Photochemically generated bicyclic ortho-quinodimethanes: Photo- enolization of bicyclic aldehydes and ketones

Article abstract of DOI:10.1016/S0040-4020(97)10068-0

A photoenolization route to bicyclic ortho-quinodimethanes was investigated. Bicyclic photoenols were trapped in an intermolecular fashion with various dienophiles for the first time. All ortho-quinodimethane precursors were prepared via a selective route commencing with 1-indanol, α- tetralol and 1-benzosuberone. Irradiation afforded the E-photoenols exclusively which were trapped with equal efficiency except that derived from indane-4-carboxaldehyde. This low efficiency has been ascribed to rapid auto- oxidation of the aldehyde to carboxylic acid. The facial selectivity of the reaction between the photoenol from benzosuberan-9-carboxaldehyde and dimethyl fumarate was much lower when compared to the other aldehydes in this study. A distorted diene caused by the presence of the seven membered ring explains these results.