Tosylation of 2‐(monosubstituted)amino‐1,3,4‐thiadiazoles

Tosylation of 2‐benzylamino‐ and 2‐anilino‐5‐phenyl‐1,3,4‐thiadiazoles (1a,b) in the presence of triethylamine affords the ring‐sulfonylated products 2a,b which isomerize in a later stage of the reaction to the exocyclic amino‐sulfonylated products 3a,b. Acetylation of 1a,b gives the acylamino substituted thiadiazoles 4a,b directly as the only reaction products. The 13C nmr data are discussed and their importance for the study of prototropic tautomerism and for structure elucidation of the reaction products is indicated.