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.

Automated summary

The aerobic visible-light induced intermolecular S-N bond construction without the addition of photosensitizer, metal, or base allows for the synthesis of 1,2,4-thiadiazoles from thioamides. The preliminary mechanistic investigation indicates that the excited state of thioamides undergoes a single-electron-transfer process to form thioamidyl radicals, which can be further converted into 1,2,4-thiadiazoles through desulfurization and oxidative cyclization. This reaction with good functional group tolerance represents a green method for the construction of S-N bonds.