Visible-light-induced chemo-, diastereo- and enantioselective α-C(sp)-H functionalization of alkyl silanes.

A catalytic asymmetric α-C(sp)-H functionalization of alkyl silanes with benzosultams was realized by merging photoredox and chiral Lewis acid catalysis. The key to success was the choice of photocatalyst with an appropriate redox potential and non-nucleophilic solvent, providing a novel entry to chiral organosilanes containing two adjacent tri- and tetra-substituted stereocenters with high to efficient diastereo- and enantioselectivity (up to 99% ee, 94 : 6 dr) under mild reaction conditions. Based on the control experiment and spectral analysis, an initial single electron transfer reduction of a benzosultam-triggered simultaneous or stepwise electron transfer/proton transfer process was proposed to rationalize the favored C(sp)-H functionalization rather than desilylation.