General procedure for the synthesis of 3-chloro-6-bromopyrazin-2-amine from 3,5-dibromo-2-chloropyrazine: 3,5-dibromo-2-chloropyrazine (50.0 g, 184 mmol) and concentrated ammonia (150 mL) were added to a 250 mL sealed tube. The reaction mixture was stirred at 100 °C overnight. Upon completion of the reaction, it was cooled to room temperature and the resulting solid product was collected by filtration. The resulting solid was dried under reduced pressure in an oven to afford 3-chloro-6-bromopyrazin-2-amine as a gray solid (28.0 g, 66% yield), which could be used in subsequent reactions without further purification.
