AuClx (x=1, 3)催化2-炔丙基苯酮与苯炔环化反应机理

对金属元素Au采用LanL2DZ基组,对非金属元素C,H,O,Cl采用6-31G*和6-311++G**基组,用密度泛函理论的B3LYP、B3PW91、UB3LYP方法和二阶微扰理论MP2方法研究了不同氧化态的金催化剂催化2-炔丙基苯酮与苯炔环化反应的机理.结果表明:在AuCl和AuCl3的作用下,反应均能通过4+2]和3+2]途径生成产物.但在AuCl催化下,4+2]反应途径比3+2]反应途径具有更低的活化自由能,反应主要通过4+2]途径进行;而在AuCl3催化下,4+2]反应途径与3+2]反应途径的活化自由能相近,反应通过两条途径竞争生成产物.比较AuCl和AuCl3的催化效果发现,不同氧化态的金催化剂改变了反应的机理,该反应的活化自由能在AuCl作用下比在AuCl3作用下低11.18 kJ·mol-1.对于该反应,AuCl表现出了更好的催化活性.这些计算结果和实验现象相吻合.

AuClx (x=1, 3)-Catalyzed Benzannulation Mechanisms between 2-Propynyl-hypnone and Benzyne

The AuClx (x=1,3)-catalyzed benzannulation mechanisms between benzyne and 2-propynylhypnone were investigated using B3LYP,B3PW91,UB3LYP,and the second-order Mφller-Plesset perturbation (MP2) methods with the LanL2DZ basis set for Au and the 6-31G*,6-311 ++G** basis sets for C,H,O,Cl.For the AuCl or AuCl3 catalysts the reaction occurs through both the 4 + 2] and the 3 + 2]benzannulation pathways to yield the product.With AuCl,the reaction occurs mainly through the 4 + 2]reaction pathway because of this pathway's low activation free energy.With AuCl3,the reaction occurs by the 4 + 2] and the 3 + 2] reaction pathways.These two pathways are competitive because of their close activation free energies.An analysis of these results indicates that the gold oxidation states change the reaction mechanisms and greatly influence the reaction barriers.The calculated results indicate that the AuCl catalyst is more effective than AuCl3 because in the reaction catalyzed by AuCl the activation free energy of the rate determining step is 11.18 kJ· mol-1 lower than that of the reaction catalyzed by AuCl3.These results are in good agreement with the experimental observations.