Phosphine-Catalyzed Cascade [3+2] Cyclization-Allylic Alkylation, [2+2+1] Annulation, and [3+2] Cyclization Reactions between Allylic Carbonates and Enones

The phosphine-catalyzed annulations between Morita-Baylis-Hillman adduct carbonates and enones are reported. Under the catalysis of PBu3 (20 mol %), cascade [3 + 2] cyclization-allylic alkylation, [2 + 2 + 1] annulation, and [3 + 2] cyclization reactions chemoselectively occur depending on the substituent variation of both the carbonate and enone. These reactions provide efficient syntheses of highly functionalized cyclopentenes and cyclopentanes.