875781-17-2

5-Bromo-1H-pyrazolo[3,4-b]pyridine is a pyridine (P998910) derivative and useful building block, seen in its use in the synthetic preparation of 7-?azaindazole chalcone derivatives as analgesics and anti-?inflammatories.

The general procedure for the synthesis of 5-bromo-1H-pyrazolo[3,4-b]pyridine from 5-bromo-2-fluoro-3-formylpyridine was as follows: preparation of 5-bromo-1H-pyrazolo[3,4-b]pyridine (D-1-3). Compound D-1-2 (20 g, 0.1 mol) was mixed with an ethanol solution of anhydrous hydrazine (18 g, 0.56 mol) and heated to reflux overnight. The progress of the reaction was monitored by thin layer chromatography (TLC, unfolding agent was petroleum ether/ethyl acetate, 2:1, v/v) to confirm complete consumption of the raw material. Upon completion of the reaction, the reaction mixture was concentrated under vacuum to about 50 mL and subsequently poured into water (500 mL). The resulting mixture was filtered and the filter cake was washed sequentially with water (50mL x 3) and ether (20mL x 3). Finally, the filter cake was dried under vacuum to afford the target compound D-1-3 (9.0 g, 46% yield) as a yellow solid.

[1] Journal of Organic Chemistry, 2017, vol. 82, # 14, p. 7420 - 7427
[2] Patent: WO2009/16460, 2009, A2. Location in patent: Page/Page column 99-100
[3] Patent: WO2014/73904, 2014, A1. Location in patent: Paragraph 1496-1499
[4] Patent: CN103980272, 2016, B. Location in patent: Paragraph 0031; 0033
[5] Patent: WO2017/23987, 2017, A1. Location in patent: Paragraph 0610; 0612