Addition of arylureas to aroyl isothiocyanates and the synthesis of 1‐aroyl‐5‐aryl‐2‐thiobiurets and 2‐aryl‐5‐aroylamino‐2,3‐dihydro‐1,2,4‐thiadiazol‐3‐ones

The hitherto unknown 1‐aroyl‐5‐aryl‐2‐thiobiurets ( 5a – h ) were synthesized by addition of mono arylureas ( 4 ) to aroyl isothiocyanates ( 3 ). Treatment of 1‐aroyl‐5‐aryl‐2‐thiobiurets ( 5a – h ) with alkali gave 5‐aryl‐2‐thiobiurets ( 6a – e ). Oxidation of 1‐aroyl‐5‐aryl‐2‐thiobiurets ( 5d , f , h ) with hydrogen peroxide in the presence of hydrochloric acid or bromine in chloroform gave 2‐aryl‐5‐aroylamino‐2,3‐dihydro‐1,2,4‐thiadiazol‐3‐ones ( 7a – c ).