作者:Thomas C. Nugent、Mohamed El-Shazly、Vijay N. Wakchaure
DOI:10.1021/jo7021235
日期:2008.2.1
Reductive amination of prochiral unhindered 2-alkanones 1 with (R)- or (S)-alpha-MBA in the presence of Yb(OAc)(3) (50-110 mol %), Raney-Ni, and hydrogen (120 psi) results in increased diastereoselectivity for the amine products 2 (80-89% de) with good yield (80-87%). The increased de is based on comparison with the best previously reported de's when using (R)- or (S)-alpha-MBA, regardless of the strategy employed [stepwise (isolation of ketimines) or one-pot (reductive amination)], reducing agent examined, or achiral Lewis acid or Bronsted acid examined. An in situ cis- to trans-ketimine isomerization mechanism, promoted by Yb(OAC)(3), has been proposed to account for the observed increase in diastereoselectivity and suggests a new entry into the control of ketimine geometry.
A Simple Diastereoselective Synthesis of Chiral Nonracemic Aliphatic Amines
作者:G. V. Grishina、E. R. Luk’yanenko、A. A. Borisenko
DOI:10.1007/s11178-005-0248-1
日期:2005.6
An efficient procedure has been developed for the diastereoselective synthesis of chiral aliphatic amines (diastereoisomeric excess >96%) from (1S)-N-(1-methylethylidene)-1-phenylethylamine, i.e., Schiff base derived from the simplest ketone (acetone) and (1S)-1-phenylethylamine. The procedure includes successive lithiation, alkylation, and reduction and is characterized by high regioselectivity in the formation of alkylated syn-Z-imines. Hydride reduction of the prochiral C=N bond in the latter gives mainly optically active aliphatic amines with R configuration. All reactions are performed as a one-pot process without isolation of intermediate products.
开发了一种有效的方法,用于从 (1S)-N-(1-甲基亚乙基)-1-苯乙胺(即源自最简单的酮(丙酮)的席夫碱)非对映选择性合成手性脂肪胺(非对映异构体过量 >96%)和(1S)-1-苯乙胺。该过程包括连续的锂化、烷基化和还原,其特点是在烷基化顺式-Z-亚胺的形成中具有高区域选择性。后者的前手性 C=N 键的氢化物还原主要产生具有 R 构型的光学活性脂肪胺。所有反应均以一锅法进行,无需分离中间产物。