Diastereo- and Enantioselective Catalytic Radical Oxysulfonylation of Alkenes in β,γ-Unsaturated Ketoximes

The asymmetric radical-initiated difunctionalization of internal alkenes, which creates two vicinal stereocenters, has been a significant synthetic challenge despite the tremendous progress achieved for terminal alkenes. This is attributable to the common stepwise mechanism that involves an initial free radical addition to the alkene in a nonstereoselective fashion. We report here the first asymmetric radical 1,2-oxysulfonylation of both terminal and internal aryl alkenes in β,γ-unsaturated ketoximes in the presence of copper(I)-cinchona alkaloid-based sulfonamide catalyst. The experimental and computational mechanistic studies collectively support a CuII-CuI mechanism featuring fast, reversible addition of sulfonyl radicals to alkenes and subsequent rate- and stereo-determining C–O bond formation, namely, a scenario under Curtin-Hammett kinetic control. The method provides a robust platform for collective synthesis of a diverse array of valuable chiral sulfonyl-containing building blocks.