Methyl 4-amino-2-hydroxybenzoate (50.7 g, 303.6 mmol) was dissolved in ethyl acetate (750 mL) with stirred water (250 mL) and sodium bicarbonate solution (34.9 g). The mixture was cooled to 0°C over 15 minutes, followed by slow dropwise addition of acetyl chloride (29.7 mL, 415.5 mmol). The reaction mixture was gradually warmed to room temperature and stirred continuously for 2 hours. After completion of the reaction, the organic and aqueous layers were separated, the organic layer was washed with brine and dried over anhydrous sodium sulfate. The solvent was removed by concentration under reduced pressure to give the white solid product methyl 4-acetamido-2-hydroxybenzoate (63.5 g, 99% yield). The product was confirmed by NMR hydrogen spectrum (CDCl3): δ10.86 (broad single peak, 1H), 7.78 (double peak, J=8.6Hz, 1H), 7.23 (single peak, 1H), 7.16 (broad single peak, 1H), 7.10 (double peak, J=8.6Hz, 1H), 6.13 (broad single peak, 1H), 3.92 (single peak, 3H), 2.19 ( single peak, 3H); mass spectrum (m/z): 208 (MH)+.
