Cross-conjugated oligothiophenes derived from the (C2S)n helix: asymmetric synthesis and structure of carbon-sulfur [11]helicene

J Am Chem Soc. 2005 Oct 12;127(40):13806-7. doi: 10.1021/ja055414c.

Abstract

(-)-Sparteine-mediated asymmetric synthesis of di-n-octyl-substituted carbon-sulfur [11]helicene, a helical (C2S)n beta-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 (-)-[11]helicene, respectively. X-ray structures for homologous [11] and [7]helicenes indicate similar helical curvatures. The optical band gap, Eg approximately 3.5 eV, is estimated for the (C2S)n helix polymer, with onset of electron localization at n </= 7.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Carbon / chemistry*
  • Crystallography, X-Ray
  • Magnetic Resonance Spectroscopy / methods
  • Magnetic Resonance Spectroscopy / standards
  • Models, Molecular
  • Molecular Structure
  • Polycyclic Compounds* / chemical synthesis
  • Polycyclic Compounds* / chemistry
  • Reference Standards
  • Sulfur / chemistry*
  • Thiophenes / chemical synthesis*
  • Thiophenes / chemistry

Substances

  • Polycyclic Compounds
  • Thiophenes
  • beta-heptathiophene
  • beta-undecathiophene
  • helicenes
  • Sulfur
  • Carbon