159. Photochemische Reaktionen Zur Photochemie konjugierter δ-Keto-enone und β,γ,δ,ε-ungesaettigter Ketone

Article abstract of DOI:10.1002/hlca.19800630620

On ¹?,?*-excitation the δ-keto-enones 5-8 are isomerized to compounds B (18, 22, 26, 28) via 1,3-acyl shift and to compounds C (19, 23, 27, 29) via 1,2-acyl shift, whereas the β,γ,δ,ε-unsaturated ketone 9 gives the isomers 32 and 33 by 1,2- and 1,5-acyl shift, respectively.Furthermore, isomerization of 6 to 24, dimerization of 8 to 30 and addition of methanol to 8 (8->31) is observed.Unlike 7 and 8 the acyclic ketones 5, 6 and 9 undergo photodecarbonylation on ¹?,?*-excitation (5->20, 21; 6->20, 25; (E)-9->35-38).Evidence is given, that the conversion to B as well as the photodecarbonylation of 5, 6 and 9 arise from an excited singulet state, but the conversion to C as well as the dimerization of 8 from the T₁-state.