SOCl2 (10.4 g, 86.9 mmol) was slowly added dropwise to a stirred methanolic solution (100 mL) of 5-aminonicotinic acid (10.0 g, 72.5 mmol) at 0 °C. After gradually warming the reaction mixture to room temperature, the reaction was continued at reflux for 16 hours. After completion of the reaction, the mixture was cooled and concentrated under vacuum. The residue was diluted with deionized water (200 mL) and subsequently neutralized with aqueous NaHCO3 to pH=7. The aqueous phase mixture was extracted with dichloromethane (DCM, 100 mL x 2). The organic layers were combined, washed with saturated saline (100 mL × 2), dried over anhydrous Na2SO4, filtered, and the filtrate was concentrated to dryness under vacuum to give 9.5 g of methyl 5-aminopyridine-3-carboxylate as a white solid in 86% yield. The product was characterized by 1H NMR (DMSO-d6, 400 MHz): δ=8.24 (1H, d), 8.12 (1H, d), 7.42 (1H, dd), 5.65 (2H, brs), 3.84 (3H, s).
