Photochemical Cyclization of o-Methylphenyl 1,3-Diketones

Article abstract of DOI:10.1021/jo00259a001

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 γ-hydrogen abstraction followed by interception of the resulting 1,4-biradical by the second carbonyl group is proposed.