INFLUENCE OF THE BETA-SUBSTITUTION ON THE PHOTOCHEMISTRY OF ALPHA,2-DIACETOXYSTYRENES - IRRADIATION OF PHENYL, VINYL, AND BENZYL DERIVATIVES

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 esters 4a-c; however other processes are also observed, depending on the substrate. The phenyl derivative 4a gives the E isomer 7a and the phenanthrene 9. The vinyl derivative 4b also undergoes cis-trans isomerization and/or photooxidation, to afford 7b and 10. Finally, a 1,4-acyl migration occurs in the benzyl derivative 4c, whereby the 1,4-diketone 12 is formed. © 1990 Springer-Verlag.