Hydrochloric Acid → 3-(difluoromethyl)-5-fluoro-1-methyl-1H-pyrazole-4-carboxylic acid

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Reaction Steps

67.5 g of a solution (10% molar) of 3-(difluoromethyl)-5-fluoro-1-methyl-1H-pyrazole-4-carbonyl fluoride in tetrahydrothiophene-1,1-dioxide were added dropwise to 400 mL of an aqueous 1N NaOH solution. During the addition, the temperature was kept below 20° C. After 2 h of stirring at room temperature, the mixture was carefully acidified to pH 2 using concentrated hydrochloric acid. The white precipitate formed was filtered off, washed with water and dried. This gave 6 g of 5-fluoro-3-(difluoromethyl)-1-methyl-1H-pyrazole-4-carboxylic acid as a white solid.

Provenance & Evidence