
- Motokura, Ken,Fujita, Noriaki,Mori, Kohsuke,Mizugaki, Tomoo,Ebitani, Kohki,Kaneda, Kiyotomi
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p. 5507 - 5510
(2007/10/03)
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- Reduction of activated conjugated alkenes by the InCl3-NaBH 4 reagent system
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A combination of a catalytic amount of indium (III) chloride and sodium borohydride in acetonitrile reduces selectively the carbon-carbon double bonds in conjugated alkenes such as α,α-dicyano olefins, α,β-unsaturated nitriles, cyanoesters, cyanophosphonate and dicarboxylic esters. However, reduction of chalcones is little different. They are reduced to a mixture of saturated ketones and alcohols if the reaction mixture is quenched with H2O, whereas quenching with MeOH leads to saturated alcohols only.
- Ranu, Brindaban C.,Samanta, Sampak
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p. 7901 - 7906
(2007/10/03)
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- Use of indium hydride (Cl2InH) for chemoselective reduction of the carbon-carbon double bond in conjugated alkenes
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Indium hydride (Cl2InH) generated in situ from a combination of a catalytic amount of indium(III) chloride and sodium borohydride selectively reduces the carbon-carbon double bond in conjugated alkenes such as α,α-dicyano olefins, α,β-unsaturated nitriles, cyano esters, cyanophosphonate, diesters and ketones.
- Ranu, Brindaban C.,Samanta, Sampak
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p. 7405 - 7407
(2007/10/03)
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- Indium metal as a reducing agent. Selective reduction of the carbon-carbon double bond in highly activated conjugated alkenes
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(Equation presented) Indium metal in aqueous ethanolic ammonium chloride reduces the C=C bond in highly activated conjugated alkenes such as α,α-dicyano olefins, β-arylenones, and enone esters.
- Ranu, Brindaban C.,Dutta, Jyotirmoy,Guchhait, Sankar K.
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p. 2603 - 2605
(2007/10/03)
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- Dual Regioselectivity in the Photoallylation of Electron-Deficient Alkenes by Allylic Silanes
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The photoreaction of 1-aryl-2,2-dicyanoethenes with allylic silanes in the presence of phenanthrene gave 4-aryl-5,5-dicyano-1-pentenes in high yields.In this photoreaction, the allylic groups were introduced regioselectively at the β-position to cyano gro
- Mizuno, Kazuhiko,Ikeda, Munehiro,Otsuji, Yoshio
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p. 1507 - 1510
(2007/10/02)
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- Electro-organic Reactions. Part 26. The Cathodic Reduction of Dicyanoethylene Derivatives; Competition between Hydrogenation and Hydrodimerisation
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Dicyanoethylene derivatives, and related compounds, undergo smooth cathodic reduction to give the products of hydrogenation (2 F mol-1), hydrodimerisation (1 F mol-1), or a mixture of both.The product distribution depends crucially u
- Clarke, Norman C.,Runciman, Peter J. I.,Utley, James H. P.,Landquist, Justus K.
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p. 435 - 440
(2007/10/02)
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- In Situ Generation and Synthetic Application of 2-Phenylbenzimidazoline to the Selective Reduction of Carbon-Carbon Double Bonds of Electron-Deficient Olefins
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2-Phenylbenzimidazoline (PBI) as a mild, selective, and convenient reducing agent was efficiently generated in situ from o-phenylenediamine and benzaldehyde in alcohols.A generally applicable method for the selective reduction of carbon-carbon double bonds of a variety of electron-deficient olefins with an alcoholic solution of PBI is described.The reduction of α,β-unsaturated ketones to the corresponding saturated ketones could also be accomplished (but, less effectively) with PBI with the aid of a Lewis-acid catalyst. 1-Methyl-2-(o-nitrophenyl)benzimidazoline prepared and isolated by the reaction of o-nitrobenzaldehyde with N-methyl-o-phenylenediamine reduced benzylidenemalononitrile to give benzylmalononitrile and 1-methyl-2-(o-nitrophenyl)benzimidazoline in high yields.This shows the validity of PBI to be the actual reducing species in the present reduction system.From a mechanistic study, the present reductions could be interpreted in terms of a mechanism involving a synchronous transport of a pair of hydrogens or a sequential transfer of a hydride and a proton from PBI to the olefins.
- Chikashita, Hidenori,Nishida, Shuichi,Miyazaki, Makoto,Morita, Yasuhiro,Itoh, Kazuyoshi
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p. 737 - 746
(2007/10/02)
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