103. Photochemical Reactions. Photo-oxygenation of (E)- and (Z)-7-Methyl-β-ionone

Article abstract of DOI:10.1002/hlca.19890720510

Photo-oxygenation of (E)-7-methyl-β-ionone ((E)-1) and (E)-8-methyl-β-ionone ((E)-2) gave rise to the formation of the hydroperoxy-enones (E)-10 and (E)-15, respectively, which, in part, underwent intramolecular epoxidation to the hydroxy-epoxy-ketones 11 and 16, respectively.The product distribution of the photo-oxidation of (Z)-1 shows a marked influence of the skewed ground-state conformation of the dienone chromophore.Thus, singlet oxygen (¹O2) was added to C(γ) of the dienone chromophore leading to the spirocyclic peroxy-hemiacetal 12 and to the endoperoxide 13.In addition, the tricyclic peroxide 14 was formed as a new type of product via primary addition of ¹O2 to C(γ) of the dienone chromophore.The structure of 14 was established by X-ray crystal-structure analysis of the hemiacetal 22.