Hydrochloric Acid → 4-Amino-2-fluoro-3-methylbenzoic acid

In 7 ml of ethanol was suspended 0.70 g of ethyl 4-amino-2-fluoro-3-methylbenzoate, followed by adding thereto 7 ml of lN sodium hydroxide, and the resulting mixture was stirred at 40° C. for 4 hours. To the reaction mixture was added 1.2 ml of 6N hydrochloric acid, followed by extraction with 50 ml of ethyl acetate. The extract solution was washed with a saturated aqueous sodium chloride solution, dried over anhydrous magnesium sulfate, and then distilled under reduced pressure to remove the solvent, to obtain 0.59 g of 4-amino-2-fluoro-3-methylbenzoic acid as colorless crystals.