Mn(I)催化亚胺和炔烃脱氢偶联反应的机理研究

近年来随着过渡金属催化剂的发展和广泛使用, C—H键的活化成为了有机合成中的一大热点, 尤其是在构建有机化合物C—C键中应用广泛. 作为一种储量较大的廉价催化剂, Mn催化的C—H活化表现出巨大的应用价值和研究潜力. 我们采用密度泛函理论(DFT), 对1,4-二氧六环溶液中Mn活化C—H/N—H键实现[4+2]脱氢环化的反应机理进行了系统的研究. 我们发现该反应的催化循环包括溴负离子辅助的催化剂引发、炔烃的插入、双键迁移成环、β-H消除释放产物异喹啉以及催化脱氢循环的C—H键活化等步骤. 旨在深入理解Mn(I)活化C—H键脱氢气的具体过程, 为更多Mn催化的C—H活化反应提供理论依据.     

基于钯催化的C—H选择性官能团化构建C—C键*

近几十年来,钯催化C—H键的选择性官能团化反应已成为有机合成中构建C—C键的重要策略,基本可以分为三类反应模式：C—H键与芳基或烷基卤化物（或拟卤化物）的交叉偶联反应、C—H键之间的交叉脱氢偶联反应、C—H键与金属有机化合物的交叉偶联反应。本文综述了该领域的最新研究进展,介绍了各类反应的特点、优势及在合成中的应用,提出了今后研究和发展的重点及方向。     

Ru(II)催化有机叠氮与炔反应机理的理论研究

采用密度泛函理论, 对在Ru(II)催化剂存在下, 有机叠氮化合物和末端炔的反应机理作了深入理论研究. 在B3LYP/LANL2DZ水平上, 对该反应体系中势能面各驻点的几何构型进行了全优化计算, 并经振动频率分析确定了过渡态和中间体, 通过内禀反应坐标(IRC)的计算, 确认了反应物、中间体、过渡态和产物的相关性. 对多个反应通道的协同反应以及分步反应进行了研究. 结果表明: 协同反应通道Ic和分步反应通道IIc是反应能垒较低的反应通道, 活化自由能较其它反应通道低, 有利于1,5-二取代1,2,3-三唑的生成, 具有特定的区域选择性, 与实验结果吻合.     

Ru(II)催化有机叠氮与炔反应机理的理论研究

采用密度泛函理论, 对在Ru(II)催化剂存在下, 有机叠氮化合物和末端炔的反应机理作了深入理论研究. 在B3LYP/LANL2DZ水平上, 对该反应体系中势能面各驻点的几何构型进行了全优化计算, 并经振动频率分析确定了过渡态和中间体, 通过内禀反应坐标(IRC)的计算, 确认了反应物、中间体、过渡态和产物的相关性. 对多个反应通道的协同反应以及分步反应进行了研究. 结果表明: 协同反应通道Ic和分步反应通道IIc是反应能垒较低的反应通道, 活化自由能较其它反应通道低, 有利于1,5-二取代1,2,3-三唑的生成, 具有特定的区域选择性, 与实验结果吻合.     

锰催化苄基C—H键氟化反应机理的理论研究

采用密度泛函理论(Density Functional Theory,DFT),对锰催化剂MnIII(salene)F作用下苄基C—H键氟化反应的机理进行了深入的理论研究.对该反应中涉及到的重要中间体和过渡态的能量、Mulliken电荷分布、前线分子轨道等进行了分析.计算结果表明采用[MnIV(OH)(salene)F...     

铜催化异氰酸酯加成反应机理研究

异氰酸酯作为一种重要的单碳碳源,在合成化学中可以用于制备酰胺衍生物或杂环类化合物,其活化和转化机制是一个重要的问题.通过密度泛函理论(DFT)计算研究了亚铜催化异氰酸酯氢硼乙基化反应的机理.研究结果表明,该反应中叔丁醇亚铜是活性催化物种.反应经历了叔丁醇亚铜与硼烷转金属化、烯烃插入、异氰酸酯插入、与叔丁醇锂转金属化再生叔丁醇亚铜等步骤.其中,异氰酸酯插入为决速步,经历了一个特殊的三元环过渡态.如果使用手性的亚膦酰胺作为配体,则可实现立体选择性的异氰酸酯氢硼乙基化.对映体选择性控制步为烯烃插入,配体的空间调控决定了立体选择性.反应决速步同样是异氰酸酯插入,但相对使用卡宾配体,该过程活化能较低.因此,亚膦酰胺-亚铜催化体系可能具有较高催化活性.     

