A Stepwise, Nitrosonium-Catalyzed Aerobic Oxidation of Thiols to Disulfides and Thiosulfonates

A selective and controllable oxidation of thiols to disulfides or thiosulfonates has been developed using molecular oxygen, trifluoroacetic acid, and catalytic NaNO3. Both aromatic and aliphatic thiols afford high yields. Sequential oxidation from thiols to disulfides and then to thiosulfonates was observed, with the second step governed by the acid concentration and substrate steric and electronic effects. Acid and oxygen cooperatively enable in situ generation and turnover of the active nitrosonium species.