Quinine-derived thiourea promoted enantioselective Michael addition reactions of 3-substituted phthalides to maleimides

A highly diastereoselective and enantioselective Michael addition/desymmetrization reaction of maleimides with prochiral 3- substituted phthalides catalyzed by quinine-derived bifunctional thiourea was realized. A broad range of the 3,3′-disubstituted phthalides bearing vicinal quaternary-tertiary stereogenic centers were synthesized in moderate to good yields (up to 96%) with high diastereoselectivities (up to >19:1 dr) and enantioselectivities (up to 96:4 er).