Copper-Catalyzed Enantioselective Conjugate Borylation of Silacyclohexadienones to Construct Highly Congested Stereocenters Adjacent to C−Si Bonds

Chiral organosilicon compounds featuring a silicon-stereogenic center have attracted renewed interest in recent years. However, the enantioselective synthesis of such molecules containing both carbon and silicon stereocenters from prochiral precursors remains a significant challenge. Herein, we report a desymmetrization strategy that enables the simultaneous construction of two adjacent stereocenters at silicon and carbon. This transformation is achieved through the enantioselective copper-catalyzed 1,4-addition of boron nucleophiles to silacyclohexadienones. A subsequent conjugate borylation of the remaining acceptor establishes a third contiguous stereocenter at carbon. Both steps proceed with high stereocontrol, and the resulting α,α′-bisborylated silicon-stereogenic silanes allow orthogonal functionalization of the two boryl groups. This methodology thus provides access to three stereogenic centers within a highly congested framework. Computational studies provide insight into the group- and facial-selectivity governing the initial desymmetrization, supporting the experimentally determined enantio- and diastereoselectivity-determining step.