Sensitized Photooxygenation of 9-Vinylphenanthrenes

Abstract
The sensitized photooxygenation of several 9-vinylphenanthrenes in carbon tetrachloride was investigated. In the cases of 9-vinyl- and 9-(β-substituted vinyl) phenanthrenes, the 1,4-cycloaddition of singlet oxygen to a conjugated system composed of the side chain and 9,10-double bond of the ring surpassed other oxidation modes, i.e., the “ene” reaction and 1,2-cycloaddition of singlet oxygen, to give the 1,2-dioxatriphenylene-type peroxides. On the other hand, the sensitized photooxygenation of 9-isopropenylphenanthrene gave a hydroperoxide due to the “ene” reaction.