Dual Roles of Co₂(CO)₈ Enable Carbonylative Ring Expansion of Thietane under Ambient CO Pressure

Cobalt-catalyzed carbonylative ring expansion of thietane under ambient CO pressure was developed, affording a variety of thioacetones in moderate to high yields. dual roles of Co₂(CO)₈ as the precursor of both carbonylation catalyst and Lewis acid was revealed by control experiments and spectroscopic characterization. The carbonylative ring expansion under CO gas-free conditions was demonstrated by using Co₂(CO)₈ as both CO surrogate and pre-catalyst.