Die Thermolyse von 2,2,6,7‐Tetramethyl‐1,7 ‐epidioxybicyclo[4.3.0]non‐8‐en

Thermolysis of 2,2,6,7‐Tetramethyl‐1,7‐epidioxybicyclo[4.3.0]non‐8‐ene. Dye‐sensitized photooxygenation of the cyclopentadiene derivative 1 gives three products: the peroxide 2a and the monocyclic ketones 5 and 8. 5 and 8 are probably formed by rearrangement of the unstable peroxide 2b. Thermolysis of 2a gives, besides 5 and 8, the furylketone 9 and the cyclooctenone derivative 10. The structures of the new compounds have been established by means of spectroscopic methods and chemical transformations. A reaction mechanism for the formation of 5, 8, 9 and 10 from 2a is proposed. Irradiation of 10 leads to the two diastereoisomeric trans cyclooctenones 12a and 12b.