Cu(I)-Catalyzed Domino Reaction of 3‑Cyclopropylideneprop-2-en-1-ones

CuCl-catalyzed cyclization–dimerization reactions of 3-cyclopropylideneprop-2-en-1-ones provide an interesting route to benzofuran-7­(3aH)-one derivatives with one highly strained three-membered ring and one four-membered ring via intramolecular cycloisomerization, sequential bimolecular [4 + 2] cycloaddition, opening of the oxa-bridge, and ring contraction. Furthermore, the reaction was monitored by NMR experiments to unveil some key intermediates.