Synthesis of S‐Arylthioxanthonium Trifluoromethanesulfonates From Thioxanthones and Diaryliodonium Salts by Copper(II) Catalysis and Application to Aryl–Heteroaryl Bond Formation by Direct LED Irradiation

A short and versatile route to S‐arylthioxanthonium trifluoromethanesulfonates via a Cu‐catalyzed reaction of diaryliodonium trifluoromethanesulfonates and commercially available thioxanthones is described. Variously substituted S‐arylthioxanthonium salts were prepared in only one step from diaryliodonium salts in moderate to good yields. Then, we show one of the first applications of an S‐arylthioxanthonium trifluoromethanesulfonate, as an efficient aryl radical precursor by simple and mild direct 365‐nm LED irradiation. In preliminary experiments, this aryl radical was successfully trapped with furan without any metallic photocatalyst, thereby enabling the first formation of a new aryl–heteroaryl bond from a sulfonium salt derived from thioxanthone.