The C7H10 Potential Energy Landscape: Concerted Transition States and Diradical Intermediates for the Retro-Diels-Alder Reaction and [1,3] Sigmatropic Shifts of Norbornene

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• 作者：Brett R. Beno ; Sarah Wilsey ; and K. N. Houk
• 刊名：Journal of the American Chemical Society
• 出版年：1999
• 出版时间：May 26, 1999
• 年：1999
• 卷：121
• 期：20
• 页码：4816 - 4826
• 全文大小：216K
• 年卷期：v.121,no.20(May 26, 1999)
• ISSN：1520-5126

文摘

The potential energy surfaces for the thermal reactions of bicyclo[3.2.0]hept-2-ene and norbornenehave been explored with density functional theory at the Becke3LYP/6-31G* level. Both concerted and diradicalpathways for the retro-Diels-Alder reaction of norbornene have been examined, and the activation parametersand ¹³C primary kinetic isotope effects predicted for the concerted pathway are in excellent agreement withexperimental data. The concerted mechanism is favored over the lowest energy stepwise diradical route by12.4 kcal/mol. For the orbital symmetry-allowed suprafacial-inversion (si) pathway of the [1,3] sigmatropicrearrangement of bicyclo[3.2.0]hept-2-ene to form norbornene, a mechanism involving a transition state whichleads 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.