Helicenes Fused with Hexafluorocyclopentene (HFCP): Synthesis, Structure, and Properties

Helicenes fused with hexafluorocyclopentene (HFCP) were synthesized by oxidative photocyclization of stilbene derivatives (the Mallory reaction). Of the newly‐obtained fluorinated helicenes, the [7]helicenes bearing one‐ or three‐HFCP units were structurally characterized by X‐ray crystallographic analysis. The attempted synthesis of [9]helicene fused with three HFCP units resulted in the unexpected formation of a novel double helicene consisting of [4]‐ and [6]‐helicenes sharing peripheral benzene rings. Optical properties and chiral resolutions of the newly obtained HFCP‐substituted helicenes are also described. [7]Helicenes fused with 3,3,4,4,5,5‐hexafluorocyclopentene (HFCP) have been synthesized by using oxidative photocyclization of stilbene derivatives, i.e., Mallory reaction. A novel double helicene compound featuring [4]‐ and [6]‐helicene motifs connected by sharing a peripheral benzene ring was also obtained. Optical properties including chiroptical character (CD and CPL properties) are described.