Visible Light‐Mediated, Iodine‐Catalyzed Radical Cascade Sulfonylation/Cyclization for the Synthesis of Sulfone‐Containing Coumarin under Photocatalyst‐Free Conditions

We have presented a visible‐light mediated, iodine catalyzed radical cascade sulfonylation/cyclization reaction by employing iodine as catalyst without addition of any of photocatalyst and oxidant. A number of sulfone‐containing coumarin derivatives with different substituent and functional groups were obtained in moderate to good yields. Besides, the practicality and utility of this protocol were demonstrated by the scale up synthesis. Furthermore, mechanistic investigations including control experiments and light on/off studies indicated that visible‐light irradiation and iodine catalyst were the essential elements to fulfill the radical cascade sulfonylation/cyclization process. This protocol featured green, economical and efficient, and opens a new opportunity for accessing to structurally diverse sulfone‐containing coumarin derivatives. Visible light‐mediated radical cascade sulfonylation/cyclization reaction by employing iodine as catalyst without addition of any of photocatalyst and oxidant has been reported. Under the optimal reaction conditions, a series of sulfone‐containing coumarin derivatives were obtained in moderate to good yields. Further, mechanistic investigations indicated that the reaction was started by visible light irradiation through iodine‐catalyzed free radical cascade sulfonylation/cyclization pathway.