Stereochemistry of imino-group reduction. Part 3. The hydride reduction of achiral benzil monoimines

Abstract

The RR,SS:RS,SR ratio of diastereoisomeric amino-alcohols obtained from the lithium aluminium hydride reduction of the monoimines prepared by reaction of benzil and various aliphatic and aromatic achiral amines has been determined. Stereochemical results are analysed in terms of competition between two reaction routes involving respectively preliminary reduction of the oxo group and the imino group. The influence of polar and steric factors of the nitrogen substituent is discussed as is also that of solvent polarity. The reduction of some monoimines with sodium borohydride has also been studied. An interpretation of the ratios RR,SS:RS,SR is provided.