(-)-Sparteine-mediated asymmetric synthesis of di-n-octyl-substituted carbon-sulfur helicene, a helical (C2S)n β-undecathiophene, is described. The atom-efficient routes rely on one-step tri-annelation or two-step di- and mono-annelation to provide enantiomeric excess of (+)- or (-)-helicene, respectively. X-ray structures for homologous  and helicenes indicate similar helical curvatures. The optical band gap, Eg ≈ 3.5 eV, is estimated for the (C2S)n helix polymer, with onset of electron localization at n ≤ 7.
ASJC Scopus subject areas
- Colloid and Surface Chemistry