钌/镍双金属光氧化还原催化C—P键交叉偶联反应机理的理论研究

光介导的钌/镍双过渡金属光氧化还原催化策略可以实现室温条件下温和地构建C—P键,但由于金属镍的催化循环历程和外加碱的详细机理仍不够明确,本文利用密度泛函理论计算研究了二苯基氧化膦和芳基碘化物C—P键交叉偶联反应的机理.计算结果表明,结合光催化剂还原淬灭(Ru^Ⅱ-^*Ru^Ⅱ-Ru^I-Ru^Ⅱ)和镍催化循环(Ni⁰-Ni^I-Ni^Ⅲ-Ni^I-Ni⁰)的自由基机制是优势路径,其中无机碱Cs₂CO₃发挥重要作用,它辅助底物二苯基氧化膦参与光催化剂淬灭,并通过分步质子耦合电子转移过程产生重要中间体磷自由基.该研究结果有助于加深研究者对光介导的氧化还原构建C—P键偶联反应机理的认知,我们希望可以为实验化学家进一步设计过渡金属镍和光催化剂协同催化构建C—X键提供思路.     

分子筛催化cis-2-丁烯的双键异构反应机理的DFT研究

基于含有两个Si和一个Al的分子筛3T簇模型, 利用密度泛函方法(DFT)研究了分子筛催化1-丁烯双键异构为cis-2-丁烯的反应机理. 在B3LYP/6-31G(d,p)计算水平上对反应各驻点进行了全优化, 并计算了反应的活化能. 研究发现, 分子筛上的酸性OH基团首先通过物理吸附靠近1-丁烯的双键, 形成了π配位复合物后, 丁烯双键的端基C原子逐渐抽取这个质子, 同时相邻酸性位的一个O原子也抽取丁烯碳链上的一个H原子, 形成吸附态的cis-2-丁烯, 最后通过脱附形成产物, 使分子筛复原, 反应按照协同反应机理发生. 计算得到的表观活化能是55.9 kJ/mol, 与实验结果接近.     

NAMI-A乙基取代衍生物水解机理的DFT研究

采用密度泛函理论(DFT)方法,并结合导体极化连续模型(CPCM)研究了[(N-EtIm)H][trans-RuⅢCl4(DMSO)(N-EtIm)](N-EtIm=N-乙基咪唑)分别在中性及酸性条件下的水解反应过程.同时,为提高溶剂化能的精确度,在中性条件下水解反应的计算中采用3个水分子的溶剂化模型.计算得到水解反应过程中相应的结构特征和详细的热力学能量及速率常数.首先,在中性条件下,对于第一步水解,液相中配合物的活化能垒为109.9kJ/mol,速率常数为3.3×10-7 s-1,与实验中测得的第一步水解反应的速率常数(4.4×10-7 s-1)一致.对于第二步水解,反应的活化能垒为117.9kJ/mol,这符合实验中观察到的第二步水解比第一步水解反应慢的现象.其次,计算结果表明,酸性条件下,DMSO基团易于水解,Cl-水解困难,这也与实验结果相吻合.     

Cu_2O(111)催化水煤气变换反应机理的理论研究

采用密度泛函理论结合周期平板模型方法系统地研究了水煤气变换反应在Cu_2O(111)表面上的反应机理,包括氧化还原机理、羧基机理和甲酸根机理.结果表明,在Cu_2O(111)表面,羧基机理和甲酸根机理均可行,且甲酸根机理更为有利,其最佳反应途径为H_2O~*→H~*+OH~*;CO(g)+H~*+OH~*→trans-HCOOH~*(1)→cis-HCOOH~*→CO_2~*+H_2(g).其中trans-HCOOH~*(1)→cis-HCOOH~*为其决速步,该基元反应的能垒仅为59 kJ·mol~(-1).羧基机理的最优反应路径同样是以H_2O的解离反应开始,随后CO(g)+OH~*→cis-COOH~*→trans-COOH~*→CO_2(g)+H~*,最后产生的两个吸附的H原子先迁移再结合生成H_2,整个反应的控速步骤为H原子的迁移,迁移能垒为96 kJ·mol~(-1).氧化还原机理则由于OH解离需要越过一个很高的能垒(254 vs.187 kJ·mol~(-1))而不可行.     

