X = Y - ZH systems as potential 1,3-dipoles. Part 40. Chiral azomethine ylides from homochiral cyclic α-amino esters. Unusual regiospecific deprotonation of iminium ions.

Abstract

A 1,3-Strain and charge accelerated 1,5-H shifts are important factors in the stereospecific formation of iminium ions from cyclic secondary α-amino esters and bifunctional carbonyl compounds and their regiospecific or regioselective conversion to homochiral azomethine ylides. The endo-exo selectivity in the cycloadditions of these azomethine ylides is sensitive to the bifunctional carbonyl compound employed.