Abstract
Azabicyclo compounds of 1,4-benxodiazine,pyridopyrazine,1H-benzimidazole,3H-imidazopyridine 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 pyridopyrazine 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 3H-imidazopyridine with 84.2% yield.
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