Between a reactant rock and a solvent hard place--molecular corrals guide aromatic substitutions.
Between a reactant rock and a solvent hard place--molecular corrals guide aromatic substitutions.
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DOI：
10.1039/c3cp54079k
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发表时间：
2014-01
期刊：
影响因子：
--
通讯作者：
Yan-mei Chen;G. Chass;D. Fang
中科院分区：
文献类型：
--
作者：
Yan-mei Chen;G. Chass;D. Fang
提出了一种新的邻位羧酸镁驱动的萘甲酸芳香亲核取代反应机理，并得到了高水平密度泛函理论的支持。结果表明，速率控制方面涉及R-基团从格氏试剂Mg-原子转移到萘环上的C1-原子。这种转移由两个溶剂THF分子和萘甲酸组成的分子围栏调节，它们共同将R-基团编组到位。采用CAM-B3 LYP方法和全电子DZVP基组。溶剂处理使用隐式介电连续（PCM方法）和IDSCRF原子半径。进一步演变的溶剂模型也进行了研究，由明确的溶剂化颗粒形成一个主要的溶剂化层框架的反应中心。得到的反应障碍与实验趋势密切一致，与R-基团取代基身份回火排斥与分子畜栏，反过来调制的自由能障碍。熵对自由能贡献的动力学基础的划分是成功的实验-理论协同作用的核心。
A novel reaction mechanism is presented for an ortho-magnesium carboxylate driven aromatic nucleophilic substitution in naphthoic acids, supported by high-level density functional theory. Results show that the rate-determining aspects involve an R-group transfer from a Grignard reagent Mg-atom to the C1-atom on a naphthalene ring. This transfer is moderated by a molecular corral comprised of two solvent THF molecules and the naphthoic acid, which collectively marshal the R-group into position. The CAM-B3LYP method was employed together with the all-electron DZVP basis set. Solvent was treated using an implicit dielectric continuum (PCM method) and IDSCRF atomic-radii. Further evolved solvent models were also investigated, consisting of explicit solvating particles forming a primary solvation layer framing the reaction center. Reaction barriers obtained are in close agreement with experimental trends, with R-group substituent-identity tempering repulsion with the molecular corral, in-turn modulating the free-energy barriers. Partitioning of the dynamic bases of entropy contribution to free-energy was central to the successful experimental-theoretical synergy.