School of Chemistry and Bio-21 Institute, University of Melbourne, Parkville, Victoria 3010, Australia.
J Org Chem. 2013 Jan 18;78(2):311-9. doi: 10.1021/jo3020243. Epub 2012 Dec 20.
σ(C-C)-σ*(C-O) interactions involving the strained carbon-carbon bonds of α- and β-nopinol, and their ester and ether derivatives have been demonstrated in the solid state using the variable oxygen probe. These hyperconjugative interactions are manifested as a strong response of the C-OR bond distance to the electron demand of the OR substituent. Although the effects upon the donor C-C bond distances are not large enough to be measurable by X-ray crystallography, they do result in systematic and measurable effects on the (13)C-(13)C one-bond coupling constants. For the donor C-C bond, coupling constants decrease, consistent with weakening of this bond, while the intervening C-C bond coupling constants increase, consistent with bond strengthening, as the electron demand of OR increases.
利用可变氧探针，在固态中证明了涉及α-和β-降诺匹醇的应变碳-碳键以及它们的酯和醚衍生物的 σ(C-C)-σ*(C-O) 相互作用。这些超共轭相互作用表现为 C-OR 键距离对 OR 取代基电子需求的强烈响应。尽管这些相互作用对供体 C-C 键距离的影响不足以通过 X 射线晶体学测量，但它们确实对（13）C-(13)C 单键耦合常数产生了系统且可测量的影响。对于供体 C-C 键，耦合常数减小，与该键的减弱一致，而中间的 C-C 键耦合常数增加，与键的增强一致，因为 OR 的电子需求增加。
