2-Amino-3-nitrobenzoic acid (1.00 g, 5.49 mmol) was dissolved in methanol (40 mL) followed by the addition of concentrated sulfuric acid (0.50 mL). The reaction mixture was heated to reflux for 48 hours. Upon completion of the reaction, the mixture was cooled to room temperature and the pH was adjusted with saturated aqueous sodium bicarbonate to about 9. The mixture was concentrated under reduced pressure to about 10 mL, water (20 mL) was added, and the mixture was extracted with ethyl acetate (10 mL x 3 times). The organic layers were combined and dried with anhydrous magnesium sulfate. The organic layers were concentrated under reduced pressure and the resulting crystals were dried to give methyl 2-amino-3-nitrobenzoate. The product was structurally confirmed by nuclear magnetic resonance hydrogen spectroscopy (1H-NMR). Yield: 661.4 mg (61%). 1H-NMR (270 MHz, CDCl3): δ 8.50 (br, s), 8.37 (1H, dd, J = 8.6, 1.4 Hz), 8.23 (1H, dd, J = 7.6, 1.4 Hz), 6.65 (1H, dd, J = 8.6, 7.6 Hz), 3.92 (3H, s ) ppm.
