4-Bromo-6-fluoro (1H)indazole

1093066-65-9

885520-70-7

1-Bromo-5-fluoro-2-methyl-3-nitrobenzene (7.49 g, 31.8 mmol) was used as a raw material, which was dissolved in dioxane (40 mL) and then DMF-DMA (21.0 mL, 158 mmol) and pyrrolidine (2.6 mL, 31.1 mmol) were added sequentially. The reaction mixture was heated at 100 °C for the reaction. After completion of the reaction, the mixture was cooled to room temperature and concentrated under reduced pressure to remove the solvent to afford 1-[2-(2-bromo-4-fluoro-6-nitrophenyl)-1-methylethenyl]-pyrrolidine as a dark red residue (10.0 g, theoretical amount). This pyrrolidine derivative (10.0 g, 31.7 mmol) was mixed with Raney nickel (suspended in water, 15 mL) in MeOH:THF (1:1, 150 mL), and hydrazine monohydrate (2.3 mL, 47.4 mmol) was added slowly at 0 °C, followed by stirring the mixture for 5 h at room temperature. Upon completion of the reaction, the reaction mixture was filtered through diatomaceous earth and the filter cake was washed with EtOAc. The filtrates were combined and concentrated to dryness under reduced pressure to afford the title compound 4-bromo-6-fluoro-1H-indole as a light colored oil (2.57 g, 37% yield). NMR hydrogen spectrum (300 MHz, CDCl3) δH 6.57 (apparent triple peak, J = 2.7 Hz, 1H), 7.04 (double-double peak, J = 2.1, 9.1 Hz, 1H), 7.12 (double-double peak, J = 2.1, 9.1 Hz, 1H), 7.20-7.25 (multiple peaks, 1H), 8.25 (single peak, 1H).