Studied On The Synthesis Of The Five-or Six-membered Heterocycles Containing Nitrogen

Nitrogen-containing heterocyclic compounds represent a large class of important compounds, its derivatives are widely existed in biomass and modern chemical medicine. Therefore, the synthesis of five or six membered nitrogen-containing heterocyclic compounds has attracted great attention of chemical workers to research in this field. This paper summarized the application of nitroolefins in organic transformations in term of 1,3-dipolarcyclization reactions, Michael addition reactions, alkylation reactions and Diels Alder reactions. We also have summarized the synthetic methods of imidazole derivatives based on different skeletal structures and classified the synthesis of 1,2,4-triazine compounds from different reagents.We have researched on new methods for the synthesis of imidazole derivatives and 1,2,4-triazine compounds, which focus on the construction of C-N bond by oxidative coupling and cyclization reactions via nucleophilic strategies. Aryl amidines and nitroethylenes are treated with cuprous iodide, bipyridyl and oxygen in DMF at 90 oC for 5 hours to generate multi-substituted imidazole compounds, and the reactions exhibit good regioselectivity without using expensive catalysts. Aryl amidines and aryl ketones are performed in presence of divalent copper catalytic species, lewis acids and nitrogen ligands to afford multi-substituted imidazoles, and these reactions show good functional groups tolerance as well as good yields. A mixture of α-aminoketone compounds, aldehydes and ammonium acetate are treated with a catalytic amount of iodine with ethanol as solvent at 40 oC overnight to give trisubstituted imidazole compounds, and the strategy demonstrated mild reaction conditions and simple operation. Amidrazones and aryl ketones are treated with the oxidant selenium dioxide with dimethylsulfoxide as solvent at 110 oC to synthesize 3,5-substituted 1,2,4-triazine compounds in one-pot. Amidrazones and aryl-alkynes are also treated with N-iodosuccinimide(NIS) as a source of iodine, p-toluenesulfonic acid(TsOH) and dimethylsulfoxide as solvent at 110 oC to give 3,5-substituted 1,2,4-triazine in onepot. These strategies could start with simple materials to give the desired products, otherwise, this type of reactions have good application in the biomedical field.