Ethanol → 3-Bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carboxylic acid

Beteiligte Stoffe

Reaktionsschritte

To a 100 mL flask, pentyl 3-bromo-1-(3-chloro-2-pyridinyl)-4,5-dihydro-1H-pyrazole-5-carboxylate (5.00 g, 97%, 12.94 mmol), ethanol (30 mL), water (30 mL) and sodium hydroxide (0.52 g, 12.94 mmol) were added. The reaction mixture was stirred for 6 hours at room temperature. The reaction mixture was concentrated by rotary evaporator to remove ethanol. Then water (250 mL) was added. Aqueous solution was extracted with ethyl acetate (100 mL), acidified with concentrated hydrochloric acid to pH=2 and extracted with dichloromethane (3×200 mL) again. The combined organic layers were dried over anhydrous magnesium sulfate and concentrated by rotary evaporator to give 3-bromo-1-(3-chloro-2-pyridinyl)-1H-pyrazole-5-carboxylic acid (3.60 g) as a white solid in 90% yield. HPLC area normalization method content is 98% (Analytical condition: chromatographic column: ZORBAX Eclipse XDB-C8 4.6×150 mm 5 μm, mobile phase:the ratio of acetonitrile to water is 70:30).

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