Nickel-Mediated Ring Expansion Reactions of Benzocyclobutenones for Selective Construction of 5,7-Dihydro-6H-dibenzo[a,c][7]annulen-6-ones and 1H-Isochromen-1-ones.

Herein, we report the development of a general ring expansion strategy that involves the formal self-dimerization of benzocyclobutenones (BCBs) through nickel catalysis. These formal self-dimerizations of BCBs are efficient and scalable and provide a facile and unique construction of diverse seven-membered ring ketones and 1H-isochromen-1-ones with high structural diversity. Moreover, the solvent effects and CO atmosphere play a crucial role in promoting CO exclusion, which may address regioselectivity control toward the (4 + 4 - 1) product, while NaOAc as an additive under a N2 atmosphere promoted (4 + 2) product formation.