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 (±)-β-cuparenone.