885520-14-9

5-Fluoro-3-nitro-2-methylaniline (50 mg, 0.294 mmol) was used as starting material and dissolved in acetic acid (AcOH, 10 mL). Aqueous sodium nitrite (3 mL, containing 44.6 mg, 0.588 mmol of sodium nitrite) was slowly added at 0 °C. The reaction mixture was then warmed to room temperature and stirred continuously for 6 hours. The progress of the reaction was monitored by thin layer chromatography (TLC) and the reaction was terminated after confirming the complete consumption of raw materials. The final product 4-nitro-6-fluoroindazole was obtained as 18.3 mg of orange colored powder with 43.5% yield.

[1] Patent: CN108689937, 2018, A. Location in patent: Paragraph 0081; 0082; 0087; 0088
[2] Patent: CN108689936, 2018, A. Location in patent: Paragraph 0048; 0054; 0055
[3] Patent: WO2010/127855, 2010, A1. Location in patent: Page/Page column 153; 154
[4] Patent: WO2014/14794, 2014, A2. Location in patent: Page/Page column 80
[5] Patent: WO2008/110863, 2008, A1. Location in patent: Page/Page column 27