Some observations on the asymmetric reductive alkylation of cyclic imides

Asymmetric reductive alkylation of malimides is an effective method for the synthesis of optically active N - substituted 5 - alkyl - 4 - benzyloxy - 2 - pyrrolidinones. In order to expand the scope of this method, a study on the reductive alkylation of cyclic imides has been undertaken. Factors affecting the reductive alkylation are discussed and some possible mechanisms are proposed to account for the results obtained. The present study reveals that 3 - substituted and 3,4- disubstituted succinimides are imides suitable for asymmetric reductive alkylation, while the reaction with 3,4 - unsubstituted succinimides led to very low yields. This notable substituent effect is tentatively attributed to the Thorpe - Ingold effect and /or reactive - rotamer effect proposed by Jung.