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.