Study On The Synthesis Of Several N-heterocyclic Compounds

Nitrogen heterocyclic compounds have recently become an important, fast-growing chemical as a raw material for pharmaceuticals, pesticides, energetic materials etc, and the synthesis of nitrogen heterocyclic compounds seems extraordinarily necessary. In this article, the condensation of aldehyde and amine to six number nitrogen heterocyclic compounds, and the optimization of the process was investigated.First,2-methybenzimidazole,2,3-dimethylbenzo pyrazine,2,3-diethylbenzo pyrazine were prepared. For2-methybenzimidazole, n(acetic acid)/n(o-phenylenediamine)=1.3, and the best reaction temperature and time were100℃and2h, respectively. The highest yield was94%. In addition, NH4Cl was instead of acetic acid and the solvent was CH3OH in the preparation of2,3-dimethylbenzo pyrazine and2,3-diethylbenzo pyrazine. The n(2,3-butoxydione)/n(2,3-butoxydione)/n(0-phenylendiamine) were1.4:4:1and1.4:5:1for2,3-dimethylbenzo pyrazine and2,3-diethylbenzo pyrazine, respectively. The optimal temperatures were both room temperature, and the reaction times were30min and40min. The best yields of2,3-dimethylbenzo pyrazine and2,3-diethylbenzo pyrazine were93%and87%.Second, three complexes azatricycliccompounds2,6-dihydro-pyrido[2,3-b:5,6-b’] diimidazole, pyrazino[2,3-g] quinoxaline and2,3,7,8-dmethyl-pyrazino[2,3-g]quinoxaline were produced. When1,2,4,5-tetraabminobenzene was refluxed for36h in triethyl orthoformate,2,6-dihydro-pyrido[2,3-b:5,6-b’] diimidazole was prepared and the yield was58%. For the production of pyrazino[2,3-g] quinoxaline,1,2,4,5-tetraabminobenzene,glyoxal, and catalyst sodium ethoxide was mixed in the refluxed methanol for0.5h; the yield reached49%. The optimal conditions to synthesize2,3,7,8-dmethyl-pyrazino[2,3-g]quinoxaline was that1,2,4,5-tetraabminobenzene and2,3-butoxydione catalyzed by pyridine were reacted for18h in refluxed toluene, the yield was39%. Moreover, the synthesis method for intermediate2,3,5,6-tetraaminopyridine was improved. The better procedure was that2,6-diamino-3,5-dinitro-pyridine was hydrogenated catalyzed by5%Pd/C in hydrogen pressure at48℃. The reaction solvents were the mixture of methanol and85%H3PO4and the yield was91%.