General procedure for the synthesis of methyl 2-fluoro-4-hydroxybenzoate from methanol and 2-fluoro-4-hydroxybenzoic acid: Referring to Example 10 of the literature; 2-fluoro-4-hydroxybenzoic acid (50.0 g) was dissolved in methanol (700 mL), concentrated sulfuric acid (10 mL) was added as a catalyst, and the reaction was carried out with heating and stirring for 16 hrs. at 90 °C. After the reaction was completed, the reaction solution was concentrated, and the resulting colorless crystals were washed with water and dried to obtain the target product methyl 2-fluoro-4-hydroxybenzoate (51 g, 94% yield) as colorless crystals. The product was characterized by 1H NMR (300 MHz, DMSO-d6): δ 3.79 (3H, s), 6.61-6.72 (2H, m), 7.73-7.79 (1H, m), 10.80 (1H, br).
