Wang Hongming, Wang Yong, Han Ke-Li, Peng Xiao-Jun
State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Science, Dalian, China.
J Org Chem. 2005 Jun 24;70(13):4910-7. doi: 10.1021/jo0479213.
The Diels-Alder (DA) reactions of various substituted ethenes (methyl vinyl ether (MVE), styrene, and methyl vinyl ketone (MVK)) with o-quinone methides (o-QM) are studied by means of density functional theory (DFT) at the B3LYP/6-31G(d,p) level. On the basis of analysis for frontier molecular orbital and comparison of the activation energies for different reaction pathways, the ortho attack modes present transition structures more stable than the meta ones. The reactivity, ortho selectivity, and asynchronicity are enhanced with the increase of the electron-releasing character of the substitute on ethene fragment. The discussions for the charge distribution and charge transfer on different transition states indicate that there are different molecular mechanisms for the different substituted ethenes. The calculations show that the effect of solvent decreases the activation energy and increases the asynchronicity. The results also indicate that the hydrogen-bond formation between chloroform and the carbonyl oxygen of the o-QM lowers the activation energies and increases the asynchronicity.
采用密度泛函理论（DFT）在B3LYP/6 - 31G(d,p)水平上研究了各种取代乙烯（甲基乙烯基醚（MVE）、苯乙烯和甲基乙烯基酮（MVK））与邻醌甲基化物（o - QM）的狄尔斯-阿尔德（DA）反应。基于前线分子轨道分析以及不同反应途径活化能的比较，邻位进攻模式呈现出比间位更稳定的过渡结构。随着乙烯片段上取代基给电子性质的增加，反应活性、邻位选择性和非同步性增强。对不同过渡态电荷分布和电荷转移的讨论表明，不同取代乙烯存在不同的分子机制。计算表明，溶剂效应降低了活化能并增加了非同步性。结果还表明，氯仿与o - QM的羰基氧之间形成的氢键降低了活化能并增加了非同步性。
