Catalytic Enantioselective Vinylogous Mukaiyama-Michael Addition of 2-Silyloxyfurans to Cyclic Unsaturated Oxo Esters

The copper-catalyzed asymmetric addition of 2-silyloxyfurans to cyclic unsaturated oxo esters is reported. The reaction proceeds with excellent diastereocontrol (usually dr 99:1) and modest to high enantioselectivity, depending on the nature of the ester group and the substitution of the cyclic oxo ester. We have shown that these substrates can be transformed into a variety of building blocks bearing a gamma-butenolide or gamma-lactone connected to a cycloalkane or cycoalkene moiety.