5-Chloro-3H-imidazo[4,5-b]pyridine

40851-95-4

122-51-0

52090-89-8

The reaction was carried out at reflux for 5 hours using 6-chloro-2,3-diaminopyridine (350 g, 2.44 mol) and triethyl orthoformate (2100 g, 14.2 mol) with the addition of p-toluenesulfonic acid monohydrate (46.5 g, 0.244 mol) as a catalyst. The reaction process was monitored by thin layer chromatography (TLC). After completion of the reaction, the reaction solution was concentrated and the crude product was purified by fast column chromatography to afford 5-chloro-3H-imidazo[4,5-B]pyridine (222 g, 1.45 mol) in 59% yield. The structure of the product was confirmed by nuclear magnetic resonance (NMR) spectroscopy (Figure 3).