[CH3:1][C:2]1[CH2:3][N:4]([NH:9]C(=O)C)[C:5](=[O:8])[NH:6][N:7]=1.Cl.Cl.[NH2:15][N:16]1[CH2:21][C:20](C)=[N:19]NC1=O.[CH3:24][OH:25]>>[NH2:9][N:4]1[CH2:3][C:2]([CH3:1])=[N:7][NH:6][C:5]1=[O:8].[NH2:15][C:16]1[C:24](=[O:25])[NH:4][N:19]=[N:20][CH:21]=1A suspension is prepared of 39.9 g (0.234 mol) 6-methyl-4-acetylamino-4,5-dihydro-1,2,4-triazin-3-(2H)-one in 99 g 95% methanol. The suspension is heated to 45° C. and becomes a clear colourless solution. At between 45° and 50° C. a total of 15.4 g (0.421 mol) HCl are bubbled through this solution over a 2 to 3 hour period. After about 30% of the HCl has been added the reaction mixture is seeded with 4-amino-6-methyl-3-oxo-2,3,4,5-tetrahydro-1,2,4-triazine hydrochloride. Thereafter 4-amino-6-methyl-3-oxo-2,3,4,5-tetrahydro-1,2,4,-triazine precipitates out continuously as the hydrochloride salt. After about 2 hours stirring, the maximum conversion of over 99% is reached. The reaction mixture is brought to pH 5 by the addition of 50% NaOH solution. The free aminotriazinone 4-amino-6-methyl-3-oxo-2,3,4,5-tetrahydro-1,2,4-triazine is formed in an amount of 29.7 g representing 14.3% by weight of the solution. This represents a yield of 99.2% of theory.
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