3-bromo-1H-pyrrolo[3,2-c]pyridine

271-34-1

23612-36-4

Example 1 Synthesis of 3-bromo-5-azaindole Referring to Scheme 1 shown in Figure 1, 5-azaindole (3.0128 g, 25.51 mmol, source: Atlantic SciTech Group) was dissolved in 50 mL of acetonitrile in a 250 mL three-necked round-bottomed flask. The device was equipped with a magnetic stirrer, thermocouple, nitrogen inlet and outlet, and an ice bath cooling system. Solid CuBr2 (17.0 g, 76.53 mmol, 3 eq.) was added in batches over 10 min at 17 °C. The resulting green suspension was stirred at room temperature until the starting material was undetectable by thin layer chromatography (TLC) (ca. 1-2 h; unfolding agent was EtOAc/MeOH = 9:1, 5-azaindole Rf = 0.23, 3-bromo-5-azaindole Rf = 0.49). The reaction mixture was cooled to 10 °C and the reaction was quenched by the slow addition of a methanol solution of 1N ammonia (110 mL). The resulting blue solution was concentrated by rotary evaporation at room temperature and the residue was extracted with ethyl acetate (3 x 80 mL). The organic extract was dried over anhydrous Na2SO4, filtered and concentrated to about 50 mL. The residue was refluxed over heat until all solids were dissolved, followed by addition of hexane to the hot mixture until crystallization occurred. The resulting suspension was cooled in an ice bath, the product was collected by filtration, washed sequentially with cold EtOAc/hexane (1:3) and hexane, and dried to give 3-bromo-5-azaindole as an off-white solid in 3.52 g yield (70% yield).