Norbornanes. Part 21. Bridging strain in norbornyl and oxanorbornyl cations
作者:Peter Flury、Cyril A. Grob、Guang Yi Wang、Hans-Werner Lennartz、Wolfgang R. Roth
DOI:10.1002/hlca.19880710512
日期:1988.8.10
Further evidence is presented that the 2-norbornyl 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 bicyclo[3. 2. 0. 0.2,7]heptane 18 indicates that the strain energy of the latter is ca. 21.5 kcal/mol higher that that of 17. Furthermore, 6-exo-2-oxabicyclo[2. 2. 1]heptyl
进一步的证据表明,2-降冰片基阳离子主要通过C(2)–C(6)桥接而稳定,而C(2)–C(7)桥接导致抑制性应变。因此,比较了三环戊二烯17和双环的氢化热[3。2. 0. 0. 2.7 ]庚烷18指示后者的应变能是大约21.5更高千卡/摩尔的是那个的17。此外,6 - exo -2--2-氧杂双环[2。2. 1]庚基磺酸盐8与强O(2)参与电离,生成桥连的氧鎓离子12。相反,2-内-7氧杂双环[2.2.1]庚基磺酸盐11在没有O(7)参与的情况下电离,形成未桥连的碳正离子15。