Visible-light-induced intramolecular C-S bond formation for practical synthesis of 2,5-disubstituted 1,3,4-thiadiazoles

A general and facile visible-light mediated protocol for the synthesis of 2-arylamino-5-aryl-1,3,4- thiadiazoles via one-pot condensation and intramolecular C-S coupling cascade reaction has been developed. This protocol is mild, practical, metal-free and exogenous oxidant-free, and only involves Eosin Y as photocatalyst using oxygen as the sole terminal oxidant. This protocol exhibits synthetic simplicity, broad scope of substrates, and excellent functional group compatibility. Gram-scale synthesis can be also facilitated with a satisfactory yield, which opens up the possibility of practical applications.