Aerobic Visible-Light Induced Intermolecular S−N Bond Construction: Synthesis of 1,2,4-Thiadiazoles from Thioamides under Photosensitizer-Free Conditions

Aerobic visible-light induced intermolecular S−N bond construction has been achieved without the addition of photosensitizer, metal, or base. With this strategy, 1,2,4-thiadiazoles can be obtained from thioamides. Preliminary mechanistic investigation suggested that the excited state of thioamides undergoes a single-electron-transfer (SET) process to afford thioamidyl radicals, which can be further transformed into a 1,2,4-thiadiazole through desulfurization and oxidative cyclization. The reaction has good functional group tolerance and represents a green method for the construction of S−N bonds.