cobalt‐diphosphine catalyst has been found to efficiently promote intramolecular cyclization of ortho‐cyclopropylvinyl‐ and cyclopropylidenemethyl‐substituted benzaldehydes into benzocyclooctadienone and benzocycloheptadienone derivatives, respectively. This ring‐opening hydroacylation likely involves aldehyde C−H oxidative addition, olefin insertion, cyclopropane cleavage by β‐carbon elimination, and