STEREOSELECTIVE SYNTHESIS OF VICINAL DIAMINES

alpha-Amino aldimines such as 1, which are readily accessible from amino acids, react with alkyllithium and -cerium compounds in a chelation-controlled manner to give the vicinal diamines 2 in optical yields of up to 90%. However, if the donor strength of the aldimine nitrogen atom is weakened by the electron-withdrawing tosyl group, the chelation effect is suppressed and reaction with Grignard reagents gives preferentially the stereoisomeric adducts with opposite relative configuration. Bn = benzyl.