Phenacenes from Diels-Alder Trapping of Photogenerated o-Xylylenols

Significance

The synthesis of bisimide derivatives of the phenanthrene and benzo[e]pyrene ring systems is described. Enol intermediates, generated by photoisomerization of ortho-substituted aryl ketones, participate efficiently in Diels-Alder cycloadditions with maleimide derivatives to furnish the polycyclic backbone. Dehydration and dehydrogenation steps complete the synthesis of the target compounds, which are obtained in good yields (see scheme).