68175-07-5

452-58-4

64-19-7

68175-07-5

General procedure: a solution of 2,3-diaminopyridine (45.8 mmol) and glacial acetic acid (458.0 mmol) in polyphosphoric acid (50 ml) was placed under nitrogen protection, heated to 135-140°C and maintained for 2-4 hours. After completion of the reaction, the reaction mixture was cooled and poured slowly into 250 ml of cold water, activated carbon was added and filtered through a bed of diatomaceous earth. The filtrate was adjusted to pH 10-12 with aqueous ammonia solution. the alkalized aqueous phase was extracted with ethyl acetate (250 ml x 3), the organic phases were combined and dried with anhydrous sodium sulfate. The solvent was removed by distillation under reduced pressure to give the crude product. Hexane (50 ml) was added to the crude product and the solid was collected by filtration to give 2-methyl-3H-imidazo[4,5-b]pyridine (XI and XII).