Study On The Synthesis And Characterization Of N-Heterocyclic Compounds Via Multi-component Reactions

N-Heterocyclic compounds is an important class of heterocycles species, therefore, efficient synthesis of N-heterocyclic compounds is the focus of research interests of organic chemists. In recent years, multi-component reactions (MCRs), which response to the simple procedure, efficiency and superior atom economy, have gradually become one of the development trends of synthetic organic chemistry. In this work we synthesize a series of N-heterocyclic compounds based on Hantzsch reaction and 1,3-dipolar cycloaddition reaction.Preparation of a series of new 1H-indol-3-yl pyridine derivatives by the one-pot Hanztsch reactions coupling of aromatic aldehydes, aromatic ketones, 3-cyanoacetylindoles and ammonium acetate is studied under microwave irradiation. However, in the heating conditions, the main products were dihydropyridine compounds, showing that the microwave irradiation can effectively promote the aromatization of dihydropyridine to pyridine. This synthetic method has the broad substrate scope, even with substituents on the aromatic aldehydes, aromatic ketones, cyanoacetylindole derivatives, can be successfully obtained a series of new pyridine heterocycles. In addition, to extend the substrate scope and rich multi-functional pyridine derivatives library, three-component reaction of 1-methyl-2-cyanoacetyl pyrrole, 1,3-diarylpropenone and ammonium acetate was reported.Condensation reaction of 1-methyl-2-cyanoacetylpyrrole with aromatic aldehydes afforded 3-aryl-2-cyano-1-(1-methylpyrrole-2-yl)-1-propenone as dipolarphiles. A series of novel spiropyrrolidine derivatives were successfully synthesized via a three-component 1,3-dipolar cycloaddition reaction of azomethine ylide which generated in situ from sarcosine and isatin and 3-aryl-2-cyano-1-(1-methylpyrrole-2-yl)-1-propenones in refluxing methanol. All these compounds were obtained in yield of 70 %-89 %. The structures of all new compounds obtained were confirmed by 1H NMR, IR and elementary analysis. The stereo conformation of spiroheterocyclic compounds was achieved by X-ray single crystal analyses. The regioselectivity and steroselectivity of the reaction were discussed. On this basis, in order to enhance the efficiency of multi-component reactions and change the traditional synthetic strategy of 1,3-dipolar cycloaddition reaction, four-component 1,3-dipolar cycloaddition reaction of 1-methyl-2-cyanoacetylpyrrole, isatin(acenaphthequinone), sarcosine and aromatic aldehydes was reported. Comparison between the microwave-assisted and the conventional refluxing has been made,revealing that the microwave-assisted protocol can significantly shorten the reaction time. The current process provides a simple and efficient method to obtain a variety of novel spiropyrrolidine.Finally, a series of triphenylamine-pyridine derivatives were designed and synthesized through multicomponent reaction. These compounds were examined by UV-vis and fluorescence emission spectrum. Cyclic voltammetry illustrated that the materials had low HOMO energy levels. The compounds had not glass transition temperature due to the great polarity of molecules. Because of hole-transporting properties triphenylamine, indole group and electron-transporting properties pyridine, cyano group in molecule, these compounds can be applied as good multifunction dopant emitter in Organic Light-emmitting Devices (OLEDs).