1060812-84-1

The general procedure for the synthesis of 5-bromopyrazolo[1,5-a]pyridine-3-carboxylic acid from ethyl 5-bromopyrazolo[1,5-a]pyridine-3-carboxylate was as follows: ethyl 5-bromopyrazolo[1,5-a]pyridine-3-carboxylate (240 mg, 0.89 mmol) was dissolved in 40% H2SO4 (12 mL), and the reaction was stirred for 4 hours at 100 °C. After completion of the reaction, the mixture was cooled to room temperature and cooled with an ice bath. Subsequently, aqueous 6 M NaOH was slowly added to neutralize to pH=7. The reaction mixture was extracted with dichloromethane (DCM, 25 mL x 2). The organic phases were combined, dried over anhydrous Na2SO4 and concentrated under reduced pressure to afford 5-bromopyrazolo[1,5-a]pyridine as a light yellow solid (175 mg, 99.5% yield). Mass spectrum (ESI, cation mode) m/z: 196.9 [M + H]+.

[1] Patent: US2014/234254, 2014, A1. Location in patent: Paragraph 0329; 0330; 0341; 0342
[2] Bioorganic and Medicinal Chemistry, 2012, vol. 20, # 1, p. 69 - 85
[3] Patent: WO2014/78802, 2014, A1. Location in patent: Page/Page column 158
[4] Patent: WO2014/8197, 2014, A1. Location in patent: Page/Page column 136
[5] Patent: WO2015/95767, 2015, A1. Location in patent: Page/Page column 151