金催化的吲哚与末端炔烃的分子间烷基化反应

尝试了用金(Au)催化吲哚和炔烃的Friedel-Crafts烷基化反应, 具体探讨了金(I)配合物催化吲哚与末端炔烃的烷基化反应的条件, 并制备了一系列尚未见文献报道的双取代β-吲哚烷基化衍生物. 产物的结构经1H NMR, 13C NMR, MS和元素分析确证. 并对其反应机理可能性进行了推测.     

The Mechanism of Gold(I)‐Catalyzed Hydroalkoxylation of Alkynes: An Extensive Experimental Study

An extensive experimental study of the mechanism of gold(I)‐catalyzed hydroalkoxylation of internal alkynes has been conducted by using NMR spectroscopy. This study was focused on the organogold intermediates, observations of actual catalytic intermediates in situ, and the reaction kinetics that are involved in this reaction. Based on the experimental results, a complete mechanistic picture was established, including on‐ and off‐cycle processes that explain the role of diaurated species. We have shown that gold‐catalyzed hydroalkoxylation of internal alkynes is a reaction that requires only one gold atom for the catalytic cycle, disproving a recent hypothesis regarding the involvement of cooperative gold catalysis.     

Study on the mechanism of catalytic synthesis of dimethyldichlorosilane by AlCl3/MIL‐53(Al)@γ‐Al2O3

Dimethyldichlorosilane, one of the most consumed organosilicon monomers in the industry, can be prepared in a highly efficient and environmentally friendly synthesis method of disproportionating methylchlorosilanes. However, the internal mechanism of the reaction remains unclear. In this paper, the mechanism catalyzed by AlCl₃/MIL‐53(Al) and AlCl₃/MIL‐53(Al)@γ‐Al₂O₃ catalysts was calculated at B3LYP/6‐311++G(3df, 2pd) level by using the density functional theory (DFT). The results showed that although the two catalysts had similar active structures, the catalytic effects were significantly different. The Lewis acid center on the surface of γ‐Al₂O₃ in the core‐shell catalyst is complementary to the classic Lewis acid AlCl₃ through the spatial superposition effect, which greatly improves the Lewis acid catalytic activity of AlCl₃/MIL‐53(Al)@γ‐Al₂O₃.     

Platinum‐Catalyzed Asymmetric Ring‐opening Reaction of Oxabenzonorbornadiene with Terminal Alkynes

A novel platinum‐catalyzed asymmetric ring‐opening reaction of oxabenzonorbornadiene with terminal alkynes is described. The reaction affords optically active cis‐2‐alkynyl‐1,2‐dihydronaphthalen‐1‐ols in moderate yields with good enantioselectivity in the presence of catalytic amounts of Pt(COD)Cl₂/(S)‐BINAP and an excess of zinc powder. The products were obtained exclusively with the relative cis‐configuration of the ring substituents and the prevalent (1R,2S)‐configuration of the stereocenters, as determined by single crystal X‐ray diffraction analysis.     

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.     

杂双核Rh(I)-Cr配合物催化乙烯氢甲酰化反应机理的理论研究

本文采用密度泛函理论研究了杂双核HRh(CO)(PH3)(m-PH2)2Cr(CO)4配合物催化乙烯氢甲酰化反应的机理。分别研究了结合机理和解离机理,并对两个机理进行比较。计算结果表明Cr(CO)4片段的引入并没有改变简单烯烃氢甲酰化反应的机理。解离机理占主导地位。羰基插入是整个反应的决速步骤,且在298.15 K和101.325 kPa下,其活化自由能为91.15 kJ/mol。醛的还原消除步骤是不可逆的。这些结果与以前的理论和实验研究结果一致。     

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.     

Electronic Excitation of [(μ4‐η2‐alkyne)Rh4(CO)8(μ‐CO)2]: An In Situ UV/Vis Spectroscopy,Spectral Reconstruction and DFT Study

