137993-38-5Relevant academic research and scientific papers
Investigation of lewis acid versus lewis base catalysis in asymmetric cyanohydrin synthesis
North, Michael,Omedes-Pujol, Marta,Williamson, Courtney
experimental part, p. 11367 - 11375 (2010/11/17)
The asymmetric addition of trimethylsilyl cyanide to aldehydes can be catalysed by Lewis acids and/or Lewis bases, which activate the aldehyde and trimethylsilyl cyanide, respectively. It is not always apparent from the structure of the catalyst whether Lewis acid or Lewis base catalysis predominates. To investigate this in the context of using salen complexes of titanium, vanadium and aluminium as catalysts, a Hammett analysis of asymmetric cyanohydrin synthesis was undertaken. When Lewis acid catalysis is dominant, a significantly positive reaction constant is observed, whereas reactions dominated by Lewis base catalysis give much smaller reaction constants. [{Ti(salen)O}2] was found to show the highest degree of Lewis acid catalysis, whereas two [VO(salen)X] (X = EtOSO3 or NCS) complexes both displayed lower degrees of Lewis acid catalysis. In the case of reactions catalysed by [{Al(salen)}2O] and triphenyl- phosphine oxide, a non-linear Ham- mett plot was observed, which is indicative of a change in mechanism with increasing Lewis base catalysis as the carbonyl compound becomes more electron-deficient. These results suggested that the aluminium complex/tri- phenylphosphine oxide catalyst system should also catalyse the asymmetric addition of trimethylsilyl cyanide to ke- tones and this was found to be the case.
Enzymatic kinetic resolution of racemic cyanohydrins via enantioselective acylation
Xu, Qing,Xie, Yongli,Geng, Xiaohong,Chen, Peiran
experimental part, p. 624 - 630 (2010/09/07)
Enzymatic kinetic resolution of a series of aromatic and aliphatic cyanohydrins in organic media has been investigated. The behavior of potential lipases, molecular sieves, acyl reagent, reaction temperature, and organic solvents on the kinetic resolution was studied. The influence of substrate structure, steric, and electronic nature and position of the aryl substituent on the enantioselectivity was discussed. Under the optimized reaction conditions, good enantioselectivity could be achieved for most of the investigated compounds. Specifically, substrates 1a, 1c, 1d, 1f, 1u could be resolved with the kinetic enantiomer ratio (E) higher than 200.
Kinetic resolution of cyanohydrins via enantioselective acylation catalyzed by lipase PS-30
Xu, Qing,Geng, Xiaohong,Chen, Peiran
scheme or table, p. 6440 - 6441 (2009/04/06)
By using lipase PS-30 as catalyst, the kinetic resolution of a series of racemic cyanohydrins has been achieved via enantioselective acylation. The values of kinetic enantiomeric ratio (E) reached up to 314. Substituent effect is also briefly discussed.
An R-selective hydroxynitrile lyase from Arabidopsis thaliana with an α/β-hydrolase fold
Andexer, Jennifer,Von Langermann, Jan,Mell, Annett,Bocola, Marco,Kragl, Udo,Eggert, Thorsten,Pohl, Martina
, p. 8679 - 8681 (2008/09/18)
Folding and selectivity: The noncyanogenic plant Arabidopsis thaliana contains a new hydroxynitrile lyase, which was cloned and characterized. This enzyme is readily available form a recombinant source, has a broad range of substrates, and enantioselectively transforms aliphatic and aromatic aldehydes as well as ketones into the corresponding R-cyanohydrins. (Chemical Equation Presented).
