General procedure for the synthesis of 2-amino-3-bromo-5-methylpyrazine from 2-amino-5-methylpyrazine: Bromine (8.80 g, 55.0 mmol) was slowly added to a solution of dichloromethane (250 mL) containing 5-methylpyrazin-2-amine (5.00 g, 45.8 mmol) and pyridine (4.35 g, 55.0 mmol). The reaction mixture was stirred overnight at room temperature. Upon completion of the reaction, water (150 mL) was added to the mixture for extraction and the organic layer was separated. The organic layer was washed with saturated brine (100 mL), dried over anhydrous sodium sulfate and filtered. The filtrate was concentrated under vacuum to afford the target compound 2-amino-3-bromo-5-methylpyrazine as a yellow solid (7.64 g, 88% yield). Mass spectrum (ESI, positive ion mode) m/z: 190.2 [M + H]+; 1H NMR (400 MHz, CDCl3) δ (ppm): 7.83 (s, 1H), 4.93 (s, 2H), 2.41 (s, 3H).
