Mieusset Jean-Luc, Brinker Udo H
Institut für Organische Chemie, Universität Wien, Währinger Strasse 38, A-1090 Wien, Austria.
J Am Chem Soc. 2006 Dec 13;128(49):15843-50. doi: 10.1021/ja065595y.
B3LYP/6-311+G(d,p) computations of the stabilization energies, singlet-triplet energy gaps, and lowest transition states for a set of cyclic alkenylidenes were performed in order to find the strongest interactions between the C-C double bond and the carbene center. The results suggest that among the alkenylidenes investigated in this study, those with a norbornenylidene structure represent strongly stabilized carbenes with a reduced reactivity toward intermolecular reactions. Further stabilization is found when the double bond is electron-rich or pyramidalized. Thus, for the rearrangement of syn-34 to take place, an activation barrier of about 22 kcal/mol needs to be overcome. The inclination to undergo a retro-Skattebøl rearrangement, which to our knowledge has never been observed experimentally, is characteristic for highly stabilized foiled carbenes.
为了找到碳 - 碳双键与卡宾中心之间最强的相互作用，对一组环状亚烯基的稳定化能、单重态 - 三重态能隙和最低过渡态进行了B3LYP/6 - 311 + G(d,p)计算。结果表明，在本研究中所研究的亚烯基中，具有降冰片烯亚基结构的那些代表了具有强烈稳定化作用的卡宾，其对分子间反应的反应性降低。当双键富含电子或呈金字塔形时，会发现进一步的稳定化。因此，对于顺式 - 34的重排发生，需要克服约22千卡/摩尔的活化能垒。据我们所知，经历逆 - 斯卡泰博尔重排的倾向从未在实验中观察到，这是高度稳定的受阻卡宾的特征。
