Step 2: Methyl 3-aminopyridine-2-carboxylate (17 g, 111.8 mmol) was dissolved in a solvent mixture of water (288 mL) and 2M sulfuric acid (58 mL) and stirred at room temperature until completely dissolved. Subsequently, a solution of bromine (5.76 mL, 111.8 mmol) in acetic acid (43 mL) was added slowly dropwise, and the reaction continued to be stirred at room temperature for 4 hours after completion of the dropwise addition. Upon completion of the reaction, the pH of the reaction mixture was adjusted to 6 with 2N aqueous sodium hydroxide solution. the aqueous phase was extracted twice with ethyl acetate (in equal amounts each time), the organic layers were combined and dried over anhydrous sodium sulfate. The organic solvent was removed by evaporation under reduced pressure to give the crude product. The crude product was purified by silica gel column chromatography using dichloromethane as eluent to afford methyl 3-amino-6-bromopyridine-2-carboxylate (19.2 g, 74% yield) as a white solid. The product was characterized by 1H-NMR (300 MHz, CDCl3): δ 3.94 (3H, s), 5.81 (2H, brs), 6.93 (1H, d, J = 8.72 Hz), 7.32 (1H, d, J = 8.71 Hz).
