Investigation of the role of stereoelectronic effects in the conformation of piperidones by NMR spectroscopy and X-ray diffraction
| Autor: | Cesar Garcias-Morales, Armando Ariza-Castolo, David Ortegón-Reyna |
|---|---|
| Rok vydání: | 2015 |
| Předmět: |
stereoelectronic effect
Stereochemistry Chemistry Organic Chemistry Stereoelectronic effect Nuclear magnetic resonance spectroscopy Antibonding molecular orbital X-ray diffraction structure Full Research Paper lcsh:QD241-441 Crystallography NMR spectroscopy Molecular geometry lcsh:Organic chemistry Intramolecular force piperidone Proton NMR lcsh:Q Density functional theory lcsh:Science spin–spin coupling constant Natural bond orbital |
| Zdroj: | Beilstein Journal of Organic Chemistry, Vol 11, Iss 1, Pp 1973-1984 (2015) Beilstein Journal of Organic Chemistry |
| ISSN: | 1860-5397 |
| Popis: | This paper reports the synthesis of a series of piperidones 1–8 by the Mannich reaction and analysis of their structures and conformations in solution by NMR and mass spectrometry. The six-membered rings in 2,4,6,8-tetraphenyl-3,7-diazabicyclo[3.3.1]nonan-9-ones, compounds 1 and 2, adopt a chair–boat conformation, while those in 2,4-diphenyl-3-azabicyclo[3.3.1]nonan-9-ones, compounds 3–8, adopt a chair–chair conformation because of stereoelectronic effects. These stereoelectronic effects were analyzed by the 1JC–H coupling constants, which were measured in the 13C satellites of the 1H NMR spectra obtained with the hetero-dqf pulse sequence. In the solid state, these stereoelectronic effects were investigated by measurement of X-ray diffraction data, the molecular geometry (torsional bond angles and bond distances), and inter- and intramolecular interactions, and by natural bond orbital analysis, which was performed using density functional theory at the ωB97XD/6311++G(d,p) level. We found that one of the main factors influencing the conformational stability of 3–8 is the interaction between the lone-pair electrons of nitrogen and the antibonding sigma orbital of C(7)–Heq (nN→σ*C–H(7)eq), a type of hyperconjugative interaction. |
| Databáze: | OpenAIRE |
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