Synthesis of Chrysenes through an Unexpected Skeletal Rearrangement

Significance

In the development of a method for the synthesis of [4]helicenes (J. Ichikawa et al. Angew. Chem. Int. Ed. 2008, 47, 4870), the authors discovered that they could obtain halogenated chrysene as a major product by extending the reaction time. The authors also show that further modification of chrysenes 3a-e is possible at the halogenated positions through lithiation-protonation to give the nonhalogenated derivatives and cross-coupling. The single crystals π-stack in one of three motifs shown above, while the non­halogenated analogue assumes a herringbone conformation.