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

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Reaction Steps

To a 500 mL flask, ethyl 3-bromo-1-(3-chloro-2-pyridinyl)-1H-pyrazole-5-carboxylate (15.00 g, 85%, 38.57 mmol) and ethanol (80 mL) were added. Sodium hydroxide solution (1.54 g, 38.57 mmol, dissolved in water (80 mL)) were added dropwise. The reaction mixture was stirred at room temperature for 2 hours. The mixture was concentrated by rotary evaporator to remove ethanol. The residue was extracted with ethyl acetate (30 mL) and acidified with concentrated hydrochloric acid to pH=3. Aqueous solution was extracted with ethyl acetate (3×100 mL) again. The combined organic layers were washed with saturated brine (100 mL), dried over anhydrous magnesium sulfate and concentrated by rotary evaporator to give the product (10.83 g) as a yellow solid in 91% yield. HPLC area normalization method content is 98%.

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