Towards configurationally stable [4]helicenes: Enantioselective synthesis of 12-substituted 7,8-dihydro[4]helicene quinones

M. Carmen Carreño, Alvaro Enríquez, Susana García-Cerrada, M. Jesús Sanz-Cuesta, Antonio Urbano, Feliu Maseras, Alfons Nonell-Canals

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Abstract

The synthesis of enantiopure C-12 methoxy- or alkyl-substituted 5,7,8,12b-tetrahydro[4]helicene quinones 16 and 17 and the 7,8-dihydroaromatic analogues 4 and 5 has been achieved from (SS)-2-(p-tolylsulfinyl)-1,4- benzoquinone. In the first series, with a structure containing both central and helical chiralities, the R absolute configuration of the stereogenic carbon atom was defined after the asymmetric cycloaddition step, whereas the P or M helicity was shown to be dependent on the nature of the C-12 substituent. The size of this group was also defining the configurational stability of the final (P)-7,8-dihydro[4]helicene quinones 4and 5. The interconversion barriers between the P and M helimers in the latter, computed with a DFT B3LYP method, matched well with the experimentally observed stability. Our study provided evidence that, in addition to steric effects, a small but significant role of electronic effects is governing the configurational stability of such helical quinones. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.
Original languageEnglish
Pages (from-to)603-620
JournalChemistry - A European Journal
Volume14
Issue number2
DOIs
Publication statusPublished - 22 Jan 2008

Keywords

  • Asymmetric synthesis
  • Cycloaddition
  • Helical structures
  • Quinones
  • Sulfoxides

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    Carreño, M. C., Enríquez, A., García-Cerrada, S., Sanz-Cuesta, M. J., Urbano, A., Maseras, F., & Nonell-Canals, A. (2008). Towards configurationally stable [4]helicenes: Enantioselective synthesis of 12-substituted 7,8-dihydro[4]helicene quinones. Chemistry - A European Journal, 14(2), 603-620. https://doi.org/10.1002/chem.200700762