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

摘要

1. Process for the preparation of 4-amino-6-tert.-butyl-3-methylthio-1,2,4-triazin-5(4H)-one of the formula see diagramm : EP0033476,P6,F1 characterised in that (1) pivaloyl cyanide of the formula (CH3 )3 C-CO-CN is first reacted with an anhydrous hydrogen halide in the presence of a carboxylic acid with 1-6 C-atoms which is liquid under the reaction conditions, as the solvent, in a pressure range of 1-10 bars, and if appropriate then with water, in each case at temperatures between -50 and +50 degrees C, (2) the trimethylpyruvic acid amide of the formula (CH3 )3 C-CO-CO-NH2 which is thereby formed is reacted, either directly in the solution obtained or after intermediate isolation, and if appropriate after prior saponification to give free trimethylpyruvic acid, with thiocarbohydrazide (H2 N-NH-CS-NH-NH2 ) in an aqueous solution containing a hydrogen halide acide, at temperatures from 20 to 100 degrees C, in a manner which is in itself known to give 4-amino-6-tert.-butyl-3-mercapto-1,2,4-triazin-5(4H)-one (IV) and (3) this intermediate product (IV) is methylated in alkaline solution in the customary manner by means of methyl iodide or methyl bromide.