[CH3:1][C:2]1[C:3](=[O:9])[NH:4][C:5](=[S:8])[NH:6][N:7]=1.[OH-].[Na+].[CH3:12]I>C(O)C>[CH3:1][C:2]1[C:3](=[O:9])[NH:4][C:5]([S:8][CH3:12])=[N:6][N:7]=1To a solution of 6-methyl-3-thioxo-3,4-dihydro-1,2,4-triazin-5(2H)-one (4, 5.80 g, 40.6 mmol) in absolute ethanol (250 mL) was added NaOH (1.96 g, 49.1 mmol) followed by MeI (11.5 g, 81.2 mmol). The mixture was heated at 40° C. for 15 h. Most of the solvent was evaporated under reduced pressure. Water was added to the residue. The precipitated white solid was collected by filtration and washed with ethanol to give 5 (3.06 g). The aqueous phase was extracted with CH2Cl2 (80 mL×4). The combined extracts were dried over Na2SO4 and concentrated to give 3.34 g crude product. This was purified by column chromatography on silica gel, and eluted with 1:1 to 1:2 petroleum ether-ethyl acetate to provide 6-methyl-3-(methylthio)-1,2,4-triazin-5(4H)-one (5). MS: m/z, 158 (100%, M+1).
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