5-Chloro-1H-pyrrolo[2,3-b]pyridine-7-oxide (5.00 g, 29.66 mmol) was used as a raw material, which was dissolved with tetrabutylammonium bromide (Bu4Br, 19.12 g, 59.31 mmol) in N,N-dimethylformamide (DMF, 200 mL). Trifluoromethanesulfonic anhydride (Tf2O, 20.91 g, 74.20 mmol) was slowly added dropwise to the above solution at 0 °C. After the dropwise addition, the reaction mixture was stirred at room temperature for 2 hours. Subsequently, the reaction solution was poured into water (500 mL), and the pH of the mixture was adjusted to 8-9 with saturated aqueous sodium bicarbonate (NaHCO3). The precipitate was collected by filtration, and the filter cake was washed with water (50 mL x 3) and dried under vacuum at 60 °C overnight to afford 4-bromo-5-chloro-1H-pyrrolo[2,3-b]pyridine as an off-white solid (5.83 g, yield 84.9%). Mass spectrum (ESI, positive ion mode) m/z: 231.0 [M + H]+; NMR hydrogen spectrum (400 MHz, DMSO-d6) δ (ppm): 12.24 (s, 1H), 8.30 (s, 1H), 7.68 (s, 1H), 6.45 (s, 1H).
![1H-pyrrolo[2,3-b]pyridine, 5-chloro-, 7-oxide](/CAS/GIF/916176-51-7.gif)
![4-Bromo-5-chloro-1H-pyrrolo[2,3-b]pyridine](/CAS/20150408/GIF/916176-52-8.gif)