New SYNTHETIC METHOD OF 13H-DIBENZO[A,DE]ANTHRACENE-13-ONE

The polycyclic aromatic ketone, 13H-dibenzo[a,de]anthracene-13-one (5,6-BBz) is useful as a starting material for synthesis of undecacyclic aromatic compounds by means of condensation. To synthesize 5,6-BBz, glycerol condensation of benzo[a]anthraquinone was conducted. The condensation, however, gave two structural isomers besides 5,6-BBz and the isolation was very difficult; separation of the crude products by column chromatography or high-vacuum sublimation was unsuccessful because of their similarity in structure and vapor pressure. Only a little 5,6-BBz was obtained by repeated recrystallization, but the amount was insufficient for condensation. Thus, we developed a new synthetic method which affords 5,6-BBz selectively. 9-(o-Chlorobenzoyl)anthracene was synthesized by the Friedel-Crafts' reaction of anthracene with o-chlorobenzoyl chloride and aluminum chloride anhydride. In order to suppress the production of 9,10-di(o-chlorobenzoyl) anthracene, the reaction was performed at low temperature. The crude products obtained were purified by column chromatography on activated alumina and then recrystallized with benzene, which yielded yellow crystals of 9-(o-chlorobenzoyl)anthracene. The structure of 9-(o-chlorobenzoyl)anthracene was determined by X-ray diffraction analysis for the first time. Cyclo-dehydrohalogenation of 9-(o-chlorobenzoyl) anthracene gave 5,6-BBz selectively, the amount of which was sufficient for synthesizing undecacyclic aromatic hydrocarbons.