Hydrotrifluoromethylthiolation of Unactivated Alkenes and Alkynes with Trifluoromethanesulfonic Anhydride through Deoxygenative Reduction and Photoredox Radical Processes.

An ongoing challenge in trifluoromethylthiolation reactions is the use of less expensive and easily available trifluoromethylthio sources. Herein, we disclose an unprecedented usage of trifluoromethanesulfonic anhydride (Tf2O) as a radical trifluoromethylthiolating reagent. Hydrotrifluoromethylthiolation of unactivated alkenes and alkynes with Tf2O in the presence of PMePh2 and H2O under visible-light photo-redox catalysis gave the addition products. The trifluoromethylthio radical (CSCF3) was first formed from Tf2O through a photoredox radical processes and deoxygenative reduction of PMePh2, and H2O serves as the H-atom donor for the hydrotrifluoromethylthiolation reaction. This reaction provides a new strategy for radical trifluoromethylthiolation.