Stereochemistry of imino-group reduction. Part 6. Stereochemistry of reduction of 1,2-imino ketones having a pre-existing chiral centre. Synthesis of amino alcohols with three chiral centres

Abstract

Stereochemical results of the lithium aluminium hydride and sodium borohydride reduction of 1,2-imino ketones, PhCOCPhNCHRPh (R = Me, Et, Pr, Bu, Buⁱ, Prⁱ, Bu^t), are reported. The stereoselectivity is accounted for by competition between two possible reactions: that proceeding through previous reduction of the carbonyl group and that involving previous reduction of the imino group. The relative involvement of both reaction routes depends upon the nature of the reagent and the relative hard–soft character of both functional groups in the imino ketones. The influence of steric effects of the R groups is discussed.