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.