Chiral N-substituted secondary 1,2-aminoalcohols have been developed for the enantioseparation of ortho-halomandelic acids (o-X-MAs) via diastereomeric salt formation. Two structural isomers, N-methyl-2-amino-1,2-diphenylethanol and N-benzyl-2-amino-2-phenylethanol, showed high separation abilities for o-X-MAs (X = Cl, Br, I). The chiral recognition mechanism was elucidated by crystallographic analysis
手性N取代仲 1,2-氨基醇已开发用于通过非对映体盐形成原卤扁桃酸 ( o -X-MA) 的对映体分离。两种结构异构体N-甲基-2-氨基-1,2-二苯基乙醇和N-苄基-2-氨基-2-苯基乙醇对o -X-MA(X = Cl、Br、I)表现出较高的分离能力。通过难溶盐的晶体学分析阐明了手性识别机制。拆分剂氮原子上的取代基和结晶溶剂的包含稳定了盐并增强了它们的分离能力。
Palladium-catalyzed asymmetric allylic alkylation of 1,3-diplienyl-2-propenyl acetate with the dimethyl malonate-BSA-LiOAc system has been successfully carried out in the presence of easily prepared new chiral amino-phosphinite ligands such as 3b and 3c to result in good yields and excellent enantioselectivities of up to 95%, e.e. (C) 2002 Published by Elsevier Science Ltd.
Diastereoselective Michael addition of 2H-2-oxo-1,4,2-oxaza phosphinanes to olefins
Diastereoselective Michael additions of 2-hydrogeno-2-oxo-1,4,2-oxazaphosphinanes to olefins were described. Phosphinopeptide compounds were obtained in very good yield (up to 90%) and diasteromeric excesses ranging from 26 to 78%. Crown Copyright (C) 2010 Published by Elsevier Ltd. All rights reserved.
New Catalysts for the Asymmetric Hydrosilylation of Ketones Discovered by Mass Spectrometry Screening
作者:Sulan Yao、Jun-Cai Meng、Gary Siuzdak、M. G. Finn
DOI:10.1021/jo026365e
日期:2003.4.1
A method for determining enantiomeric excess by mass spectrometry was employed to screen a family of chiral phosphite P,N-ligands for activity in the rhodium-catalyzed asymmetric hydro-silylation of ketones. The identification of an effective set of ligands was followed by preliminary studies of the reaction scope and mechanism. Asymmetric induction of 84-88% ee for larger-scale reactions was observed, which is close to the level of the best alternative catalysts previously discovered. The screening method was shown to be applicable to a variety of substrates without the need for special optimization.