Preparation of 4,6-di:chloro-pyrimidine from di:hydroxy-pyrimidine

摘要

Preparation of 4,6-dichloropyrimidine comprises (a) chlorination of 4,6-dihydroxypyrimidine (I) with phosphorus oxychloride in the absence of base; (b) treatment of the obtained reaction mixture (A) with chlorine in the presence of phosphorus trichloride, so that the PCl3 is always in excess; and (c) distillation of the treated reaction mixture (B). In step (b), a maximum of 99.9wt.% of the available chlorophosphoric acids is reacted, and the rest of the chlorophosphoric acids are removed in the distillation of step (c) before isolation of 4,6-dichloropyrimidine.