Phosphine-Catalyzed Tandem Annulation of Allenylic Alcohols with 1,1-Dicyanoalkenes

The phosphine-catalyzed tandem annulation of allenylic alcohols with 1,1-dicyanoalkenes has been developed, giving various bicyclic tetrahydrocyclopentafuran derivatives in 40-89% yields with moderate to excellent diastereoselectivities. The fused ring was furnished through a sequential (3 + 2) annulation/nucleophilic addition reaction. The unusual nucleophilic addition of an alkoxide ion to a cyano group led to a formation of tetrahydrofuran ring having an imino substituent.