Studies On Several Photochemical Rearrangement Reactions Of Aromatic Compounds

Organic photochemical reaction (OPR) focuses on the conversion frommolecule(s) to other molecule(s) induced by light, which shows many advantages,such as simple operation and post-processing, almost no waste is generated, littleside-products, et al. Photochemical rearrangement reaction is an important OPR dueto its application for the preparation of highly functionalized compounds whichwould be difficult to access with standard chemical reactions in the ground state andtotal synthesis of natural products. In the thesis, cinnamate esters and aromaticγ,δ-epoxy ketones were selected as the research objects, the photochemistry of themwas studied in solution under variable conditions.The photochemistry of cinnamate esters was studied using500Whigh-pressure mercury lamp as light resource in different solution at roomtemperature. It’s found that cinnamate esters could be conversed to polysubstitutedisochromanone derivatives via a novel photochemical rearrangement reaction. Theinfluence of solvents, time of irradiation on this reaction was studied by GC basedon the conversation of substrate and yield of photoproduct, the results showed thatthe highest yield of isochromanone was89.6%when the experiment was advancedin degassed anhydrous benzene with500W high-pressure mercury lamp as lightresource. After studies on the proposed mechanism of this novel photochemicalrearrangement reaction, the application of it to aromatic α,β-unsaturated ketone andpreparation of isochromanone derivatives were discussed preliminarily. At last, thephotoinduced asymmetric synthesis of isochromanone was studied in solution.The preparation of aromatic γ,δ-epoxy ketones and photochemistry of themwas studied in solution and a novel photorearrangement reaction was found, namedNorrish type-Ⅱ/semi-pinacol rearrangement tandem reaction. After theoptimization of conditions, it can be concluded that the yield photoproductbenzocyclobutanone was highest with anhydrous degassed benzene solution assolvent and450W medium-pressure mercury lamp as light source. Additionally, thephotorearrangement reaction couldn’t be happened if the γ-H or δ-H of ketonecarbonyl was substituted with methyl. At last, the proposed mechanism andapplication of it in organic synthesis were discussed simply.The photochemistry of aromatic γ,δ-epoxy ketones with substituted epoxygroup was studied in solution using450W medium-presure mercury lamp as lightsource. The results revealed that these substrates could be conversed tobenzocyclopentenones by a novel photoinduced epoxy rearrangement/1,5-biradicalscyclization tandem reaction. The result of analysis of solvent, wavelengths and lewis acid on this photorearrangement reaction showed anhydrous degassedbenzene was the best solvent, the yield of benzocyclopentenone could be higherthan80.0%under the optimized condition. The proposed methanism of thisreaction and the potential application of this new photochemical rearrangementreaction to synthesis of benzocyclopentenone were studied be analysis theabsolutely structure of the photoproduct.