CC Bond Activation by Octacarbonyldicobalt: [3+1] Cocyclizations of Methylenecyclopropanes with Carbon Monoxide

Activation of CC bonds in cyclopropanes with a cobalt complex: Methylenecyclopropanes react with one equivalent of [Co2(CO)8] under mild conditions to give 2-methylenecyclobutanones in moderate to good yields (up to 85 %). The reaction also proceeds with a catalytic amount of the cobalt complex under an atmosphere of CO (balloon) to give products in good yields (up to 90 %; see scheme).