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 γ-butenolide or
γ-lactone connected to a cycloalkane or cycoalkene moiety.