1H and 13C Nuclear Magnetic Resonance Reinvestigation of the Dibenzocyclononatetraenyl Anion and Its 5,9-Diphenyl Derivative. Planarity vs Nonplanarity

Article abstract of DOI:10.1021/jo00262a038

It is found that the dibenzocyclononatetraenyl anion is readily transformed into the stable 1H-cyclopentaphenanthren-1-yl anion.Earlier reported NMR data of this compound were incorrectly assigned to a planar structure of the dibenzocyclononatetraenyl anion.The nonplanarity of the initially formed nine-membered ring anion was confirmed both experimentally and theoretically.The ring-closure process does not take place in the anion of the 5,9-diphenyl derivative, which retains a nonplanar conformation of the nine-membered ring.