Butylamine → N,N-dibutyl-4-chloro-5-methyl-1H-pyrazole-3-carboxamide

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To a solution of n-butylamine (900 μL, 5.30 mmol) in THF (4.0 mL) was added n-BuLi (5.0 mL, 7.95 mmol, 2.5M solution in hexanes) at −78° C. After stirring at −78° C. for 30 min, a solution of ethyl 4-chloro-5-methyl-1H-pyrazole-3-carboxylate (500 mg, 2.65 mmol) in 2.0 mL of THF was added dropwise via syringe. The reaction mixture was allowed to warm to room temperature overnight and quenched with sat. aq. NH4Cl solution. The aqueous layer was extracted with CH2Cl2 (3×), and the combined organic extracts were dried over Na2SO4, filtered and concentrated in vacuo to give a crude oil. Purification using flash column chromatography (gradient from 0% to 7% MeOH/CH2Cl2) provided the title compound (589 mg, 82%) as a colorless oil. 1H NMR (CD3OD) δ 3.51 (t, J=7.4 Hz, 2H), 3.38-3.32 (m, 2H), 1.68-1.62 (m, 2H), 1.56-1.50 (m, 2H), 1.45-1.38 (m, 2H), 1.22-1.15 (m, 2H) 0.98 (t, J=7.4 Hz, 3H), 0.81 (t, J=7.4 Hz, 3H); MS(ESI+) m/z 272.1 (M+H)+.

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