Reactions of three alkynes, namely, 1‐heptyne, 3‐hexyne and 1‐phenyl‐1‐butyne, with [Rh₄(CO)₉(μ‐CO)₃] are performed in anhydrous hexane under argon atmosphere with multiple perturbations of alkynes and [Rh₄(CO)₉(μ‐CO)₃]. The reactions are monitored by in situ UV/Vis spectroscopy, and the collected electronic spectra are further analyzed with the band‐target entropy minimization (BTEM) family of algorithms to reconstruct the pure component spectra. Three BTEM estimates of [(μ₄‐η²‐alkyne)Rh₄(CO)₈(μ‐CO)₂], in addition to that of [Rh₄(CO)₉(μ‐CO)₃], are successfully reconstructed from the experimental spectra. Time‐dependent density functional theory (TD‐DFT) predicted spectra at the PBE0/DGDZVP level are consistent with the corresponding BTEM estimates. The present study demonstrates that: 1) the BTEM family of algorithms is successful in analyzing multi‐component UV/Vis spectra and results in good spectral estimates of the trace organometallics present; and 2) the subsequent DFT/TD‐DFT methods provide an interpretation of the nature of the electronic excitation and can be used to predict the electronic spectra of similar transition organometallic complexes.     

Computational Study of Benzosultam Formation through Gold(I)-Catalyzed Ammoniumation/Nucleophilic Substitution Reaction

The Au(I)-catalyzed reactions of (2-alkynyl)phenylsulfonyl azetidines bearing terminal and non-terminal alkynes in the presence of methanol as protic nucleophile to form benzosultams derivatives were studied by density functional theory (DFT) calculations. Our study highlights that gold(I) catalyzed nucleophilic addition of the nitrogen on the alkyne is favored over the direct ring opening of the azetidine by methanol, confirming the ammonium-based mechanism. In addition, the reverse regioselectivity observed experimentally where non-terminal alkynes favors the formation of 6-endo-dig-benzosultams while terminal alkynes favor 5-exo-dig products is also explored through two different scenarios. The first one embraces the classical activation of the alkyne by a single Au(I) species while the second one tackles the formation of a σ,π-digold acetylide complex. Calculations identify both pathways as competitive although only mono Au(I) complexes can lead to final products, in good agreement with experimental observation. Further details on the importance of the presence of an excess of the protic nucleophile on the protodemetallation step and the final aminal formation is also discussed.     

Reaction Mechanism for the Dual Gold‐Catalyzed Synthesis of Dibenzopentalene: A DFT Study

A wide range of gold‐catalyzed reactions based on a dual activation mechanism has recently been reported in the literature. Herein, we present a computational investigation of the mechanism for the formation of dibenzopentalenes from 1‐ethynyl‐2‐(phenylethynyl)benzene. Transition states have been found, which substantiate the dual activation mechanism previously published and furthermore point towards a continuous presence of two gold moieties throughout the mechanistic cycle, an observation of high importance for all reactions in the field of dual activation. The initial activation of the diyne has been shown to proceed via an intermolecular transfer of a cationic gold catalyst from the thermodynamically preferred geminal‐σ,π‐acetylide complex to the active non‐geminal analogue. Furthermore, the regioselectivity of a 5‐endo versus a 6‐endo cyclization has been addressed, and the 5‐endo cyclization was found to be most favorable both thermodynamically and with regard to the activation barrier.     

Gold(I)‐Catalyzed Diastereo‐ and Enantioselective Synthesis of Polysubstituted Pyrrolo[3,4‐d][1,2]oxazines

A gold(I)‐catalyzed highly diastereo‐ and enantioselective intermolecular cycloaddition of oxime ethers with nitrones under mild conditions was developed, which provides an facile access to optically pure highly substituted pyrrolo[3,4‐d][1,2]oxazines. The salient features of this reaction include general substrate scope, high efficiency, high enantioselectivity, readily available starting materials, and the use of commercially available ligand.     

Development of Protein‐Cage‐Based Delivery Nanoplatforms by Polyvalently Displaying β‐Cyclodextrins on the Surface of Ferritins Through Copper(I)‐Catalyzed Azide/Alkyne Cycloaddition

Protein cages are spherical hollow macromolecules that are attractive platforms for the construction of nanoscale cargo delivery vehicles. Human heavy‐chain ferritin (HHFn) is modified genetically to control the number and position of functional groups per cage. 24 β‐CDs are conjugated precisely to the modified HHFn in specific locations through thiol‐maleimide Michael‐type addition followed by copper(I)‐catalyzed azide/alkyne cycloaddition (CuAAC). The resulting human ferritins displaying β‐CDs (β‐CD‐C90 HHFn) can form inclusion complexes with FITC‐AD, which can slowly release the guest molecule reversibly in a buffer solution via non‐covalent β‐CD/AD interactions. β‐CD‐C90 HHFn can potentially be used as delivery vehicles for insoluble drugs.

