Carbamic acid, ethyl ester → 2-(2,4-dichlorophenyl)-1,2,4-triazine-3,5(2H,4H)-dione

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Reaction Steps

To a stirred mixture of 5.9 g (0.025 mole) of 2-oxoacetic acid 2,4-dichlorophenylhydrazone in 100 mL of toluene was added 6.0 g (0.051 mole) of thionyl chloride. The reaction mixture was heated at reflux for 10 minutes resulting in a clear solution. This solution was cooled and the solvent was removed by evaporation under reduced pressure leaving a solid residue. This solid was dissolved in 100 mL of fresh toluene to which 2.7 g (0.030 mole) of urethane was added. The resultant mixture was heated at reflux for three hours, removing about 50 mL of solvent by means of a Dean-Stark trap. The reaction mixture was cooled and the solvent removed by evaporation under reduced pressure leaving a yellow residue. This residue was dissolved in 50 mL of ethanol to which was added 50 mL of an aqueous 10% potassium hydroxide solution. The resultant mixture was heated on a steam bath for 15 minutes. The mixture was allowed to cool and was diluted with additional water. The dilute aqueous mixture was washed with diethyl ether. The aqueous phase was acidified with concentrated hydrochloric acid and the acidic mixture was extracted with ethyl acetate. The extract was dried over anhydrous magnesium and sulfate and filtered. The filtrate was evaporated under reduced pressure leaving a residue. This residue was dissolved in about 20 mL of ethyl acetate and filtered through a pad of silica gel. The filtrate was evaporated under reduced pressure leaving a solid. Purification of this solid by recrystallization from ethyl acetate/n-heptane yielded 3.0 g of 2-(2,4-dichlorophenyl)-1,2,4-triazine-3,5(2H,4H)-dione.

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