A chiral phenol–NHC ligand enabled the copper-catalyzed enantioselectiveconjugate reduction of α,β-unsaturatedesters. The phenol moiety of the chiral NHC ligand played a critical role in producing the enantiomerically enriched products. The catalyst worked well for various (Z)-isomer substrates. Opposite enantiomers were obtained from (Z)- and (E)-isomers, with a higher enantiomeric excess from the
synthesized. For the majority of the ligands, coordination yielded only a single diastereoisomer with full control of the absolute configuration on sulfur. The different iridium complexes have been used in the hydrogenation of various di, tri, and tetrasubstituted minimallyfunctionalizedolefins. Conversions and enantioselectivities are highly dependent on the ligand and substrate structure. Full conversions
Lipase catalysed kinetic resolutions of 3-aryl alkanoic acids
作者:Rebecca E. Deasy、Maude Brossat、Thomas S. Moody、Anita R. Maguire
DOI:10.1016/j.tetasy.2010.12.019
日期:2011.1
Hydrolase catalysed kinetic resolutions leading to a series of 3-aryl alkanoic acids (>= 94% ee) are described. Hydrolysis of the ethyl esters with a series of hydrolases was undertaken to identify biocatalysts that yield the corresponding acids with excellent enantiopurity in each case. Steric and electronic effects on the efficiency and enantioselectivity of the biocatalytic transformation were also explored. (C) 2011 Elsevier Ltd. All rights reserved.
Pyrrolidine‐Based P,O Ligands from Carbohydrates: Easily Accessible and Modular Ligands for the Ir‐Catalyzed Asymmetric Hydrogenation of Minimally Functionalized Olefins
作者:Pilar Elías‐Rodríguez、Carlota Borràs、Ana T. Carmona、Jorge Faiges、Inmaculada Robina、Oscar Pàmies、Montserrat Diéguez
DOI:10.1002/cctc.201801485
日期:2018.12.7
The potential of P,O‐iminosugar based ligands in the Ir‐catalyzed asymmetric hydrogenation of minimallyfunctionalizedolefins is presented. These new ligands were prepared from easily available carbohydrates (D‐mannose, D‐ribose and D‐arabinose). The stereochemical and polyfunctional diversity of carbohydrates allowed the modulation of the ligands, both from their electronic properties and the rigidity