Methanol → 7-Difluoromethyl-5-(4-trifluoromethyl-phenyl)-pyrazolo[1,5-a]pyrimidine-3-carboxylic acid

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Reaction Conditions

Reaction Steps

A stirred mixture of commercially available 3-amino-4-ethoxycarbonyl-pyrazole (3.38 g, 22 mmol) and 4,4-difluoro-1-(4-trifluoromethyl-phenyl)-butane-1,3-dione (5.8 g, 22 mmol) in acetic acid (45 ml) was heated under reflux conditions for 1.5 h. The reaction mixture was evaporated and the crude product (yellow solid, 8.5 g, 22 mmol) was dissolved in a mixture of 2M KOH in methanol (176.5 ml, 0.35 mol) and water (85 ml). The reaction mixture was stirred at 60° C. for 1.5 h, poured into ice/water (200 ml), acidified with 3N sulfuric acid (pH=4) and stirred at room temperature for 30 min. The precipitate was collected by filtration and further purified by crystallization from diethylether/methanol to give the title compound (4.51 g, 57%) as an off-white solid. MS (ISP) 356.1 [(M−H)−]; m.p. 261° C.

Provenance & Evidence