49642-47-9Relevant articles and documents
Substrate-modifier but not catalyst-modifier: Heterogeneous hydrogenation of C=O and C=C using cinchonidine
Solladié-Cavallo,Marsol,Hoernel,Garin
, p. 4741 - 4744 (2001)
Literature results and our own, concerning hydrogenation of ethyl pyruvate and 2-methyl pentenoic acid over Al2O3-supported platinum and palladium using cinchonidine (CD), indicate that CD activates pyruvate (through enol formation) and modifies the unsaturated acid (salt formation), but not the catalyst, and that CD may even poison the catalyst (palladium more than platinum). Therefore, the modifier's properties must fit the substrate's properties and not be a catalyst poison, the best sequence for addition of the reactants being: first a mixture of substrate/CD and then the supported Pt and/or Pd catalyst.
Resolution of racemic acids by irreversible lipase-catalyzed esterification in organic solvents
Morrone, Raffaele,Piattelli, Mario,Nicolosi, Giovanni
, p. 1441 - 1443 (2001)
The reversible nature of the direct esterification of acids with alcohols limits the use of this process in the biocatalytic kinetic resolution of chiral acids. A new irreversible procedure, using orthoesters, has been developed.
Enantioselective rearrangement coupled with water addition: Direct synthesis of enantiomerically pure saturated carboxylic acids from α,β-unsaturated aldehydes
Winkler, Till,Groeger, Harald,Hummel, Werner
, p. 961 - 964 (2014/05/06)
A novel type of organic synthesis enabling a direct one-pot transformation of α,β-unsaturated aldehydes into saturated carboxylic acids is described. As sole reagent water is required, which is integrated completely in the product. This tandem process proceeds under perfect atom economy, and consists of two coupled redox biotransformations without the need of external co-substrates for cofactor regeneration. The initial reduction of the C=C double bond of an α,β-unsaturated aldehyde is catalyzed by an NADPH-dependent ene reductase, leading to the formation of the saturated aldehyde and NADP+. The aldehyde intermediate is then oxidized to the corresponding carboxylic acid, thus regenerating NADPH for the next catalytic cycle. When using prochiral α,β-unsaturated aldehydes as substrates the corresponding carboxylic acids are formed enantioselectively with up to >99 % ee as demonstrated, e.g., for the transformation of citral to (S)-citronellic acid. Making a splash with citral: The direct one-pot transformation of α,β-unsaturated aldehydes to saturated carboxylic acids using only water proceeds with perfect atom economy. This tandem process involves two redox biotransformations without need of additional external co-substrates for cofactor regeneration. With, for example, citral as prochiral α,β-unsaturated aldehyde, transformation to (S)-citronellic acid proceeds with >99 % conversion and >99 % ee.
Enantioselective hydrogenation of α,β-unsaturated carboxylic acid over cinchonidine-modified Pd nanoparticles confined in carbon nanotubes
Guan, Zaihong,Lu, Shengmei,Li, Can
, p. 1 - 5 (2014/01/06)
We report the enantioselective hydrogenation of α,β-unsaturated acid catalyzed by Pd nanoparticles in carbon nanotubes (CNTs) taking the advantage of the channels as nanoreactors. The Pd nanocatalyst inside the channels of CNTs shows higher activity and e
Enantioselective hydrogenation of α,β-unsaturated carboxylic acids on Pd nanocubes
Chen, Chunhui,Zhan, Ensheng,Ta, Na,Li, Yong,Shen, Wenjie
, p. 2620 - 2626 (2013/09/24)
Pd nanocubes of 6-19 nm in size were synthesized using a seeded growth method and examined for enantioselective hydrogenation of α,β- unsaturated carboxylic acids. It was found that the Pd nanocubes had two types of active sites on the planes and at the edges, respectively. Small nanocubes having a higher edge/plane ratio were more active in enantioselective hydrogenation of α,β-unsaturated carboxylic acids, but afforded a lower enantioselectivity because their sharp edges could not offer stable adsorption of the chiral modifier and the reaction intermediates. In contrast, large nanocubes with a higher fraction of flat planes provided a higher enantioselectivity but a much lower activity.
