Origins of the Unfavorable Activation and Reaction Energies of 1-Azadiene Heterocycles Compared to 2-Azadiene Heterocycles in Diels–Alder Reactions

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• 作者：Jason S. FellBlanton N. Martin ; K. N. Houk
• 刊名：Journal of Organic Chemistry
• 出版年：2017
• 出版时间：February 17, 2017
• 年：2017
• 卷：82
• 期：4
• 页码：1912-1919
• 全文大小：644K
• ISSN：1520-6904

文摘

The reactivities of butadiene, cyclopentadiene, furan, thiophene, pyrrole, and their 1-aza- and 2-aza-derivatives in Diels–Alder reactions with ethylene and fumaronitrile were investigated with density functional theory (M06-2X/6-311G(d,p)). The activation free energies for the Diels–Alder reactions of cyclic 1-azadienes are 10–14 kcal mol^–1 higher than those of cyclic 2-azadienes, and the reaction free energies are 17–20 kcal mol^–1 more endergonic. The distortion/interaction model shows that the increased activation energies of cyclic 1-azadienes originate from increased transition state distortion energies and unfavorable interaction energies, arising from addition to the nitrogen terminus of the C═N bond.