Computational Understanding of Dual Gold and Photoredox-Catalyzed Regioselective Thiosulfonylation of Alkenes.

Herein, a computational work was carried out to gain mechanistic insights into dual gold and photoredox-catalyzed regioselective thiosulfonylation of alkenes with PhSO 2 SCF 3 . Computational results suggest that it is more favorable for the complex of Au(I) with PhSO 2 SCF 3 ( INT1 ), instead of an Au(I) catalyst or individual substrates, to quench the excited *[Ru] II photocatalyst in a single-electron oxidative manner to afford [Ru] III . The complexation of the Au(I) catalyst with PhSO 2 SCF 3 could lead to a substantially lowered energy level of the lowest unoccupied molecular orbital, which may be mainly responsible for the feasibility of INT1 in quenching the excited photocatalyst. The resultant single-electron reduced complex, subsequently, is ready to undergo a S-S bond cleavage to form an Au(I)-SCF 3 species and a benzenesulfonyl radical. Next, the yielded Au(I)-SCF 3 species could undergo single-electron oxidation by [Ru] III to afford an Au(II) intermediate. Subsequently, the binding with an alkyl radical for the formed Au(II) species could occur to further convert to an Au(III) species, from which the final product can be furnished by a reductive elimination step and the Au(I) catalyst is regenerated. Thus, an Au(I)/Au(II)/Au(III)/Au(I) catalytic cycle is suggested to mainly account for the regioselective thiosulfonylation of alkenes.