Synthesis
General procedure for the synthesis of 5-bromo-6-fluoro-1H-indazole from 1-(5-bromo-6-fluoro-1H-indazol-1-yl)ethanone: 1-(5-bromo-6-fluoro-1H-indazol-1-yl)ethanone (1.58 g, 6.15 mmol) was dissolved in a solvent mixture of a 3M HCl aqueous solution (20 mL) and methanol (4 mL). The reaction mixture was heated to reflux at 90 °C for 3 hours. Upon completion of the reaction, it was cooled to room temperature and the pH was adjusted to 10 with 1 M NaOH aqueous solution. at this point, a colorless solid precipitated from the solution, which was collected by filtration and dried under vacuum to afford the target product 5-bromo-6-fluoro-1H-indazole (1.22 g, 93% yield). The 1H NMR (CDCl3) data of the product were as follows: δ 9.0-10.20 (1H, br), 8.02 (1H, s), 7.97 (1H, d, J = 6.4 Hz), 7.28 (1H, s).
References
[1] Patent: WO2012/103806, 2012, A1. Location in patent: Page/Page column 55
[2] Patent: WO2006/44860, 2006, A2. Location in patent: Page/Page column 37-38
[3] Patent: US2016/347717, 2016, A1. Location in patent: Paragraph 0619; 0620
[4] Patent: WO2009/32123, 2009, A2. Location in patent: Page/Page column 179-180
[5] Patent: WO2009/32125, 2009, A1. Location in patent: Page/Page column 119
