Hydrochloric Acid → 2-(2,4-dichlorophenyl)-6-methyl-1,2,4-triazine-3,5(2H,4H)-dione

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Reaction Steps

To a stirred solution of 4.32 g (0.020 mole) of 2,4-dichlorophenylhydrazine hydrochloride in 100 mL of water and 50 mL of ethanol was added dropwise 2.14 g (0.024 mole) of pyruvic acid in 50 mL of water. Upon complete addition, a precipitate formed and was collected by filtration and dried under reduced pressure at ambient temperature. The solid hydrazone product was dissolved in 100 mL of toluene to which 4.8 g (0.041 mole) of thionyl chloride was added. The resultant mixture was stirred and heated at reflux for 0.5 hour. Distillation of the solvent under reduced pressure left a solid residue, which was dissolved in 100 mL of toluene. Urethane (2.2 g, 0.024 mole) was added, and the resultant solution heated at reflux with stirring for two hours. The solvent was removed from the mixture by distillation under reduced pressure to leave a residue. This residue was subjected to column chromatography on silica gel, eluting with ethyl acetate:heptane (1:1). Appropriate fractions were combined, and the solvent removed by evaporation to leave a gummy residue. The residue was dissolved in 75 mL of ethanol and 75 mL of 1N sodium hydroxide. The resultant solution was heated to 60° C., then poured into a mixture of 3N hydrochloric acid and ice. A solid formed which was collected by filtration and dried under reduced pressure. Recrystallization from tetrahydrofuran:heptane provided 2.0 g of 2-(2,4-dichlorophenyl)-6-methyl-1,2,4-triazine-3,5(2H,4H)-dione (mp 197° C. dec), Compound 4 in the tables.

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