Copper-Catalyzed Decarboxylative Cascade Annulation of Propargylic Cyclic Carbamates with Allenediones

A copper-catalyzed decarboxylative cascade annulation reaction of 5-ethynyloxazolidine-2,4-diones and allenediones has been developed. This protocol affords a new class of pyranofuran derivatives in moderate to high yields with good Z/E selectivity. A proposed mechanism indicated that the reaction undergoes a cascade [4+1] annulation/intramolecular cyclization reaction. This cascade process underscores the promising potential of copper-allenylidenes in the construction of complex fused ring systems through cascade annulation.