Asymmetric Synthesis of Remote Quaternary Centers by Copper-Catalyzed Desymmetrization: An Enantioselective Total Synthesis of (+)-Mesembrine

Catalytic asymmetric syntheses of remote quaternary stereocenters have been developed by copper-catalyzed 1,4-hydrosilylation of gamma,gamma-disubstituted cyclohexadienones. A variety of cyclohexenones have been synthesized in good yield and excellent enantioselectivity. Versatile 2-silyloxy diene intermediates bearing gamma,gamma-disubstituted all carbon stereogenic centers can be isolated from the mild reaction conditions. The utility of this strategy is exemplified in a catalytic asymmetric total synthesis of (+)-mesembrine.