Synthesis of a series of novel polycyclic aromatic systems: isomers of benz[a]anthracene containing a cyclopenta-fused ring

The four possible isomers of benz(a)anthracene containing a cyclopenta-fused ring have been synthesized and characterized. These systems are of interest for structure-activity studies in bioactivation because of their predicted high level of activity. Formation of fused five-membered rings by intramolecular cyclodehydration, often difficult to accomplish, was found to be smoothly effected in anhydrous hydrofluoric acid (HF), provided the reactivity index (N/sub t/a) for the appropriate electrophilic addition was favorable. The dihydro polycyclic aromatic alcohols obtained from reduction of the corresponding keto cyclodehydration products were best dehydrated to the desired polycyclic aromatic hydrocarbons (PAH) by activity grade I neutral alumina in refluxing benzene. This dehydration proceeds in high yield without the formation of isomeric or polymeric side products that occurred even under such mild acid catalysis as p-toluenesulfonic acid.