Hydrochloric Acid → 5-(2-chloro-4-fluorophenyl)-1,3-dimethyl-1H-pyrazole-4-carboxylic acid

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A mixture of methyl 5-(2-chloro-4-fluorophenyl)-1,3-dimethyl-1H-pyrazole-4-carboxylate (i.e. the product of Step C) (12.33 g, 43.7 mol) and sodium hydroxide (1 N, 70 mL) in methanol (70 mL) was heated at reflux for 2 h. The reaction mixture was cooled to about 0° C., and then the pH of the reaction mixture was adjusted to 3 by the addition of aqueous hydrochloric acid solution (1 N). The reaction mixture was extracted with ethyl acetate (3×70 mL) and the combined extracts were washed with saturated aqueous sodium chloride solution, dried over magnesium sulfate and filtered. The filtrate was concentrated under reduced pressure to provide the title compound as a white solid (11.14 g).

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