     

Azocinoindole Synthesis by a Gold(I)‐Catalyzed Ring Expansion of 2‐Propargyl‐β‐Tetrahydrocarboline

A new methodology taking advantage of gold(I)‐catalyzed ring expansion has been developed to assemble tricyclic 1H‐azocino[5,4‐b]indoles from 2‐propargyl‐β‐tetrahydrocarbolines. The azocinoindoles were obtained in moderate to excellent yields; the structure of which was established by X‐ray crystallographic analysis. A mechanism involving regioselective intramolecular hydroarylation, [1,2]‐alkenyl migration and carbon–carbon bond‐fragmentation was proposed.     

Mechanistic study on gold(I)‐catalyzed crosscoupling of diazo compounds: A DFT study

The reaction mechanisms of the gold(I)‐catalyzed cross‐coupling reaction of aryldiazoacetate R1 with vinyldiazoacetate R2 leading to N‐substituted pyrazoles have been theoretically investigated using density functional theory calculations. Two possible reaction mechanisms were examined and discussed. The preferred reaction mechanism (mechanism A) can be characterized by five steps: the formation of the gold carbenoid A2 via the attack of catalyst to R1 (step I), nucleophilic addition of another reactant R2 to generate intermediate A3 (step II), intramolecular cyclization of A3 to form intermediate A4 (step III), hydrogen migration to give intermediate A5 (step IV), and catalyst elimination affording the final product P1 (step V). Step IV is found to be the rate‐determining step with an overall free energy barrier of 28.3 kcal/mol. Our calculated results are in good agreement with the experimental observations. The present study may provide a useful guide for understanding these kinds of gold(I)‐catalyzed cross‐coupling reactions of diazo compounds.     

Gold(I)‐Catalyzed Diastereoselective Hydroacylation of Terminal Alkynes with Glyoxals

The reaction of an α‐ketoaldehyde and a terminal alkyne in the presence of piperidine and a catalytic amount of AuCl delivers 1,2‐dicarbonyl‐3‐enes, products of the formal hydroacylation of the triple bond. The scope of the method is broad; different aryl substituents on the dicarbonyl unit and on the alkyne are well tolerated. The products can be transformed selectively into vinylquinoxalines. Mechanistic studies, including isotope‐labeling experiments, indicate that after an initial A³‐type conversion to propargylic amines, a subsequent base‐mediated alkyne‐to‐allene isomerization and a hydrolysis of the enamine substructure during the workup deliver the formal hydroacylation products.     

Mechanism of Ethylene Migratory Insertion and Dimerization Catalyzed by δ‐Alkyl Platinum Complexes–A DFT Study

The mechanism of ethylene insertion reactions catalyzed by cationic δ‐alkyl platinum complexes has been studied at the B3LYP level of density functional theory. The initial steps of the reactions proceed via the coordination of ethylene to the reactants L₂Pt(II)R⁺, where L₂=none, (NH₃)₂, (CHNH)₂; R=H, CH₃, C₂H₅ in which ethylene coordinates strongly to the complexes PtCH⁺₃ and PtC₂H⁺₅ (coordination energies (CE) are 296.52 and 229.28 kJ/mol, respectively), while nitrogen‐containing ligands decrease the energies: Pt(NH₃)₂CH⁺₃ (CE: 180.04 kJ/mol), Pt(NH₃)₂C₂H⁺₅ (CE: 97.86 kJ/mol), Pt(CHNH)₂CH⁺₃ (CE : 176.31 kJ/mol) and Pt(CHNH)₂C₂H⁺₅ (CE: 91.00 kJ/mol). Moreover, ethylene insertion into the Pt‐alkyl bond, which is the rate‐determining step, is endothermic with barrier heights for L₂PtCH₃(C₂H₄)⁺ decreasing in the order: PtCH⁺₃ (164.18 kJ/mol)>(NH₃)₂ PtCH⁺₃ (129.95 kJ/mol)>(CHNH)₂ PtCH⁺₃ (115.27 kJ/mol), which has the same tendency for the ethyl case. The insertion product will continually undergo β‐hydride elimination, which is exothermic. On the other hand, the effects of solvent (dichloromethane, THF and benzene) are investigated with PCM method, but the inclusion of the effects in the computations only slightly affects the results. Beside that, a complete catalytic cycle for ethylene dimerization is studied in detail and the calculations agree well with known energetic and recognized tendencies.