REACTIVITIES OF SOME ALLYLIC HYDROPEROXIDES TOWARD ALLYLIC REARRANGEMENT AND RELATED REACTIONS

The allylic rearrangement has been studied of the hydroperoxides that are formed when singlet oxygen reacts with epicholesterol A9, 10-octahydronaphthalene, 2, 3-dimethylbut-2-ene, cyclopentylidenecyclopentane, and cy-clohexylidenecyclohexane. The reactivity in this sense decreases in the above sequence. l-(Cyclopent-l-enyl)cyclopentyl hydroperoxide rearranges only slowly, but in the presence of triplet oxygen it reacts to give l-(5-hydroperoxycyclopent-l-enyl)cyclopentyl hydroperoxide, and l-(cyclohex-l-enyl)cyclohexyl hydroperoxide does not rearrange and shows only the reaction with oxygen to give l-(6-hydroperoxycyclohex-l-enyl)cyclohexyl hydroperoxide. The various factors that affect the rates of these reactions are discussed. It is suggested that the reactivity and regioselectivity in the autoxidation which leads to the formation of dihydroperoxides implies that the reaction involves not the usual two-step propagation sequence, but a three-step sequence in which the chain carriers are a cycloalkenyl radical, a cycloalkenylperoxyl radical, and a cycloalkylperoxyl radical. © 1990, American Chemical Society. All rights reserved.