Summary
β-Substitution shows a pronounced influence on the photochemistry of α,2-diacetoxystyrenes. As in the case of the parent compound, intramolecular cyclization with participation of the neighbouring 2-acetoxy group takes place upon irradiation of the enol esters4a–c; however other processes are also observed, depending on the substrate. The phenyl derivative4a gives theE isomer7a and the phenanthrene9. The vinyl derivative4b also undergoescis-trans isomerization and/or photooxidation, to afford7b and10. Finally, a 1,4-acyl migration occurs in the benzyl derivative4c, whereby the 1,4-diketone12 is formed.
Zusammenfassung
Bei α,2-Diacetoxystyrolen haben die β-Substituenten einen deutlichen Einfluß auf das photochemische Verhalten. Wie im Fall der Stammverbindung erfolgt bei der Bestrahlung der Enolester4a–c intramoleukulare Cyclisierung unter Einbeziehung der benachbarten 2-Acetoxygruppe; jedoch werden je nach Substrat auch andere Reaktionen beobachtet. Das Phenylderivat4a liefert dasE-Isomer7a und das Phenanthren9. Das Vinylderivat4b erfährt ebenfallscis/trans-Isomerisierung zu7b und/oder Photooxidation zu10. Beim Benzylderivat4c tritt eine 1,4-Acylverschiebung zum 1,4-Diketon12 auf.
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Alvaro, M., Baldovi, V., Garcia, H. et al. Influence of the β-substitution on the photochemistry of α,2-diacetoxystyrenes. Irradiation of phenyl, vinyl, and benzyl derivatives. Monatsh Chem 121, 267–274 (1990). https://doi.org/10.1007/BF00808927
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DOI: https://doi.org/10.1007/BF00808927