【摘要】 采用密度泛函理论方法在B3LYP/6-31G(d)水平上研究了Lewis碱稳定的硼代苯与一些亲二烯体的两种可能的Diels-Alder反应的微观机理和势能剖面,并研究了反应的溶剂效应和取代基效应.计算结果表明,一部分反应以直接的近同步的协同方式进行,而在另一部分反应中,两个反应物分子先形成分子间复合物,然后再经过协同的过渡态生成产物.与气相中相比,二氯甲烷溶剂使所研究的大部分反应的活化能垒有所增加.在乙炔或乙烯分子中分别引入吸电子基团CO2Me或CN能显著降低反应的活化能垒.形成一个C—B键的杂Diels-Alder反应都比相应的Diels-Alder反应在热力学和动力学上容易进行,这与实验结果一致.更多还原

【Abstract】 Density functional theory(DFT) calculations at the B3LYP/6-31G(d) level of theory were employed to study the mechanism and the potential energy surface of Diels-Alder reactions between Lewis base stabilized borabenzene and dienophiles.The solvent effect and substituent effect were also considered.The results indicate that some of the reactions take place in a simple concerted way,while other reactions will form an intermolecular complex first and then proceed through a concerted transition state to obtain final products.The studies on the solvent and substituent effects reveal that the CH2Cl2 solvent will elevate the activation barriers,while CO2Me or CN groups on C atom of acetylene or ethylene may lower the activation barriers considerably.The Diels-Alder reactions forming one C—B bond and one C—C bond are always more favorable than the corresponding Diels-Alder reactions forming two C—C bonds,both thermodynamically and kinetically,which is in agreement with experimental observation.更多还原