Asymmetric synthesis by using the chirality of l-ephedrine. III. Reaction of N-(arylmethylideneamino)ephedrine with benzylmagnesium chloride and phenyllithium.

Abstract

Reaction of N-(benzylideneamino) ephedrine (II) with benzylmagnesium chloride gave N-(1, 2-dimethylethylamino) ephedrine (a mixture of III and IV). On the other hand, reaction of N-[(2-phenylethylidene) amino] ephedrine (VII) with phenyllithium gave IV. Hydrogenolysis of these products gave 1, 2-diphenylethylamine with 40% (S) and 91% (R) optical purity, respectively, and l-ephedrine used as a chiral auxiliary reagent was recovered. Reactions of N-(arylmethylideneamino) ephedrines (VIII and IX) with benzylmagnesium chloride gave chiral hydrazines (X and XI), and reactions with phenyllithium gave XII and XIII.