Efficient cluster-based catalysts for asymmetric hydrogenation of α-unsaturated carboxylic acids
Moberg, Viktor,Duquesne, Robin,Roehrs, Oliver,Nachtigall, Jonny,Nordlander, Ebbe,Contaldi, Simone,Monari, Magda,Damoense, Llewellyn,Green, Michael,Hutton, Alan T.,Santelia, Daniela,Haukka, Matti
, p. 12458 - 12478,21 (2020/08/24)
The new clusters [H4Ru4(CO)10(μ-1,2-P- P)], [H4Ru4(CO)10(1,1-P-P)] and [H 4Ru4(CO)11(P-P)] (P-P=chiral diphosphine of the ferrocene-based Josiphos or Walphos ligand families) have been synthesised and characterised. The crystal and molecular structures of eleven clusters reveal that the coordination modes of the diphosphine in the [H4Ru 4(CO)10(μ-1,2-P-P)] clusters are different for the Josiphos and the Walphos ligands. The Josiphos ligands bridge a metal-metal bond of the ruthenium tetrahedron in the "conventional" manner, that is, with both phosphine moieties coordinated in equatorial positions relative to a triangular face of the tetrahedron, whereas the phosphine moieties of the Walphos ligands coordinate in one axial and one equatorial position. The differences in the ligand size and the coordination mode between the two types of ligands appear to be reflected in a relative propensity for isomerisation; in solution, the [H4Ru4(CO)10(1,1-Walphos)] clusters isomerise to the corresponding [H4Ru4(CO) 10(μ-1,2-Walphos)] clusters, whereas the Josiphos-containing clusters show no tendency to isomerisation in solution. The clusters have been tested as catalysts for asymmetric hydrogenation of four prochiral α-unsaturated carboxylic acids and the prochiral methyl ester (E)-methyl 2-methylbut-2-enoate. High conversion rates (>94 %) and selectivities of product formation were observed for almost all catalysts/catalyst precursors. The observed enantioselectivities were low or nonexistent for the Josiphos-containing clusters and catalyst (cluster) recovery was low, suggesting that cluster fragmentation takes place. On the other hand, excellent conversion rates (99-100 %), product selectivities (99-100 % in most cases) and good enantioselectivities, reaching 90 % enantiomeric excess (ee) in certain cases, were observed for the Walphos-containing clusters, and the clusters could be recovered in good yield after completed catalysis. Results from high-pressure NMR and IR studies, catalyst poisoning tests and comparison of catalytic properties of two [H4Ru4(CO)10(μ-1,2-P-P)] clusters (P-P=Walphos ligands) with the analogous mononuclear catalysts [Ru(P-P)(carboxylato)2] suggest that these clusters may be the active catalytic species, or direct precursors of an active catalytic cluster species. Copyright
Synthesis and absolute configuration of (S)-(+)-chichimol ketone: the defensive secretion of walking stick Agathemera elegans
Espinoza-Moraga, Marlene,Cornejo-Morales, Roxana,Santos, Leonardo Silva
body text, p. 1062 - 1064 (2009/09/30)
The first enantioselective synthesis of chichimol ketone (4-methyl-1-hepten-3-one) is described and the absolute configuration of the main semiochemical compound is determined as having an (S)-configuration. The synthesis features the use of a ruthenium c
Highly efficient asymmetric hydrogenation of α,β-unsaturated carboxylic acids catalyzed by ruthenium(II)-dipyridylphosphine complexes
Qiu, Liqin,Li, Yue-Ming,Kwong, Fuk Yee,Yu, Wing-Yiu,Fan, Qing-Hua,Chan, Albert S. C.
, p. 517 - 520 (2008/02/08)
Two types of catalysts [RuL(benzene)Cl]Cl and Ru(OCOCH3) 2L with the dipyridylphosphine ligands P-Phos and Xyl-P-Phos were applied in the asymmetric hydrogenation of α,β-unsaturated carboxylic acids. The cationic complexes [RuL(benzene)Cl]Cl were found to be superior to the corresponding neutral complex Ru(OCOCH3)2L in this type of reactions. The catalysts exhibited excellent activities and enantioselectivities (up to 97% ee) in the asymmetric hydrogenation.
Enantiomeric partitioning using fluorous biphase methodology for lipase-mediated (trans)esterifications
Beier, Petr,O'Hagan, David
, p. 1680 - 1681 (2007/10/03)
Lipase-catalysed (trans)esterification reactions in homogenous perfluorocarbon-hydrocarbon solvents enabled direct enantiomeric partitioning (up to 95% ee) of the products by liquid-liquid separation.
Mutation of cysteine-295 to alanine in secondary alcohol dehydrogenase from thermoanaerobacter ethanolicus affects the enantioselectivity and substrate specificity of ketone reductions
Heiss, Christian,Laivenieks, Maris,Zeikus,Phillips, Robert S.
, p. 1659 - 1666 (2007/10/03)
The mutation of Cys-295 to alanine in Thermoanaerobacter ethanolicus secondary alcohol dehycrogenase (SADH) was performed to give C295A SADH, on the basis of molecular modeling studies utilizing the X-ray crystal structure coordinates of the highly homologous T. brockii secondary alcohol dehydrogenase (YKF.PDB). This mutant SADH has activity for 2-propanol comparable to wild-type SADH. However, the C295A mutation was found to cause a significant shift of enantioselectivity toward the (S)-configuration in the reduction of some ethynylketones to the corresponding chiral propargyl alcohols. This result confirms our prediction that Cys-295 is part of a small alkyl group binding pocket whose size determines the binding orientation of ketone substrates, and, hence, the stereochemical configuration of the product alcohol. Furthermore, C295A SADH has much higher actifity towards t-butyl and some α-branched ketones than does wild-type SADH. The C295A mutation does not affect the thioester reductase activity of SADH. The broader substrate specificity and altered stereoselectivity for C295A SADH make it a potentially useful tool for asymmetric reductions. Copyright
