General procedure for the synthesis of methyl 3-amino-6-iodopyrazine-2-carboxylate from methyl 3-aminopyrazine-2-carboxylate: 1.5 equivalents of N-iodosuccinimide (NIS) was added to a 25 mL solution of dimethylformamide (DMF) containing 5 g (32.7 mmol) of methyl 3-aminopyrazine-2-carboxylate at room temperature. The reaction mixture was heated to 65 °C and after 1 hour of reaction, 0.5 equivalents of N-iodosuccinimide (NIS) was added and the reaction was continued at 65 °C for 24 hours. After completion of the reaction, the mixture was cooled to room temperature and the solvent was removed by rotary evaporation. Subsequently, the product was extracted several times with dichloromethane. The organic phases were combined, washed with 10% sodium bisulfite solution, dried over anhydrous magnesium sulfate, and concentrated to give 8 g (88% yield) of the yellow solid product methyl 3-amino-6-iodopyrazine-2-carboxylate. The product was analyzed by LC-MS (EI) at m/z (M+1) of 280. 1H NMR (400 MHz, DMSO-d6) δ: 8.50 (1H, s, Ar-H), 7.50 (2H, br s, NH2), 3.20 (3H, s, OCH3).
