Chiral Phosphine Catalyzed Allylic Alkylation of Benzylidene Succinimides with Morita-Baylis-Hillman Carbonates

Owing to their unique chemical properties, alpha-alkylidene succinimides generally act as versatile synthons in organic synthesis. Compared with well-established annulations, nucleophilic alkylations of alpha-alkylidene succinimides are very limited. Accordingly, an organocatalytic allylic alkylation of alpha-benzylidene succinimides with Morita-Baylis-Hillman (MBH) carbonates was established. In the presence of a chiral phosphine catalyst, alpha-benzylidene succinimides reacted smoothly with MBH carbonates under mild conditions to furnish a series of optical active succinimides in high yields and enantioselectivities. Different from the reported results, the organocatalytic enantioselective construction of pyrrolidine-2,5-dione frameworks bearing contiguous chiral tertiary carbon centers was achieved via this synthetic strategy. Scaling up the reaction indicated that it is a practical strategy for the organocatalytic enantioselective alkylation of alpha-alkylidene succinimides. A possible reaction mechanism was also proposed.