1H-NMR Spectra of Cyclohexa-1,4-dienes and Cyclohexenes Annellated to Bicyclo[2.2.1]hept-2-enes. The Inter-Ring Homoallylic H,H Coupling Constants as Stereochemical Probes
作者:Cyril Mahaim、Pierre-Alain Carrupt、Pierre Vogel
DOI:10.1002/hlca.19850680814
日期:1985.12.18
cyclohexenes annellated to bicyclo[2.2.1]hept-2-enes and 7-oxabicyclo[2.2.1]hept-2-enes show inter-ring homoallylic coupling constants between the bridgehead protons of the bicyclo[2.2.1]heptenes and the exo-protons of the allylic methylene groups (0.8 ± 0.15 Hz for bicyclo[2.2.1]hept-2-enes; 0.8–1.4 Hz for 7-oxabicyclo[2.2.1]hept-2-enes). Contrastingly, the corresponding coupling between the bridgehead protons
与双环[2.2.1]庚-2-烯和7-氧杂双环[2.2.1]庚-2-烯成环的环己-1,4-二烯和环己烯的360-MHz- 1 H-NMR谱显示,双环[2.2.1]庚烯的桥头质子与烯丙基亚甲基的外质子之间的环均烯丙基偶合常数(双环[2.2.1]庚-2-烯为0.8±0.15 Hz;双环[2.2.1]庚-2-烯为0.8-1.4 Hz 7-氧杂双环[2.2.1]庚-2-烯)。与此相反,相应的桥头质子和之间的耦合内-质子不存在。将观察到的值与通过INDO和CNDO / 2方法计算得到的值进行比较,并根据双环[2.2.1]庚-2-烯键π各向异性进行讨论。孔内和环内均烯丙基偶联常数与环己-1,4-二烯环朝着内表面的小褶皱一致。烯丙基外-亚甲基质子比内-质子更脱屏蔽,而与取代基的性质,桥的性质和环化体系的不饱和度无关。这些结果构成了与这些双环骨架成环的环己-1,4-二烯和环己烯构型的探针。