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
Publication statusPublished - 2002 Feb 28
Externally publishedYes

Fingerprint

Light polarization
Chromophores
polarized light
chromophores
Derivatives
Dichroism
Hexanes
synthesis
Hexane
Acetonitrile
dichroism
acetonitrile
esters
Esters
Anisotropy
anisotropy
quadricyclane

Keywords

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

ASJC Scopus subject areas

  • Bioengineering
  • Physical and Theoretical Chemistry

Cite this

Novel chiral norbornadiene-quadricyclane systems : Substituent effect on chiroptical properties and stereochemical consequence of photochemical interconversion. / Nishino, Hideo; Nakamura, Asao; Terada, Mariko; Kosaka, Atsuko; Fukui, Mieko; Aoki, Noriko; Inoue, Yoshihisa.

In: Journal of Photochemistry and Photobiology A: Chemistry, Vol. 147, No. 1, 28.02.2002, p. 1-14.

Research output: Contribution to journalArticle

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T1 - Novel chiral norbornadiene-quadricyclane systems

T2 - Substituent effect on chiroptical properties and stereochemical consequence of photochemical interconversion

AU - Nishino, Hideo

AU - Nakamura, Asao

AU - Terada, Mariko

AU - Kosaka, Atsuko

AU - Fukui, Mieko

AU - Aoki, Noriko

AU - Inoue, Yoshihisa

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AB - 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.

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KW - Anisotropy factor

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KW - Circular dichroism

KW - Norbornadiene

KW - Quadricyclane

KW - Specific rotation

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