离子液体结构对Diels-Alder反应的影响

综述了不同结构离子液体对Diels-Alder反应的影响，总结了大量国内外有关离子液体中Diels-Alder反应. 分别从极性、酸性和黏度的角度分析了离子液体结构变化对Diels-Alder反应产物选择性或反应速率的影响. 讨论了离子液体中所能形成的氢键种类、咪唑类阳离子C(2)位取代情况、离子液体的Lewis酸性或Br?nsted酸性、离子液体黏度和反应体系黏度等因素的影响. 采用量子化学密度泛函理论计算了反应活化能、反应物的亲电性和过渡态C?C键长. 结果表明，离子液体的独特结构能降低反应活化能，同时增加反应过程中成键的不协同性. 指出未来的发展方向是通过对离子液体物理性质更深入的研究，基于反应机理合成功能化离子液体，进一步优化反应，发展新型、高效、绿色的Diels-Alder反应，从而扩大其应用.

Effects of Structures of Ionic Liquids on Diels-Alder Reactions

The effects of structures of ionic liquids (ILs) on Diels-Alder reactions were reviewed. A lot of research on Diels-Alder reactions carried out in ILs in the world was summarized. The effects of changes in structure of ILs on the rate and endo-selectivity of the reactions were discussed in terms of physical properties of ILs, such as polarity, acidity and viscosity. The impacts of type of hydrogen bond, proton on C(2) position of imidazolium ring, Lewis acidity or Br?nsted acidity of ILs, viscosity of ILs and reaction system were also analyzed in detail. The activation energy, electrophilicity and C?C bond length in transition state were calculated by means of density functional theory. The calculation results showed that the effect of solvent decreased the activation energy and increased the asynchronicity. Related future development lay in the synthesis of functionalized ionic liquids based on ILs physical properties and reaction mechanism to obtain new, efficient and green Diels-Alder reactions and achieve wider application.