5-Nitroindazole inhibits citrulline formation by Ca2+-calmodulin (CaM)-dependent nitric oxide synthase from bovine brain. Nitration of 5-nitroindazole with nitric acid and acetic anhydride yields 3,5-dintroindazole and 2,5-dinitroindazole.
General procedure: hydrazine hydrate (NH2NH2-H2O, 3.0 mmol) was added dropwise to a stirred solution of 2-fluoro-5-nitrobenzaldehyde (1.0 mmol) in DMF (5 mL) at 23 °C. The reaction mixture was stirred continuously at the same temperature for 2 h. The progress of the reaction was monitored by thin-layer chromatography (TLC, unfolding agent: 20% ethyl acetate in hexane solution) to confirm the complete conversion of the starting material 2-fluoro-5-nitrobenzaldehyde. Upon completion of the reaction, the crude reaction mixture was poured into water and extracted with ethyl acetate (2 x 15 mL). The organic phases were combined, washed sequentially with water and saturated aqueous sodium chloride, dried over anhydrous magnesium sulfate, filtered and concentrated under reduced pressure to give pure 5-nitroindazole.
[1] Molecules, 2018, vol. 23, # 3,
[2] Organic Process Research and Development, 2011, vol. 15, # 3, p. 565 - 569
