Norbornanes. Part 21. Bridging strain in norbornyl and oxanorbornyl cations

✍ Scribed by Peter Flury; Cyril A. Grob; Guang Yi Wang; Hans-Werner Lennartz; Wolfgang R. Roth

• Publisher: John Wiley and Sons
• Year: 1988
• Tongue: German
• Weight: 498 KB
• Volume: 71
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19880710512

✦ Synopsis

Further evidence is presented that the 2-norbomyl cation is stabilized primarily by C(2)-C{6) bridging, and that C(2)-C(7) bridging leads to prohibitive strain. Thus, a comparison of the heats of hydrogenation of nortricyclene 17 and bicycl0[3.2.0.0~.~]heptane 18 indicates that the strain energy of the latter is ca. 21.5 kcal/mol higher than that of 17. Furthermore, 6-exo-2-oxabicyclo[2.2. ljheptyl sulfonates 8 ionize with strong O(2) participation to the bridged oxonium ion 12. In contrast, 2-endo-7-oxabicyclo[2.2.1]heptyl sulfonates 11 ionize without O(7) participation to form the unbridged carbenium ion 15. ') 2, 3, The IUPAC name for norbornane: 8,9,1U-trinorbornane. The rate ratio at 25"is 350 in AcOH [3], 580 in 80% EtOH [lb], and cn. 2000 in H2O [4].

For a definition of u participation, see .