Abstract: Azabicyclo compounds of 1,4-benxodiazine, pyrido[2,3-b]pyrazine, 1H-benzimidazole, 3H-imidazo-[4,5-b]pyridine were prepared from o-phenylenediamine or 2,3-diaminopyridine reacted with carbonyl compounds. The effects of reaction medium, pH, time and other factors on the reactions were invesitigated. The results showed that the yield of pyrido[2,3-b]pyrazine could reach 89.4% when refluxed in propanol for 1 h at pH=9 adjusted by methanol sodium. The yields for 1,4-benxodiazine could be increased to 98.3% in aqueous medium with pH=9 adjusted by sodium sulfite at 60 ℃ after 40 min reaction. Here, the purification of target product could be achieved via a low temperature standing process instead of the vacuum distillation method. The optimized conditions for the other two compounds are: refluxing o-phenylenediamine for 2 h in 88% formic acid solution yielding 1H-benzimidazole with 92% yield; refluxing 2,3-diaminopyridine with triethoxy methane for 3 h followed by adding concentrated hydrochloric acid for another 1 h giving 3-H-imidazo[4,5-b]pyridine with 84.2% yield.

Key words: Azabicyclo compounds, synthesis, condensation