Hydrochloric Acid → 3-(1H-pyrazol-5-yl)-1-[3-(trifluoromethyl)phenyl]pyridazin-4(1H)-one

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A solution of 3-[3-(dimethylamino)prop-2-enoyl]-1-[3-(trifluoromethyl)phenyl]pyridazin-4(1H)-one (2.70 g, 8 mmol) and NH2NH2.H2O (1.94 mL, 40 mmol) in MeOH (25 mL) was refluxed overnight. After cooling to room temperature, the reaction mixture was poured into 1 M HCl aqueous solution and extracted with AcOEt. The extract was washed with brine, dried over MgSO4, and concentrated under reduced pressure. The residue was purified by basic silica gel column chromatography eluting with AcOEt and recrystallized from AcOEt to give the title compound (0.969 g, 40% yield) as an off-white solid: mp 192-194° C.; NMR (300 MHz, CDCl3): δ ppm 6.82 (1H, d, J=7.9 Hz), 7.03 (1H, d, J=1.9 Hz), 7.69 (1H, d, J=1.9 Hz), 7.72-7.76 (2H, m), 7.83-7.89 (1H, m), 7.91-7.93 (1H, m), 8.33 (1H, d, J=7.9 Hz), 12.85 (1H, brs). LC-MS (ESI) m/z 307 [M+H]+. Anal. Calcd for C14H9F3N4O: C, 54.91; H, 2.96; N, 18.29. Found: C, 54.92; H, 2.99; N, 18.33.

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