Abstract
Dibenzobarrelenes have been prepared by the cycloaddition of benzyne to anthracenes. The first method gives complex mixtures from which only poor yields of 1, 4-adducts may be obtained,1 exceot wgeb tetragakivebztbes are enokited,2,3 Muller and Vergne have reported4 that dibenzobarrelene is formed by the reaction of acetylene with anthracene, but it may be significant that later workers have chosen to use either the above-mentioned benzyne route or a modification of the cycloaddition to anthracenne involving dichlorethylene followed by dechlorination to prepare the parent compound.5 Our approach to the synthesis of this ring system employs our previously described 1,2–photoaramatisation reactions.6 A significant feature of the present work is that it demonstrates that a photochemical reaction can be employed to generate compounds, in this case dibenzobarrelenes, known to be photolabile.7