To a solution of 3-aminopyridine-2-carboxylic acid (20 g, 144.9 mmol) in methanol (300 mL) was added conc. sulfuric acid (5.4 mL), and the mixture was heated under reflux for 5 days. The reaction mixture was concentrated under reduced pressure, water was added thereto, and sodium carbonate was added thereto until the complete of foaming. The mixture was extracted with dichloromethane (x3), the organic layer was dried over sodium sulfate, and the solvent was evaporated under reduced pressure to give methyl 3-aminopyridine-2-carboxylate (17.0 g, 77%) as a pale yellow solid. 1H-NMR(300MHz,CDCl3):|?3.95(3H,s),5.72(2H,brs),7.03(1H,dd,J=0.99,8. 35Hz),7.18-7.21(1H,m),8.05(1H,dd,J=0.96,4.04Hz).
