Synthesis of Heterocyclic Sulfonium Triflates by Cu-Catalyzed Selective Sarylation with Aryl(mesityl)iodonium Salts

An efficient method for synthesizing cyclic arylsulfonium salts has been developed by selective aryl transfer to the sulfur atom from aryl(mesityl)iodonium triflates, a recyclable series of diaryliodonium salts. The utilization of sulfonium salts as valuable intermediates is well-established, as they exhibit high reactivity under conditions of heating or UV irradiation. However, their synthesis typically involves the reaction of diarysulfoxide with acid anhydride, which requires the oxidation of sulfur(II) to sulfoxide(IV) and thus limits the scope of synthesis. Hence, in this study, we employed recyclable mesityliodonium(III) salts and copper catalysis. The method was used to synthesize cyclic arylsulfonium salts without the need for preoxidation of the sulfur atom, resulting in a facile and high-yield synthesis. The desired cyclic arylsulfonium salts were synthesized through selective transfer of the aryl group from mesityliodonium salts, demonstrating the effectiveness of the new approach.