The general procedure for the synthesis of 3-methoxy-4-fluorobenzoic acid from methyl 4-fluoro-3-methoxybenzoate was as follows: methyl 4-fluoro-3-methoxybenzoate (11 g, 59.8 mmol) was dissolved in methanol (100 mL), and a solution of sodium hydroxide (9.5 g, 240 mmol) in water (20 mL) was added, and the reaction was stirred for 4 h at room temperature. Upon completion of the reaction, the solvent was removed by distillation under reduced pressure to give a residue. The residue was dissolved in water (100 mL) and the pH was adjusted with 1N HCl solution to 4. Subsequently, the precipitated solid was collected by filtration, washed with water (3 x 50 mL), and dried to give 3-methoxy-4-fluorobenzoic acid as a white solid (9 g, 97% yield). The product was characterized by 1H-NMR (300 MHz, DMSO-d6): δ 7.66-7.55 (m, 2H), 7.37-7.30 (m, 1H), 3.91 (s, 3H).
