General procedure for the synthesis of methyl 6-amino-2-pyrazinecarboxylate from methyl 6-chloropyrazine-2-carboxylate: methyl 6-chloropyrazine-2-carboxylate (2 g, 0.0115 mol) was dissolved in 80 mL of dimethylsulfoxide (DMSO). To this solution, sodium azide (3 g, 0.0463 mol) and triphenylphosphine (4.6 g, 0.01738 mol) were sequentially added, followed by refluxing the reaction mixture at 120 °C for 4 hours. Upon completion of the reaction, 20 mL of 1 N hydrochloric acid solution was added to the mixture and the reaction was continued at 120 °C for 2 hours. At the end of the reaction, the mixture was cooled to room temperature and neutralized with aqueous sodium bicarbonate solution, followed by extraction of the target product with ethyl acetate. The organic phase was dried with anhydrous sodium sulfate, filtered and concentrated, and the residue was washed with n-pentane to give 1.4 g of methyl 6-amino-2-pyrazinecarboxylate as a yellow solid in 82.4% yield. The product was characterized by 1H NMR (400 MHz, DMSO-d6): δ 8.28-8.27 (m, 1H), 8.07 (s, 1H), 6.90 (s, 2H), 3.84 (s, 3H). Molecular weight of the molecular formula C6H7N3O2 is 153.14; mass spectrum (ESI) m/z: [M + H]+: 154.05.
