| 摘要 |
In the process for the preparation of allopurinol by direct cyclisation of 5-aminopyrazole-4-carboxylate with formamide at elevated temperature, the cyclisation is carried out in the presence of ammonia, in particular ammonia which is introduced continuously into the reaction mixture. The liquid reaction medium used is, in particular, the formamide itself. The process improves the economy of commercial allopurinol production.
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