ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Photochemistry of γ,δ-Methano-α-enonesDirect excitation (λ = 254 or ≥ 347 nm) converts the γ,δ-methano-α-enone (E)-10 into the isomeric ether 23 and the isomeric diene-ketone 24. Furthermore, on 1π,π*-excitation (λ = 254 nm) (E)-10 undergoes an 1,3-homosigmatropic rearrangement yielding the enone (E)-25. In addition (E → Z)-isomerization of (E)-10 and conversion of 10 to the isomeric furan 28 is observed.The isomerization (E)-10 → 23, 24 and (E)-25 proceeds by photocleavage of the C(γ), C(δ)-bond, whereas the formation of 28 occurs by photocleavage the C(γ), C(δ)-bond together with that of the C(γ), C(δ′)-bond of 10.On direct excitation the bicyclic diene-ether 23 yields the methano-enone 10, the dieneketone 24 and the tricyclic ether 29. Evidence is given, that the conversion 23 → 10 is a singulet process. On the other hand, the isomerization 23 → 24 and the intramolecular [2 + 2]-photocycloaddition 23 → 29 are shown to be triplet reactions.Irradiation (λ = 254 nm) of the homoconjugated ketone 24 yields the isomeric ketone 27 by an 1,3-acyl shift. The excitation of the (E)-enone 25 induces (E → Z)-isomerization and photoenolization to give the homoconjugated ketone 26.
Additional Material:
1 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19800630621
