Visible-Light-Induced Photocatalyst-Free Radical Trifluoromethylation

An attractive, versatile, and operationally simple, visible-light-induced, transition-metal-free, photocatalyst-free, and oxidant-free trifluoromethylation has been demonstrated. Triflic anhydride (Tf 2 O), being inexpensive and readily available, was chosen as the radical trifluoromethyl source. Thianthrene was used as a recyclable Tf 2 O-activating reagent, and a high-yielding and scalable trifluoromethylation reaction was achieved. Density functional theory and mechanistic studies showed that a free radical homolytic process excited by visible light is involved in this reaction, generating a key trifluoromethyl radical intermediate.