التفاصيل البيبلوغرافية
| العنوان: |
Novel chiral norbornadiene–quadricyclane systems: substituent effect on chiroptical properties and stereochemical consequence of photochemical interconversion |
| المؤلفون: |
Nishino, Hideo1, Nakamura, Asao1, Terada, Mariko1, Kosaka, Atsuko1, Fukui, Mieko1, Aoki, Noriko1, Inoue, Yoshihisa nioue@chem.eng.osaka-u.ac.jp |
| المصدر: |
Journal of Photochemistry & Photobiology A: Chemistry. Feb2002, Vol. 147 Issue 1, p1. 14p. |
| مصطلحات موضوعية: |
*CHIRALITY, *ANISOTROPY, *CIRCULAR dichroism |
| مستخلص: |
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. [Copyright &y& Elsevier] |
| قاعدة البيانات: |
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