The C7H10 potential energy landscape:: Concerted transition states and diradical intermediates for the retro-Diels-Alder reaction and [1,3] sigmatropic shifts of norbornene

被引:88
作者
Beno, BR [1 ]
Wilsey, S [1 ]
Houk, KN [1 ]
机构
[1] Univ Calif Los Angeles, Dept Chem & Biochem, Los Angeles, CA 90095 USA
关键词
D O I
10.1021/ja9818250
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
The potential energy surfaces for the thermal reactions of bicyclo[3.2.0]hept-2-ene and norbornene have been explored with density functional theory at the Becke3LYP/6-31G* level. Both concerted and diradical pathways for the retro-Diels-Alder reaction of norbornene have been examined, and the activation parameters and C-13 primary kinetic isotope:effects predicted for the concerted pathway are in excellent agreement with experimental data. The concerted mechanism is favored over the lowest energy stepwise diradical route by 12.4 kcal/mol. For,the orbital symmetry-allowed suprafacial-inversion (si) pathway of the [1,3] sigmatropic rearrangement;of bicyclo[3.2.0]hept-2-ene to form norbornene, a mechanism involving a transition state which leads to a broad diradical plateau on the potential energy surface is predicted. Implications of these surfaces, which differ substantially from those obtained by semiempirical calculations, are also discussed.
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页码:4816 / 4826
页数:11
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