Design of metal-catalyzed synthetic reactions based on theoretical calculations

1)Friedel-Crafts反应是一种典型的芳香族亲电取代反应，由刘易斯酸催化。确切的反应机理尚未阐明。因此，需要了解典型的刘易斯酸Al_2Cl_6的桥连形式的催化能力、Wheland中间体质子消除的驱动力和速率控制步骤。采用密度泛函B3 LYP方法，在6- 31 G ^* 基组水平上对氯化铝催化下苯与乙酰氯的Friedel-Crafts酰基化反应进行了计算.首先，羰基氧与Al配位，并且所得络合物异构化为酰基离子中间体（π-络合物）。亲电加成后，形成Wheland中间体（σ-络合物）。从而阐明了基本过程。2）用密度泛函和ONIOM方法研究了醇和苯酚与四甲基和均四甲苯二烯的加成反应。MeOH的二聚体比单体更容易加成到Me_2Si = SiMe_2上。三聚体不是加合物，而是两性离子中间体。在（CF_3OH）_2与Me_2Si = SiMe_2的加成反应中，H_2O的存在使H_2O的分子结构发生了变化。Si键的形成比O键更先进。Si键在过渡态（TS）形成。考察了七种苯酚衍生物对Me_2Si = SiMe_2的加成反应，发现无论苯环上的取代基如何，二聚体反应都比单体反应好。（MeOH）_2与Mes_2Si = SiMes_2反应也是有利的，反应物的异构体如配合物（前体）可以通过内旋转得到不同立体化学的加合物。通常，醇或酚的二聚体是朝向二硅烯的反应物。对二甲氨基苯酚单体与Mes_2Si = SiMes_2的反应是由于四个均三甲苯基的空间拥挤作用。

1) The Friedel-Crafts reaction is a representative electrophilic aromatic substitution reaction, catalyzed by Lewis acids. The precise reaction mechanism has not been elucidated yet. Understanding of catalytic ability of the bridged form of a typical Lewis acid Al_2Cl_6, the driving force for proton elimination of Wheland intermediate, and rate-determining step is required. B3LYP density functional theory calculations with 6-31G^* basis set of Friedel-Crafts aclylation reaction of benzene with acetyl chloride catalyzed by aluminum chloride were carried out. At first, carbonyl oxygen coordinates to Al and the resulting complex isomerizes to acylium ion intermediate (π-complex). After the electrophilic addition, Wheland intermediate (σ-complex) forms. Thus, the elementary process was elucidated. The study on Friedel-Crafts alkylation is currently under investigation.2) Density functional and ONIOM calculations of alcohol and phenol additions to two (tetramethyl and tetramesityl) dislenes were carried out. The dimer of MeOH adds to Me_2Si = SiMe_2 more readily than the monomer. The trimer gives not the adduct but a zwitter-ionic intermediate. In the (CF_3OH)_2 addition to Me_2Si = SiMe_2, the H......Si bond formation is more advanced than the O....Si bond formation at the transition state (TS). Additions of seven phenol derivatives to Me_2Si = SiMe_2 were examined, and the dimer reactions were found to be better than the monomer reaction regardless of the substituents on benzene rings. (MeOH)_2 reacts also with Mes_2Si = SiMes_2 favorably, and an isomer of the reactant like complex (precursor) may afford an adduct of the different stereochemistry via internal rotations. Generally, the dimer of the alcohol or phenol is the reactant toward the disilenes. Exceptionally, a monomer of p-(dimethylamino)phenol reacts with Mes_2Si = SiMes_2 owing to the steric congestion by four mesityl groups.