Synthesis
The general procedure for the synthesis of 4-bromo-1H-pyrazole-3-carboxylic acid from pyrazole-3-carboxylic acid was as follows: bromine (800 mg, 5.0 mmol) was slowly added to a solution of pyrazole-3-carboxylic acid (500 mg, 4.5 mmol) in acetic acid (20 mL). The reaction mixture was stirred at room temperature for 18 hours. Upon completion of the reaction, it was diluted with water (100 mL) and extracted with ether (3 x 30 mL). All organic phases were combined, washed with water (50 mL), and the solvent was subsequently removed by concentration under reduced pressure to afford the target product 4-bromo-1H-pyrazole-3-carboxylic acid (750 mg, 87% yield) as a light yellow solid. The structure of the product was confirmed by 1H NMR (DMSO-d6, 400 MHz): δ 7.92 (s, 1H).
References
[1] Patent: WO2006/32851, 2006, A1. Location in patent: Page/Page column 42
[2] J. Gen. Chem. USSR (Engl. Transl.), 1982, vol. 52, # 11, p. 2291 - 2296
[3] Zhurnal Obshchei Khimii, 1982, vol. 52, # 11, p. 2592 - 2598
[4] Patent: WO2017/100591, 2017, A1. Location in patent: Paragraph 00241
