Enantioselective Insertion of Vinyl Diazoacetates into O-H Bonds of Carboxylic Acids

A highly regio- and enantioselective insertion of vinyl diazoacetates into O-H bonds of carboxylic acids has been realized by cooperative catalysis of an achiral rhodium complex and a chiral phosphoric acid. The insertion reaction exhibits highly carbenic reactivity rather than vinylogous reactivity, representing a rare example towards alpha-acyloxyl-beta,gamma-unsaturated esters, and the corresponding esters were obtained in good yields with good enantioselectivities (up to 97% ee). A rhodium and phosphoric acid-catalyzed regio- and enantioselective vinyl carbene insertion into the O-H bonds of carboxylic acids has been achieved.