Novel chiral norbornadiene-quadricyclane systems: Substituent effect on chiroptical properties and stereochemical consequence of photochemical interconversion

Hideo Nishino, Asao Nakamura, Mariko Terada, Atsuko Kosaka, Mieko Fukui, Noriko Aoki, Yoshihisa Inoue

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

For efficient absolute asymmetric synthesis (AAS) by circularly polarized light (CPL), a series of 3-substituted 2-methoxycarbonylnorbornadiene (N) and -quadricyclane (Q) derivatives (R = H, Me, Ph, 4-biphenylyl, 1- and 2-naphthyl) were prepared and optically resolved, and the chiroptical properties of the enantiomeric pairs were determined in hexane and acetonitrile. All of the N and Q derivatives gave moderate to large circular dichroism intensities (Δε) and specific rotations ([α]D). In particular, aromatic Ns (R = 4-biphenylyl and 2-naphthyl) gave high [α]D values of 216° and 206°, while non-aromatic Qs (R = H and Me) afforded high [α]D's of 322° and 271°. Depending on the nature of the substituent introduced at the 3-position, the maximum anisotropy factor (g = Δε/ε) varied over a wide range from 0.0141 (R = H) to 0.0022 (R = 1-naphthyl) in the N series and from 0.0091 (R = Me) to 0.0012 for (R = 2-naphthyl) in the Q series. Thus, non-aromatic N/Q pair is absolutely advantageous for the CPL-induced AAS reactions. The relatively high gmax values observed for non-aromatic Ns and Qs may be rationalized by the contribution of the n, π* transition of the ester chromophore to the N and Q chromophores. Stereochemical consequence of the photochemical interconversion of the chiral N and Q was also revealed; all of the (-)-Ns examined photoisomerized to the corresponding (+)-Qs without any side reactions.

Original languageEnglish
Pages (from-to)1-14
Number of pages14
JournalJournal of Photochemistry and Photobiology A: Chemistry
Volume147
Issue number1
DOIs
Publication statusPublished - 2002 Feb 28
Externally publishedYes

Keywords

  • Absolute asymmetric synthesis
  • Anisotropy factor
  • Chiroptical property
  • Circular dichroism
  • Norbornadiene
  • Quadricyclane
  • Specific rotation

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Physics and Astronomy(all)

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