Anti-Markovnikov ring-opening of sulfonium salts with alkynes by visible light/copper catalysis

Internal alkynes are widespread skeletons in bioactive molecules and materials which are also used as important building blocks in chemical synthesis. Herein, we report a novel and efficient copper-catalyzed Sonogashira reaction between sulfonium salts and alkynes through an anti-Markovnikov ring-opening pathway promoted by visible light. The coexistence of the nitrogen and phosphorus ligands in the system is the key to the success of this reaction. This radical type ring-opening reaction affords a new strategy for the synthesis of internal alkynes. Furthermore, this study is also an effective complement to the diverse reaction patterns of sulfonium salts.