甲氧基在Rh(111)表面吸附的密度泛函研究

采用密度泛函理论(DFT)的B3LYP方法,以原子簇Rh13(9,4)为模拟表面,在6-31G(d,p)与Lanl2dz基组水平上,对甲氧基在Rh(111)表面的四种吸附位置(fcc、hcp、top、bridge)的吸附模型进行了几何优化、能量计算、Mulliken电荷布局分析以及前线轨道的计算。结果表明,当甲氧基通过氧与金属表面相互作用时,在bridge位的吸附能最大,吸附体系最稳定,在top位转移的电子数最多;吸附于Rh(111)面的过程中C—O键被活化,C—O键的振动频率发生红移。     

甲醇在Ru(0001)表面吸附的密度泛函研究

采用密度泛函理论(DFT)的B3LYP方法,以原子簇Ru15为模拟表面,对甲醇在理想的Ru(0001)面三种吸附位置(top,fcc,hcp)的吸附模型进行了几何构型优化,能量计算,Mu lliken布局分析以及振动频率计算,结果表明顶位为最有利的吸附位.这些变化与实验观察到的甲醇在过渡金属表面解离的结果相一致.同时通过对吸附过程的分析推测其可能的解离途径.     

DFT Study on the Correlation between Thermodynamical Property and Molecular Structure of Polybromo-phenoxathiin

Complete optimization was conducted for 136 polybromo-phenoxathiin congeners(PBPTs) on the B3LYP/6-31G* level with Gaussian 03 program.The structural parameters and thermodynamical parameters of each molecule were obtained under the standard state of 298.15 K and 1.013×105 Pa.Reverse linear regression was employed to establish the quantitative structure-property correlation models between heat capacity at constant volume(CVθ),entropy(Sθ),standard heat of formation(△fHθ) and standard free energy of formation(△fGθ) of PBPTs and the structural parameters(the most negative atomic charge(q-) and molecular average polarizability(α)).These models presented better correlations(r20.97).And they were validated by variance inflation factor(VIF) and t-test,which can better explain the regularity of thermodynamical property of PBPTs,and has good stability and great prediction ability.     

1,1′-联萘-2,2′-二胺的结构和外消旋机理的DFT研究

运用电子密度泛函理论(DFT)研究了1,1′-联萘-2,2′-二胺光学构象的稳定性、消旋异构化过程及机理。研究表明:2,2′-BINAM有三种稳定构型,每一种构型都有两个镜面对映异构体。2,2′-BINAM的异构化有两种类型:一是氨基围绕离域大π键所在平面进行翻转;另一是两个萘环围绕C1-C1′键进行旋转。     

The Unexpected Mechanism Underlying the High‐Valent Mono‐Oxo‐Rhenium(V) Hydride Catalyzed Hydrosilylation of CN Functionalities: Insights from a DFT Study

In this study, we theoretically investigated the mechanism underlying the high‐valent mono‐oxo‐rhenium(V) hydride Re(O)HCl₂(PPh₃)₂ ( 1 ) catalyzed hydrosilylation of C?N functionalities. Our results suggest that an ionic S_N2‐Si outer‐sphere pathway involving the heterolytic cleavage of the Si?H bond competes with the hydride pathway involving the C?N bond inserted into the Re?H bond for the rhenium hydride ( 1 ) catalyzed hydrosilylation of the less steric C?N functionalities (phenylmethanimine, PhCH=NH, and N‐phenylbenzylideneimine, PhCH=NPh). The rate‐determining free‐energy barriers for the ionic outer‐sphere pathway are calculated to be ～28.1 and 27.6 kcal mol^?1, respectively. These values are slightly more favorable than those obtained for the hydride pathway (by ～1–3 kcal mol^?1), whereas for the large steric C?N functionality of N,1,1‐tri(phenyl)methanimine (PhCPh=NPh), the ionic outer‐sphere pathway (33.1 kcal mol^?1) is more favorable than the hydride pathway by as much as 11.5 kcal mol^?1. Along the ionic outer‐sphere pathway, neither the multiply bonded oxo ligand nor the inherent hydride moiety participate in the activation of the Si?H bond.     

