Oxidation of a triple carbo[5]helicene with hypervalent iodine

Abstract

The reactivities of both diastereomers of hexabenzotriphenylene (HBTP), a triple carbo[5]helicene of the formula C₄₂H₂₄, were examined in the presence of phenyliodine diacetate (PIDA) as an oxidizing agent. The D₃-symmetric diastereomer afforded two different ring rearranged ketone-containing products embedding a spirofluorene moiety. In contrast, under similar conditions, the C₂-symmetric diastereomer afforded predominantly a cyclodehydrogenation product. Altogether, this shows that stereochemistry is a critical factor in the reactivity of non-planar polycyclic aromatic hydrocarbons.