To a solution of 5-amino-1H-1,2,4-triazole-3-carboxylic acid (3.9 g, 30.45 mmol) in methanol (100 mL) was slowly added thionyl chloride (SOCl2, 12 g, 100.84 mmol). The reaction mixture was stirred at 70 °C for 48 hours. Upon completion of the reaction, the mixture was concentrated under reduced pressure to remove the solvent. The residue was dissolved in water (100 mL) and the pH was adjusted with saturated sodium bicarbonate (NaHCO3) solution to 8. Subsequently, the aqueous phase was extracted with dichloromethane (3 x 50 mL). The organic layers were combined, dried with anhydrous magnesium sulfate, filtered and concentrated under reduced pressure to afford methyl 5-amino-1H-1,2,4-triazole-3-carboxylate as a white solid (800 mg, 65% yield). The product was confirmed by LC/MS (ES, m/z): [M + H]+ 143.0. 1H NMR (300 MHz, DMSO-d6): δ 3.85 (s, 3H).
