Photoinduced Electron-Transfer Reactions of Polyenes and Small Ring Compounds

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The photoinduced CR Cope rearrangements of 2,5-diaryl-1,5-hexadiene derivatives were investigated in terms of the energy surface. Combining chemical evidences with results on Ea for cyclization of diene cation radicals and the energy level of the cyclohexa-1,4-cation radical ion-pair obtained by pulse-radiolysis and photoacoustic calorimetric analysis, a cation radical cyclization-diradical cleavage mechanism was established for the photoinduced CR Cope rearrangement. The PET reaction of 1,4-diaryl-2,3-dimethylbicyclo[2.2.0]hexanes which is related to the CR Cope rearrangement provided the sensitizer and solvent polarity-dependent dual reactivity of 1,4-diaryl-2,3-dimethylbicyclo[2.2.0]hexane cation radicals. The intramolecular [2+2]cycloadditions of 2,6-diaryl-1,6-heptadiene cation radicals to form bicyclo[3.2.0]hexanes occurred efficiently, but the efficiency markedly decreased with an increase in the number of the methylene group between two stirene units for the PET reactions of 2, … More 7-diaryl-1,7-octadienes and 2,8-diaryl-1,8-nonadienes.The PET reactions of the 3,4-bis(styryl)-substituted furan and pyrrole derivatives were investigated by laser flash photolysis, which proved the generation of fused dimethylenefuran and dimethylenepyrrole derivatives and provided rate constants of chemical capture with electron-deficient diylophiles. By combination of these results with stereochemistry of chemical capture and MO calcultations, the ground state singlet states of fused dimethylenefuran and dimethylenepyrrole derivatives was determined. Experimental verification of the inversion of the spin multiplicity of dimethylenepyrroles is currently investigated for pyrrole derivatives with an electron-withdrawing group.Photoexciation reactions of solid state molecular complexes of BTDA and three divinyl benzenes provided intersting [2+2]cycloaddition reactions via electron-transfer. The probable absolute asymmetric synthesis via the single crystal-to-single crystal transformation is currently investigated for the solid state PET reaction of the molecular complex of BTDA and omicron-divinylbenzene. Less