DFT (density functional theory) studies on cycloisomerization of 15–membered triazatriacetylenic macrocycle

The mechanism as well the stereochemistry of cascade cycloisomerization of 15–membered triazatriacetylenic macrocycle was investigated theoretically by using M062X/6–31+G(d,p) and M062X/LANL2DZ calculations. The results showed that the mechanism and outcome of the reaction depended on the absence and presence of a transition metal catalyst. So that, in thermal-induced condition, the reaction had to experience several suprafacial concerted reactions including Ene-reaction (DG^#=35.38 kcal/mol), Diels–Alder cycloaddition (DG^# = 17.16 kcal/mol), and sigmatropic H-shift rearrangement (DG^# = 56.21 kcal/mol) to produce diastereoselective fused cis–tetracyclic aromatic bearing a pyrrole moiety by following kinetic considerations. Also, the [2+2+2] cycloaddition mechanism was neglected in thermal–induced conditions because of high activation free Gibbs energy (DG^# = 63.90 kcal/mol). In the presence of palladium catalyst, Pd(0) formed an adduct by coordinating to C = C bonds and decreased the DG^# of the process to 29.58 kcal/mol, and consequently provided a facilitated media for the reaction to follow the [2+2+2] to produce more stable fused tetracyclic benzenoid aromatic by passing through the lower energy barrier.     

DFT Study on the Electronic and Structural Properties of ReO5-/0 Clusters

The electronic and structural properties of ReO5 and ReO5 clusters are investigated using density functional theory (DFT) calculations. The lowest energy structures for both the anionic and neutral clusters are determined, and the corresponding photoelectron spectrum is simulated. Our results show that ReO5 can be described as an unusual peroxo molecule, Re(O)3(η2-O2) , while ReO5 is found to be exhibiting the O2 o radical character. Molecular orbital analyses and spin density analyses are performed to elucidate the chemical bonding and the electronic and structural properties in these two rhenium oxide clusters.     

杂双核Rh(I)-Cr配合物催化乙炔氢甲酰化反应机理的密度泛函研究

用密度泛函B3LYP方法对杂双核(CO)4Cr(μ-PH2)2RhH(CO)(PH3)配合物催化乙炔氢甲酰化反应机理进行了详细研究. 对结合和解离机理所涉及中间体和过渡态的结构进行详细分析, 在此基础上阐明了金属铬的协同性. 计算结果表明解离机理占主导地位. 乙炔氢甲酰化反应的决速步骤为炔烃插入步骤, 在298.15 K和101.325 kPa下的活化自由能为73.72 kJ/mol. 乙炔插入和醛还原消除步骤均在热力学上不可逆. Cr(CO)4部分的引入并没有改变乙炔氢甲酰化反应机理. Rh与Cr间的d轨道相互作用在反应过程起重要作用.     

1,1'-联萘-8,8'-二酚的结构和消旋机理的密度泛函研究

Density functional theory (DFT) was applied to study the ground state geometries and isomerization processes of 1,1'-binaphthalene-8,8'-diol. Three isomers, denoted as ISO1, ISO2, and ISO3, were found, distinguished by different orientations of the OH groups, and each OH-orientational isomer has R- and S- enantiomer. The conformational stabilities of these isomers were investigated by tracking the energy change with respect to the ring-to-ring torsion. The inter-conversions between the three OH-orientational S-isomers were found to have quite low barriers owing to the nearly free rotation of OH groups around the O-C single bonds. The S-R enantiomerization of ISO1 and ISO2 can take place through the ring-ring torsion around the C1-C10 single bond, either in the anti-rotation manner or in the syn-rotation manner. The barriers of the anti routes are lower than those of the corresponding syn routes by 87.95 and 75.04 kJ/mol. For the S-R enantiomerization of ISO3, only the anti route was found. The barriers for the anti route enantiomerizations of ISO1, ISO2, and ISO3 are 119.61, 120.43, and 121.59 kJ/mol, respectively. A parallel reaction mechanism via three anti enantiomerization routes was proposed for the racemization of 1,1'-binaphthalene-8,8'-diol.