COMPUTATIONAL STUDIES OF DECOMPOSITION REACTIONS OF 1,4-DIPHENYL-2,3-DIOXABICYCLO2.2.2OCTANE RADICAL CATION GENERATED BY PHOTOINDUCED ELECTRON TRANSFER

摘要

2,4,6-Triphenylpyrylium tetrafluoroborate sensitized reactions of 1,4-diary-2,3-dioxabicyclo[2.2.2]octanes in the presence of 2,6-di-tert-pyridine in dichloromethane afforded 1,4-diarylbutan-1,4-diones in good yields. Photolyses under the various conditions along with fluorescence quenching experiments indicated that the reactions proceed through the radical cations of the bicyclic peroxides with elimination of emylene molecule. Semi-empirical molecular orbital calculations (PM3) have shown that 1,4-diphenyl-2,3-dioxabicyclo[2.2.2]octane radical cation undergoes rather stepwise C-C bond fissions of two carbon-carbon bonds between the ethylenic and benzylic carbons to afford the neutral ethylene and 1,4-diphenyl-1,4-diketone radical cation.