Phosphine-Catalyzed [4+2] Annulation of Allenoate with Sulfamate-Derived Cyclic 'mines: A Reaction Mode Involving γ′-Carbon of α-Substituted Allenoate

A phosphine-catalyzed [4 + 2] cycloaddition of cyclic alpha-substituted allenoates with sulfamate-derived cyclic imines has been reported. Using dibenzylphenylphosphine as the nucleophilic catalyst, the reaction worked efficiently to yield various fused multicyclic heterocyclic compounds in high yields with excellent diastereoselectivities. It undergoes a new reaction mode involving gamma'-carbon of alpha-substituted allenoate.