To a suspension of 2-methylaminoacetonitrile hydrochloride (20 g, 142.0 mmol) in dichloromethane (DCM, 1300 mL) was slowly added oxalyl bromide (54 mL, 188.67 mmol), followed by the dropwise addition of N,N-dimethylformamide (DMF, 1.5 mL) at 0 °C. The reaction mixture was warmed to 55 °C and stirred for 16 hours. Upon completion of the reaction, the dichloromethane was removed by distillation under reduced pressure and the crude product obtained was purified by column chromatography using 2% methanol/dichloromethane (MeOH/CH2Cl2) as eluent to afford the target compound 3,5-dibromo-1-methylpyrazin2(1H)-one as a light yellow solid (34 g, 92% yield). The structure of the product was confirmed by 1H NMR (400 MHz, DMSO-d6): δ 8.1 (s, 1H), 3.4 (s, 3H).LC-MS analysis showed the molecular ion peak m/z 268.9 ([M + 1]+).
