3537-09-5

5-Nitropyridine-2,3-diamine (0.050 g, 0.32 mmol) was dissolved in formic acid (10 mL), heated to 100 °C and kept for 6 h. The reaction was completed with aqueous phase (10 mL). After completion of the reaction, the reaction mixture was diluted with water (10 mL) and the pH was adjusted with 3N NaOH solution to 7. The aqueous phase was extracted six times with a 25% isopropanol (IPA)/dichloromethane (DCM) solvent mixture, and the organic phases were combined, dried with anhydrous Na2SO4, and concentrated under reduced pressure to afford 6-nitro-3H-imidazo[4,5-b]pyridine (52 mg, 98% yield) as a solid.

[1] Patent: WO2009/111277, 2009, A1. Location in patent: Page/Page column 53
[2] Bioorganic and Medicinal Chemistry Letters, 2013, vol. 23, # 21, p. 5896 - 5899