507462-26-2

General procedure for the synthesis of 5-bromo-3-nitro-1H-pyrrolo[2,3-b]pyridine from 5-bromo-7-azaindole: 5-bromo-1H-pyrrolo[2,3-b]pyridine (470 mg, 2.39 mmol) was added to stirred fuming nitric acid (2.5 mL) in batches at 0 °C. After the addition was completed, the reaction system was kept at 0 °C and stirring was continued for 30 min. Subsequently, the reaction solution was carefully poured into an ice-water mixture (25 mL) and stirred for 30 min. The solid product was isolated by filtration, and the filter cake was washed sequentially with a large amount of deionized water and isohexane, and finally dried under vacuum to afford the target compound 5-bromo-3-nitro-1H-pyrrolo[2,3-b]pyridine (484 mg, 84% yield).

[1] Patent: WO2013/114113, 2013, A1. Location in patent: Page/Page column 23
[2] Patent: US2015/11533, 2015, A1. Location in patent: Paragraph 0101
[3] Patent: WO2018/134254, 2018, A1. Location in patent: Page/Page column 78; 79