Department of Organic Chemistry, Instituto de Ciencia de Materiales de Aragón, CSIC-Univ. de Zaragoza, Calle Pedro Cerbuna, 12. 50009 Zaragoza, Spain.
Chemistry. 2011 Jan 10;17(2):529-39. doi: 10.1002/chem.201001262. Epub 2010 Nov 9.
An extensive computational study has been carried out on different catalytic systems for cyclopropanation reactions based on copper. Most DFT schemes used present drawbacks that preclude the calculation of accurate absolute kinetic properties (energy barriers) of such systems, excepting the M05 and M06 suites of density functionals. On the other hand, there is a wide range of DFT methods capable of reproducing relative energy values, which can be easily translated into selectivities. Most of the theoretical levels used tend to overestimate activation barriers, allowing the location of the transition state (TS) on the potential-energy surface (PES) of the most reactive systems, which are probably artifacts of the method. However, after a thorough analysis of the calculated PES, and the origin of the energy differences obtained for the different alkene approaches in chiral systems, it is found that energy differences are almost constant over a wide range of geometries covering the reaction channel zone in which the true TS on the Gibbs free-energy surface (GFES) lies. Therefore, many computational schemes can still be used confidently to explain and predict enantioselectivities in these systems.
已经针对基于铜的环丙烷化反应的不同催化体系进行了广泛的计算研究。大多数使用的 DFT 方案存在缺陷，无法计算这些体系的准确绝对动力学性质（能垒），除了 M05 和 M06 密度泛函系列。另一方面，有一系列能够重现相对能量值的 DFT 方法，这些方法可以很容易地转化为选择性。大多数使用的理论水平往往会高估活化能垒，从而允许在最反应性体系的势能表面 (PES) 上定位过渡态 (TS)，这可能是方法的人为产物。然而，在对计算出的 PES 进行彻底分析以及对手性体系中不同烯烃方法获得的能量差异的起源进行分析后，发现能量差异在覆盖反应通道区域的广泛几何形状范围内几乎保持不变，其中真正的 TS 位于吉布斯自由能表面 (GFES) 上。因此，许多计算方案仍然可以被自信地用于解释和预测这些体系中的对映选择性。
