2-Dimethylaminopyridine → tert-Butyl 3-bromo-1H-pyrrolo[3,2-c]pyridine-1-carboxylate

Referring now to the Scheme 1 as shown in FIG. 1, a solution of 3.5601 g (18.06 mmol) of 3-bromo-5-azaindole (2) and 0.4651 g (3.8 mmol, 21 mol %) of dimethylaminopyridine (DMAP) in 80 mL of THF was placed in a 250 mL three-neck round-bottom flask equipped with a magnetic stirrer, thermocouple, nitrogen bleed, and cooling ice bath. A total of 4.7769 g (21.88 mmol, 1.2 eq.) of BOC2O was added to the flask at 17° C., and the resulting mixture was stirred until starting 3-bromo-5-azaindole disappeared, as monitored by TLC (generally, overnight stirring at room temperature). The resulting yellow solution was concentrated on rotavap, washed with 100 mL of saturated sodium bicarbonate, and extracted with dichloromethane (3×80 mL). The organic phase was dried over Na2SO4 and concentrated on rotavap to afford 6.57 g of orange solid. This crude material was purified on CombiFlash using hexane/ethyl acetate as eluent to give 5.25 g (97% yield) of n-boc-3-bromo-5-azaindole (3) as a white solid.