FREMGANGSMAADE TIL FREMSTILLING AF 4-METHYL-5-OXO-3-THIOXOTETRAHYDRO-1,2,4-(2H,4H)-TRIAZINER

4-Methyl-5-oxo-3-thioxo-tetrahydro-1,2,4-(2H,4H)-triazines, which are intermediate products for known herbicides, can be prepared in high yields by a process in which an acyl cyanide of the general formula R-CO-CN (II) wherein R represents an optionally substituted aliphatic radical having up to 12 carbon atoms, an optionally substituted cycloalkyl radical having 3 to 10 carbon atoms, an optionally substituted phenyl or naphthyl radical or an optionally substituted heterocyclic radical, is reacted with a carboxylic acid anhydride of the general formula R1-CO-O-CO-R1 (II) in which R1 represents an optionally substituted aliphatic radical having up to 8 carbon atoms or an optionally substituted phenyl radical, in the presence of a strong acid and, if appropriate, in the presence of a solvent, at a temperature between -50 DEG and 150 DEG C., and the reaction mixture thus obtained is then reacted directly with 4-methyl-thiosemicarbazide (CH3-NH-CS-NH-NH2).