Rh-Catalyzed Carbonyl Hydroacylation:  An Enantioselective Approach to Lactones

This communication describes the design and execution of a novel approach to forming chiral lactones via C−H bond activation. The strategy features an unprecedented enantioselective Rh-catalyzed hydroacylation of carbon−oxygen double bonds. Representative keto-aldehydes (derived from salicylaldehyde) undergo cyclization with complete regioselectivity to afford seven-membered lactones in great enantiomeric excess (≥99% ee). The basicity of the phosphine ligand is shown to play a critical role in promoting hydroacylation over competitive decarbonylation.