Sodium Hydroxide → 3-bromo-1-(3-chloro-2-pyridinyl)-4,5-dihydro-1H-pyrazole-5-carboxylic acid

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Reaction Steps

To a 500 mL flask, ethyl 3-bromo-1-(3-chloro-2-pyridinyl)-4,5-dihydro-1H-pyrazole-5-carboxylate (20 g, 93%, 55.92 mmol), ethanol (100 mL) were added. The solution of sodium hydroxide (2.34 g, 58.50 mmol, dissolved into water (100 mL)) was added dropwise. After being stirred for 2 hours at room temperature, the reaction mixture was concentrated by rotary evaporator to remove ethanol. Aqueous solution was extracted with ethyl acetate (30 mL) and acidified with concentrated hydrochloric acid to pH=3. Then aqueous solution was extracted with ethyl acetate (3×100 mL) again. The organic layers were washed with saturated brine (100 mL), dried over anhydrous magnesium sulfate and concentrated by rotary evaporator to give 3-bromo-1-(3-chloro-2-pyridinyl)-4,5-dihydro-1H-pyrazole-5-carboxylic acid (16.67 g) as a yellow solid in 92% yield. HPLC area normalization method content is 94% (Analytical condition: chromatographic column: ZORBAX Eclipse XDB-C84.6×150 mm 5 μm, mobile phase:the ratio of acetonitrile to water is 70:30).

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