Rhodium-catalyzed carbonylation of spiropentanes

Spiropentanes undergo carbonylation under an atmosphere of carbon monoxide in the presence of a rhodium(I)-phosphine catalyst, giving 3-methylcyclopent-2-enones. The catalytic cycle involves two mechanistically different carbon-carbon cleavage processes. The spiropentane carbonylation was successfully applied to a short synthesis of (+/-)-beta-cuparenone.