Lactone Formation by Rhodium-Catalyzed C−C Bond Cleavage of Cyclobutanone

As a coordinating ligand, the phenol group in appropriately substituted cyclobutanones facilitates the RhI-catalyzed activation of the C−C bond between the carbonyl group and the α-carbon atom. This novel reaction leads, depending on the position of the phenol group on the cyclobutanone ring, to lactones of varying ring size (for example, as shown for a seven-membered-ring lactone).