Synthesis of methylene-bridged polyarenes

Article abstract of DOI:10.1016/S0040-4020(01)92265-3

Methylene-bridged polyarenes are a relatively rare class of polycyclic aromatic hydrocarbons whose chemistry is relatively unexplored. Although they are suspected carcinogenic environmental pollutants, few hydrocarbons of this class are known, and general synthetic approaches are lacking. Convenient syntheses of a series of methylene-bridged polyarenes are now described. These syntheses are based upon the prototype hydrocarbon cyclopenta[def]phenanthrene (1) which contains a pre-existing methylene bridge. Polyarenes prepared include 13H-dibenz[bc,l)aceanthrylene (3), 4H-cyclopenta[pqr]picene (5), 4H-benzo[b]cyclopenta[mno]chrysene (6), 13H-indeno[2,1,7-qra]naphthacene(7), and 4H-cyclopenta[def]dibenz[a,c]anthracene (8), all of which were previously unknown. Attempts to prepare 4H-benzo[c]cyclopenta[mno]chrysene (4) by catalytic or chemical dehydrogenation of its hexahydro precursor failed. This is likely due to steric crowding in the fjord region of 4 coupled with resistance to deformation from planarity caused by the methylene bridge. Preliminary findings from mutagenesis assays support the hypothesis that the active mutagenic metabolites of methylene-bridged polyarenes are sulfate esters of alcohol metabolites in the bridge sites.