Rapid construction of a polysubstituted “caged” oxa-bishomocubane framework from vinylidenecyclopropanes through a sequential dual catalysis of copper(i) and visible-light-induced photosensitization

This study describes a sequential dual catalytic transformation involving copper(I)-catalyzed cyclization/isomerization/migration–dimerization and visible-light photo-induced intramolecular [2 + 2] cycloaddition of vinylidenecyclopropanes for the rapid construction of polysubstituted “caged” oxa-bishomocubane products. The reaction proceeds through an in situ generated cyclobutane-fused furan upon Cu(I) catalysis and its dimerization occurring via an intermolecular [4 + 2] cycloaddition event. These dimerized dihydrofuran derivatives could undergo an intramolecular [2 + 2] cycloaddition upon visible-light irradiation, affording polysubstituted “caged” oxa-bishomocubane derivatives in moderate to good yields. This newly developed synthetic protocol features a simple operation with readily available starting materials in good step-economy in the facile synthesis of a “caged” product. The plausible cascade catalytic reaction mechanism has been also proposed on the basis of control experiments and density functional theory (DFT) calculation.