PHOTOOXYGENATION REACTIONS OF 4-FLAVANOLS AND BENZYLIC-TYPE ALCOHOLS.

Article abstract of DOI:10.1246/bcsj.57.1870

On irradiation in benzene under oxygen atmosphere cis- and trans-4-flavanols gave flavanones with significant structural effects on the yield: A high cis/trans selectivity and enhancement effect by electron-donating substituents. A series of benzylic-type alcohols showed similar substituent effects. The structure-reactivity relationships were explained in terms of the stereoelectronic requirements for favorable overlapping of intermediates. In order to infer the active oxidant species, the photoreactions were compared with the oxidations by singlet oxygen and superoxide ion. The involvement of superoxide ion or its related species such as electron transfer complex R** plus **. . . . O//2** minus **. was suggested. The effects of additives and solvents were also investigated.