The photochemistry of five 1,3-dicarbonyl compounds, substituted at the 1-position with an o-methylphenyl group, has been investigated. Compounds 5a-c cyclize upon irradiation to give tetralones 6a and 6c and octahydroanthracene derivative 6b, respectively. Compounds 5d and 5e do not form similar photoproducts. Diketone 5c is the most efficient in this reaction, indicating that the reaction probably occurs via the keto tautomer. A mechanism involving initial y-hydrogen abstraction followed by interception of the resulting 1,Cbiradical by the second carbonyl group is proposed.

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Bei der Photolyse der Isochromene (I) erhält man über die Dimethylenverbindungen (II) unter Umlagerung die ungesättigten Ketene (III), die in Gegenwart von Methanol die Ester (IV) ergeben, während die weitere Photolyse in Benzol unter Decarbonylierung über (V) zum o‐Methylstyrol (VI) führt.