Method for the preparation of 4-amino-6-tert. butyl-3-methylthio-1,2,4-triazin-5(4H)-one

摘要

In the preparation of 4-amino-6-tert.-butyl-3-methylthio-1,2,4-triazin-5-(4H)-one of the formula IMAGE wherein pivaloyl cyanide of the formula (CH3)3C-CO-CN is reacted to form an intermediate, the intermediate is condensed with thiocarbohydrazide of the formula NH2-NH-CS-NH-NH2 to form 4-amino-6-tert.-butyl-3-mercapto-1,2,4-triazin-5-(4H)-one of the formula IMAGE and the 4-amino-6-tert.-butyl-3-mercapto-1,2,4-triazin-5-(4H)-one is alkylated to replace the H atom on the sulphur by -C1-4-alkyl, the improvement which comprises reacting the pivaloyl cyanide with a carboxylic acid anhydride of the formula R-CO-O-CO-R in which R is an optionally substituted aliphatic radical with up to 8 carbon atoms or an optionally substituted phenyl radical, in the presence of a strong acid at a temperature between about -50 DEG and +150 DEG C., and then directly reacting the reaction mixture thus obtained with the thiocarbahydrazide. Advantageously R is CH3, the strong acid is concentrated sulphuric acid, the pivaloyl cyanide is effected at a temperature between about 0 DEG and 100 DEG C., the condensation with thiocarbohydrazide is effected, in the presence of a mineral acid, in an aqueous or aqueous-alcoholic medium, and the alkylation is effected using methyl iodide or methyl bromide in the presence of sodium hydroxide at about 0 DEG to 50 DEG C.