Hydrochloric Acid → N-(1-(2,4-difluorophenyl)-1H-pyrazol-5-yl)acetamide

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A solution of 1-(2,4-difluorophenyl)-1H-pyrazol-5-amine (5.00 g, 26 mmol), in 80 mL of 1,2-DCE was added DMAP (0.94 g, 7.7 mmol), Ac2O (12 mL, 128 mmol) and Et3N (18 mL, 128 mmol). The dark brown reaction mixture was heated at 80° C. in an oil bath for 18 h. After cooling to RT, it was diluted with 20 mL of DCM and washed with saturated aqueous solution of sodium bicarbonate, and brine. The resulting organic solution was then dried over magnesium sulfate and concentrated under reduced pressure to give viscous brown oil which contains the bis-acylated product along with residual amount of Ac2O and AcOH. The viscous brown oil was dissolved in 50 mL of EtOH and treated with KOH (5.0 g 129 mmol). After the reaction mixture was stirred at RT for 4 h, it was acidified with 2 N HCl to pH 4. The volatile portion was removed on the rotovap. The residue was diluted with 150 mL of EtOAc, washed with saturated aqueous solution of sodium bicarbonate, and brine. The resulting organic solution was then dried over magnesium sulfate and concentrated under reduced pressure. Purification of the crude material on an ISCO 80 g column (60-100% EtOAc in hexanes) afforded N-(1-(2,4-difluorophenyl)-1H-pyrazol-5-yl)acetamide as an off-white solid. MS (ES+): 238.1 (M+H)+.

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