Phosphorus oxychloride → 5-Chloro-1-methyl-3-phenyl-1H-pyrazole

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Reaction Steps

To a solution of phosphorous oxychloride (2,015 g, 19 moles) is added solid 1-methyl-3-phenylpyrazolin-5-one (2,073 g, 11.9 moles) with stirring and warming. At 100°C. the mixture becomes homogeneous. The reflux temperature rises from 119°C. to 143°C. over a period of 30 hours. After cooling the mixture is poured into ice and water (8 l) with stirring. After 4 hours the slurry is filtered and the filter cake added to 4 l of water containing 1.5 l of 10% sodium hydroxide solution with stirring. Removal of the solid by filtration followed by a recrystallization from hexane yields 1,523 g of product, having a melting point ranging from 61°C. to 62°C.

Provenance & Evidence