885520-23-0

4-Bromo-2,6-difluorobenzaldehyde (CAS 537013-51-7, 442.0 mg, 2.00 mmol) was suspended in ethylene glycol (10 mL) at room temperature, and hydrazine monohydrate (0.19 mL, 4.00 mmol) was slowly added with stirring. The reaction mixture was heated to 95 °C under nitrogen protection and maintained at this temperature for 2 hours. Upon completion of the reaction, the mixture was cooled to 5 °C and diluted with deionized water. Subsequently, the reaction solution was extracted with ethyl acetate, the organic phase was dried with anhydrous sodium sulfate and concentrated under reduced pressure to afford the target product 6-bromo-4-fluoro-1H-indazole (430.0 mg, 100% yield) as a yellow solid.

[1] Bioorganic and Medicinal Chemistry, 2016, vol. 24, # 23, p. 6194 - 6205
[2] Journal of Medicinal Chemistry, 2017, vol. 60, # 7, p. 3187 - 3197
[3] Patent: US2015/99782, 2015, A1. Location in patent: Paragraph 0225; 0226