Conformations of Azacyclodeca-3,8-diynes and 1,6-Diazacyclodeca-3,8-diynes and the Generalized Anomeric Effect: A Test for Current Conformational Models for Azaheterocycles
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- 作者：Joachim Ritter ; Rolf Gleiter ; Hermann Irngartinger ; and Thomas Oeser
- 刊名：Journal of the American Chemical Society
- 出版年：1997
- 出版时间：November 5, 1997
- 年：1997
- 卷：119
- 期：44
- 页码：10599 - 10607
- 全文大小：214K
- 年卷期：v.119,no.44(November 5, 1997)
- ISSN：1520-5126
文摘
The conformations of azacyclodeca-3,8-diyne (4a) andits N-methyl (4b) and N-isopropyl(4c) derivativesas well as 1,6-diazacyclodeca-3,8-diyne (5a) and its1,6-dimethyl (5b), 1,6-diisopropyl (5c),1,6-di-tert-butyl (5d),and 1,6-ditolyl (5e) derivatives have been investigated bysingle-crystal X-ray diffraction, in solution by NMR andby theoretical methods. In the solid state, 4a,c and5a-e adopt a chair conformation with thesubstituents in thebis-axial positions. In solution 4 and 5show 
G
= 10.4 and 11.0 kcal/mol,respectively, for ring inversion. Trappingof 5c with HCl indicates the presence of bis-axial, axial,and equatorial conformations in solution. Theequilibriumbetween boat and chair conformations in 4 and 5is ascribed to much reduced torsional strain between thepropargylichydrogens. The preference of the axial orientation of thesubstituents on the nitrogen atom(s) in 4 and5 is interpretedin terms of the vicinal interactions of both the NR bond and thelone pair with the adjacent CH and CC bonds,synaxial 1,3-interactions of both the NR bond and the lonepair, and secondary interactions of CH/CC bonds ofthealkyl substituent with the endocyclic CH2 groups as well aswith triple bonds (back and frontstrain).
G = 10.4 and 11.0 kcal/mol,respectively, for ring inversion. Trappingof 5c with HCl indicates the presence of bis-axial, axial,and equatorial conformations in solution. Theequilibriumbetween boat and chair conformations in 4 and 5is ascribed to much reduced torsional strain between thepropargylichydrogens. The preference of the axial orientation of thesubstituents on the nitrogen atom(s) in 4 and5 is interpretedin terms of the vicinal interactions of both the NR bond and thelone pair with the adjacent CH and CC bonds,synaxial 1,3-interactions of both the NR bond and the lonepair, and secondary interactions of CH/CC bonds ofthealkyl substituent with the endocyclic CH2 groups as well aswith triple bonds (back and frontstrain).