Synthesis And Reaction Activity Of Cyclopentenyl Carbonium Salts

Carbocations are important organic reactive intermediates, whose formation, structure and stability have great significance in the chemical reaction mechanism clarification and reaction products prediction. Because of their quite instability, a considerable number of carbocations could only been prepared in strongly acidic media, and keep long-life at low temperature at present, which limited the application greatly. Since the stability of the compounds were closely linked with their own structure, it is of great possibility to change the molecular structure of the substrate to realize the stability regulation. This thesis centres on the synthesis and reaction activity research of polyarylcyclopentenyl derivatives. Several triarylcyclopentadiene substrates were designed and successfully synthesized.With the proton addition at room temperature, the cyclopentenyl carbocation compounds stable at environment temperature were synthesized. Their synthesis condition and structural stability were studied; The degradation reaction of cyclopentenyl carbenium resulted in two excellent photoelectric materials including naphthalene derivatives and perchlorate pyrylium salts in only one step.The main research contents are as follows:1. Synthesis and properties of triaryl substituted cyclopentadiene derivatives. In this part, four cyclopentadiene derivatives were successfully prepared. Their structure were characterized by NMR spectra, HRMS and single-crystal X-ray diffraction studies. The Uv-vis absorption and emission spectra in solution and aggregation state were studied. They shows solvent-dependent fluorescence and aggregation-induced emission enhancement (AIEE) characteristic when aggregated in water/acetonitrile mixture or in crystals. The crystal structure analysis reveals the relationship bewteen sructures and properties.2. Synthesis and stability property of cyclopentenyl carbenium. Carbocations durable at environment temperature were synthesized on the basis of oxidation of cyclopentadiene derivatives by HCIO4. Comparing the proton adduct of cyclopentadiene derivatives with different substituents, the electron-donor effect of-OMe and p-n conjugation function induced the synthesis and structure stability of cyclopentenyl salts; the effect of reaction conditions and temperature on the synthesis of cyclopentenyl carbenium were studied.3. The reaction activity of cyclopentenyl compounds and optical properties of their products. Naphthalene derivatives and perchlorate pyrylium salts were synthesized from cyclopentenyl carbenium in CH3CN and ethyl acetate, respectively, and were represented by high resolution mass spectrum,1H NMR spectra,13C NMR spectra and X-ray crystal analysis. Fluorescence spectra showed that these two compounds had a higher fluorescence quantum efficiency in aggregation state than in solution.