α-Ketocarbenium Ions Derived from Orthoquinone-Containing Polycyclic Aromatic Compounds.

α-Ketocarbenium ions derived from synthesized orthoquinone-containing polycyclic aromatic compounds were generated in the presence of Brønsted acids such as sulfuric acid, trifluoromethanesulfonic acid, and fluorosulfonic acid. The prepared α-ketocarbenium ions were stabilized by conjugation of the aromatic moiety. In addition, unique absorption properties of the α-ketocarbenium ions were observed and identified on the basis of the calculated absorption spectra. It was suggested that the zigzag-shaped architecture stabilizes the newly discovered α-ketocarbenium ions derived from orthoquinone-containing polycyclic aromatic compounds.