Hydrazine hydrate (1:1) → 5-phenethyl-1H-pyrazole-3-carboxylic acid ethyl ester

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Reaction Steps

Hydrazine hydrate (0.109 mL, 2.24 mmol) was added to a stirring room temperature solution of 19 (0.5570 g, 2.24 mmol) in EtOH (2.2 mL, 1 M) under N2. The reaction was then heated to reflux until judged complete by HPLC. The reaction was concentrated and purified by silica gel chromatography (Combiflash column, 70:30:2 Hexanes:CH2Cl2:2N NH3 in EtOH). Only pure fractions were combined and concentrated to obtain 0.2983 g (54.4%) of 20. 1H (CDCl3, 400 MHz): δ 11.7 (1H, broad s), 7.30-7.11 (5H, m), 6.60 (1H, s), 4.32 (2H, q, J=7.1 Hz), 3.07-2.92 (4H, m), 1.31 (3H, t, J=7.1 Hz) ppm. Partial 13C (CDCl3, 100 MHz): δ 162.13, 147.42, 140.97, 128.72, 128.59, 126.48, 106.79, 61.16, 35.63, 28.18, 14.47 ppm. DEPT (CDCl3, 100 MHz): CH3 carbons: 14.47; CH2 carbons: 61.16, 35.63, 28.18; CH carbons: 128.72, 128.59, 126.48, 106.79 ppm. HPLC: 9.299 min.

Provenance & Evidence