1H and 13C NMR study of the effects exerted by an oxirane ring in the epoxybicyclo-[2.2.2]octane series

✍ Scribed by H. Christol; C. Laffite; F. Plénat; G. Renard

• Publisher: John Wiley and Sons
• Year: 1981
• Tongue: English
• Weight: 681 KB
• Volume: 17
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1270170207

✦ Synopsis

Abstract

The ^1^H and ^13^C NMR spectra of 2,3‐disubstituted exo‐5,6‐ and endo‐5,6‐bicyclo[2.2.2]octanes, and the corresponding alkanes, have been investigated to determine the effects exerted by an oxirane ring. The ^1^H NMR study showed that the anti protons, H‐7__a__ and H‐8__a__, are significantly shielded and the syn protons, H‐7__s__ and H‐8__s__, are deshielded, although to a smaller extent, by the exo‐oxirane. An endo‐oxirane has practically no effect on the same protons. The stereochemistry of epoxybicyclo[2.2.2]octanes is, thus, easily deduced from ^1^H NMR data. The ^13^C NMR study of the epoxy compounds provided an estimate of the value of α, β, γ syn and γ anti effects (to the epoxide oxygen) of an oxirane ring. In these rigid bicyclic molecules, of known geometry, the γ syn and the γ anti effects are of the same value, even though the dihedral angles are very different (0° and 120°).