General procedure for the synthesis of 5-bromo-3-iodopyrazin-2-amine from 2-amino-5-bromopyrazine: To a solution of 2-amino-5-bromopyrazine (10.0 g, 57.47 mmol) in 1,4-dioxane (100 mL) was added N-iodosuccinimide (15.5 g, 68.96 mmol). The reaction mixture was heated to 80 °C and kept for 16 h. After cooling to room temperature, the 1,4-dioxane was removed by concentration under reduced pressure by rotary evaporator. To the residue, 50 mL of water was added and extracted with dichloromethane (50 mL x 4), the organic phases were combined and washed with distilled water (20 mL x 3), dried over anhydrous sodium sulfate and concentrated under reduced pressure to obtain the crude product. The crude product was purified by fast column chromatography with the eluent being a petroleum ether solution of 20-30% ethyl acetate to give the final target compound 5-bromo-3-iodopyrazin-2-amine (4.3 g, 25.1% yield).1H NMR (400 MHz, DMSO-d6): δ 8.05 (s, 1H), 6.76 (s, 2H).
