Asymmetric synthesis using chirally modified borohydrides. Part 4. Enantio-selective reduction of ketones and oxime ethers with the reagent prepared from borane and polymer-supported (S)-(–)-2-amino-3-(p-hydroxyphenyl)-1,1-diphenylpropan-1-ol

Abstract

The polymer-supported chiral amino alcohol (3) has been prepared by the reaction of chloromethylated polystyrene resin and (S)-(–)-2-amino-3-(p-hydroxy)phenyl-1,1-diphenylpropan-1-ol (2); the chiral polymeric reagent has been prepared from (3) and borane. The asymmetric reductions of ketones and oxime ethers with the polymeric reagent have been shown to give optically active alcohols (up to 97% optical purity) and amines (up to 67% optical purity), respectively. The results are compared with those obtained with (S)-(–)-2-amino-1,1,3-triphenylpropan-1-ol (4) or (S)-(–)-2-amino-3-(p-benzyl-oxyphenyl)-1,1 -diphenylpropan-1-ol (5) which are soluble model reagents.