Skeletal Rearrangement of Twisted Polycyclic Aromatic\nHydrocarbons under Scholl Reaction Conditions

Abstract

Treatment\nof a twisted polycyclic aromatic hydrocarbon containing\ncyclooctatetraene fused by two 9,9′-bifluorenylidene units\nunder the Scholl reaction conditions (FeCl₃ or 2,3-dichloro-5,6-dicyano-1,4-benzoquinone\nand scandium trifluoromethanesulfonate) led to stepwise skeletal rearrangements\nto afford initially a hydrocarbon with a seven-membered ring and then\ntetrabenzo­[<i>a</i>,<i>d</i>,<i>j</i>,<i>m</i>]­coronene with all six-membered rings. The course\nof the rearrangement was interpreted in terms of the acid-catalyzed\nisomerization of 9,9′-bifluorenylidene into dibenzo­[<i>g</i>,<i>p</i>]­chrysene moieties on the basis of theoretical\ninvestigations.