Radical-Radical Cross-Coupling for C-S Bond Formation.

A new method was demonstrated to overcome the selectivity issue of radical-radical cross-coupling toward the synthesis of asymmetric diaryl thioethers. The preliminary mechanism was revealed by radical-trapping experiments, DFT calculations, and kinetics, etc., indicating that the C-S bond formed through cross-coupling of a thiyl radical and an aryl radical cation. Moreover, the formation of an aryl radical cation instead of the C-H bond cleavage was determined as the rate-limiting step.