875781-43-4

875781-44-5

Step 1. Synthesis of 2-bromo-7-iodo-5H-pyrrolo[2,3-b]pyrazine. To a solution of N,N-dimethylformamide (DMF, 160 mL) of 2-bromo-5H-pyrrolo[2,3-b]pyrazine (8 g, 40.4 mmol) was added N-iodosuccinimide (NIS, 11.8 g, 3.6 mmol) and the reaction mixture was stirred for 1 hour at room temperature. The progress of the reaction was monitored by thin layer chromatography (TLC, unfolding agent ratio of petroleum ether: ethyl acetate = 2:1) to confirm the completion of the reaction. The reaction mixture was diluted with water (500 mL) and extracted with ethyl acetate (EtOAc, 300 mL x 3). The organic phases were combined, washed with saturated saline and dried over anhydrous sodium sulfate (Na2SO4). After filtration, the solvent was removed by concentration under reduced pressure to afford 2-bromo-7-iodo-5H-pyrrolo[2,3-b]pyrazine (26.1 g, 100% yield) as a brown solid (containing a small amount of DMF).