Phosphorus oxychloride → 6-Chloro-1,3-dimethyl-2,4(1H,3H)-pyrimidinedione

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Reaction Steps

To 110 g of the resulting 1,3-dimethylbarbituric acid was added 32 ml of water, and 800 ml of phosphorus oxychloride was slowly added dropwise thereto. After heating at reflux for 1.5 hours, the phosphorus oxychloride was removed by distillation at normal pressure. The residue, while hot, was poured onto ice, and the thus formed crystals were collected by filtration. The filtrate was extracted three times with chloroform and dried over anhydrous sodium sulfate, followed by distillation to remove chloroform. The residue was combined with the above obtained crystals. Recrystallization from water gave 80 g (64%) of 6-chloro-1,3-dimethyluracil having a melting point of 113° to 115° C.

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