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General procedure for the synthesis of 2-amino-3,5-dibromo-6-methylpyrazine from 2-amino-6-methylpyrazine: In a dry reaction flask, 6-methylpyrazin-2-amine (14.40 g, 132 mmol) and pyridine (26.0 g, 330 mmol) were dissolved in dichloromethane (DCM, 300 mL). A DCM solution of bromine (53.00 g, 330 mmol) was slowly added dropwise at room temperature. After the dropwise addition was completed, the reaction mixture was stirred at room temperature overnight. Upon completion of the reaction, the reaction was quenched by the addition of water (150 mL) and the mixture was transferred to a dispensing funnel for liquid-liquid partitioning. The organic phase was washed with saturated brine (100 mL), dried over anhydrous sodium sulfate and filtered. The filtrate was concentrated in vacuum to afford 2-amino-3,5-dibromo-6-methylpyrazine as a yellow solid (34.01 g, 96% yield). Mass spectrum (ESI, cation mode) m/z: 267.9 [M + H]+.

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