Ethyl 2-(ethoxymethylene)-4,4,4-trifluoroacetoacetate → ethyl 1-(4-cyanophenyl)-5-(trifluoromethyl)-1H-pyrazole-4-carboxylate

A solution of (Z)-ethyl 2-(ethoxymethylene)-4,4,4-trifluoro-3-oxobutanoate (2.41 g, 10.03 mmol) in ethanol (10 mL) was added dropwise to a stirred solution of 4-hydrazinylbenzonitrile hydrochloride (1.702 g, 10.03 mmol), in ethanol (50 mL) cooled to −10° C. The resulting solution was allowed to stir at room temperature for 16 hours. The reaction mixture was evaporated to dryness and the residue redissolved in EtOAc (100 mL), and washed sequentially with water (50 mL) and saturated brine (50 mL). The organic layer was dried over MgSO4, filtered and evaporated to afford crude product. The crude product was purified by flash silica (120 g) chromatography, elution gradient 10 to 60% EtOAc in isohexane. Pure fractions were evaporated to dryness to afford ethyl 1-(4-cyanophenyl)-5-(trifluoromethyl)-1H-pyrazole-4-carboxylate (2.400 g, 77%) as a white solid.