Propionitrile → 3-ethyl-1-(4-fluorophenyl)-5-methyl-1H-pyrazole-4-carboxylic acid tert-butylester

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According to AVV A, (Z)-3-(4-fluorophenylamino)-but-2-enoic acid tert-butylester (251.3 mg, 1.0 mmol, 1.0 equiv.) was stirred with Cu(OAc)2 (544.9 mg, 3.0 mmol, 3.0 equiv.) into propionitrile (3.0 ml, 41.9 mmol, 41.9 equiv.) for 24 hours at 120° C. The dark-brown/blue raw product (295.9 mg) was analyzed by means of 1H and 19F-NMR-spectroscopy. The 19F-NMR spectra showed the desired product (δ=−112.7 ppm) and N-(4-fluorophenyl)-acetamide (δ=−118.0 ppm) in a ratio of 89:11. After purification by means of column chromatography (silica gel (50 g), pentane/EtOAc 98:2→70:30→0:100), the product was obtained in the form of a yellowish oil (222.9 mg, 0.73 mmol, 73%).

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