4-Bromo-1H-pyrrolo[2,3-b]pyridine (XCI) (5 g, 25.4 mmol, 1 eq.) was used as a starting material, which was dissolved in dichloromethane (DCM) (100 mL), 4-dimethylaminopyridine (DMAP) (311 mg, 2.55 mmol, 0.1 eq.) and triethylamine (TEA) (5.3 mL) were added. Di-tert-butyl dicarbonate (Boc2O) (7.2 mL, 31 mmol, 1.2 eq.) was slowly added to the reaction mixture at 0 °C. The reaction system was gradually warmed to room temperature and stirred continuously for 2 hours. Upon completion of the reaction, it was quenched by addition of water (100 mL) and extracted twice with dichloromethane (DCM). The organic phases were combined and concentrated under reduced pressure to remove the solvent to afford tert-butyl 4-bromo-1H-pyrrolo[2,3-b]pyridine-1-carboxylate (XCII) as a colorless oil (6.95 g, 23.4 mmol, 92.1% yield). The product was confirmed by 1H NMR (CDCl3, 400 MHz): δ 1.60 (s, 9H), 6.50 (d, J = 4 Hz, 1H), 7.31 (d, J = 5.2 Hz, 1H), 7.63 (d, J = 4 Hz, 1H), 8.23 (d, J = 5.2 Hz, 1H); electrospray ionization mass spectrometry (ESIMS) analysis showed molecular ion peaks m/z 297.1 (M + H), consistent with the expected molecular formula C12H13BrN2O2.
![tert-Butyl 4-broMo-1H-pyrrolo[2,3-b]pyridine-1-carboxylate](/CAS/20150408/GIF/1228014-35-4.gif)