Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095-1569, United States.
J Org Chem. 2017 Feb 17;82(4):1912-1919. doi: 10.1021/acs.joc.6b02524. Epub 2017 Feb 9.
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 higher than those of cyclic 2-azadienes, and the reaction free energies are 17-20 kcal mol 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.
用密度泛函理论（M06-2X/6-311G(d,p)）研究了丁二烯、环戊二烯、呋喃、噻吩、吡咯及其 1-氮杂和 2-氮杂衍生物与乙烯和富马腈的 Diels-Alder 反应的反应活性。环状 1-氮杂二烯的 Diels-Alder 反应的活化自由能比环状 2-氮杂二烯高 10-14 kcal mol，反应自由能更加是吸能 17-20 kcal mol。扭曲/相互作用模型表明，环状 1-氮杂二烯的活化能增加源于过渡态扭曲能的增加和 C=N 键氮端加成引起的不利相互作用能的增加。
