Isothiocyanates. I. Addition of Urea to Aroyl Isothiocyanates and Conversion of the Monoadducts into Monothiobiuret, 4-Thioxo-1,3,5-triazin-2-ones and 1,2,4-Thiadiazol-3-ones

The hitherto unknown 1-aroyl-2-thiobiurets were synthesized by addition of urea to aroyl isothiocyanates. Treatment of 1-benzoyl-2-thiobiuret with concentrated hydrochloric acid effected hydrolysis to monothiobiuret. On the other hand, treatment of 1-aroyl-2-thiobiurets with alkali gave 6-aryl-4-thioxo-1,2,3,4(or 2,3,4,5)-tetrahydro-1,3,5-triazin-2-ones. Oxidation of the 1-aroyl-2-thiobiurets with hydrogen peroxide in the presence of hydrochloric acid gave 5-aroylamino-2.3-dihydro-1,2,4-thiadiazol-3-ones.