Synthesis and Chiroptical Properties of Binaphthyl‐Hinged [5]Helicenes

Abstract The synthesis, structure, and circularly polarized luminescence (CPL) of two types of shape‐persistent [5]helicenes, hinged by a tethered (−OCH 2 CH 2 O−) or untethered (−OCH 3 ) binaphthyl, are reported. The binaphthyl tethering system facilitated an effective Wittig ring‐closure reaction in the synthesis of a macrocyclic precursor, which could be easily converted to the title compound via successive photocyclization. The tethered groups were replaced with untethered −OCH 3 groups by treatment with BBr 3 followed by methylation. Both compounds exhibited similar spectra, and their longest wavelength absorption band with a low intensity was attributed to the transition from HOMO to LUMO+1. These compounds exhibited CPL with higher dissymmetry factors g lum values than unlocked helicenes.