Synthesis and properties of 5‐aroylamino‐2H‐1,2,4‐thiadiazol‐3‐ones

Abstract 5‐Aroylamino‐2H‐1,2,4‐thiadiazol‐3‐ones 3 were obtained from the corresponding 1‐aroyl‐2‐thiobiurets 2 by oxidative cyclization with bromine. 5‐Aroylamino‐2H‐1,2,4‐thiadiazol‐3‐ones 3 can exist in two tautomeric forms a lactam form and a lactim form. On the basis of the 13C nmr spectra and additional experimental information, it has been established that the stable form, in which these compounds exist, is the lactam form.