Hydrazine hydrate (1:1) → Methyl 4-(1H-pyrazol-5-yl)benzoate

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To a solution of crude (E)-methyl 4-(3-(dimethylamino)acryloyl)benzoate (28.1 mmol) in EtOH (100 mL) was added hydrazine monohydrate (1.50 mL, 30.9 mmol) and the reaction was heated at 50° C. for 24 hours. The reaction temperature was then increased to 60° C. for 24 hours. Additional hydrazine monohydrate (1.5 mL) was added, and the reaction was heated at 60° C. for an additional 6 hours. The reaction was cooled, concentrated, and dried in a vacuum oven at 45° C. overnight to yield methyl 4-(1H-pyrazol-3-yl)benzoate as an orange solid (8.15 g, quantitative): mp 106° C. (dec); 1H NMR (400 MHz, CDCl3) δ 8.15-8.05 (m, 2H), 7.91-7.83 (m, 2H), 7.65 (d, J=2.4 Hz, 1H), 6.71 (d, J=2.3 Hz, 1H), 3.94 (s, 3H); 13C NMR (101 MHz, CDCl3) δ 166.91, 136.89, 131.83, 130.13, 129.37, 125.50, 103.35, 52.14, 22.46; EIMS m/z 202.

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