Sodium Hydroxide → N-tert-Butyl-3,5-di(difluoromethyl)-4-pyrazolecarboxylic acid

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Reaction Steps

N-tert-Butyl-3,5-di(difluoromethyl)-4-pyrazolecarboxylic acid ethyl ester (3.40 g, 11.5 mmol) in ethanol (23 ml) was admixed gradually with an 8N aqueous sodium hydroxide solution (4.3 ml) and stirred at room temperature for 3 h. The solvent was removed by rotary evaporation; the residue was taken up in water (40 ml) and extracted with diethyl ether (20 ml). Acidification to pH 1 with 6M HCl was followed by extraction with ethyl acetate (3×30 ml). The combined organic phases were dried over sodium sulphate and filtered, and the solvent was removed by rotary evaporation. N-tert-Butyl-3,5-di(difluoromethyl)-4-pyrazolecarboxylic acid (3.0 g, 11.2 mmol, 97%) was isolated as a pale reddish solid.

Provenance & Evidence