共查询到20条相似文献,搜索用时 15 毫秒
1.
O. N. Temkin 《Kinetics and Catalysis》2012,53(3):313-343
The state-of-the-art in the theory of routes for multi-route reactions in the homogeneous catalysis with metal complexes is reviewed. Key problems and the possible approaches to their solution based on the Horiuti-Temkin theory of steady-state reactions, which are useful in constructing the kinetic algebraic models of multi-route processes, are discussed. A classification of the mechanisms of real processes involved in the homogeneous catalysis with metal complexes is presented. The chain mechanisms of catalytic processes, conjugated and associated reactions, and critical phenomena in the dynamics of homogeneous reactions are considered. 相似文献
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温控非水液/液两相催化,是指一类由两种或多种液态有机物组成的催化反应体系,其特点是体系的相态变化可通过温度来调控,即体系在高温时相互混溶呈均相,低温不溶分成两相,催化剂和产物分别处于两相,从而为解决均相催化剂分离难的问题开拓了一个新方向,是液/液两相催化研究领域最引人注目的进展之一.首次以"温控"为主线将氟两相催化作为温控液/液两相催化的一个特定类型纳入"温控非水液/液两相催化"范畴,并与其它通过温度来调控的有机液/液两相和作者提出的温控相分离催化串在一起作一较为详细的评述. 相似文献
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List B 《Chemical communications (Cambridge, England)》2006,(8):819-824
During the last six years the asymmetric catalysis of carbonyl transformations via iminium ion and enamine intermediates using chiral amines as organocatalysts has grown most remarkably. In this personal account an overview of this area is given. The field can be divided into two sub areas: (a) Iminium catalysis, which is typically used for cycloadditions and conjugate additions to enals and enones and (b) Enamine catalysis, which is commonly used in electrophilic alpha-substitution reactions of ketones and aldehydes. A common origin of the two catalysis principles is proposed and their recent merger in tandem sequences is discussed. 相似文献
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Crystalline solid materials are platforms for the development of effective catalysts and have shown vast benefits at the frontiers between homogeneous and heterogeneous catalysts. Typically, these crystalline solid catalysts outperformed their homogeneous analogs due to their high stability, selectivity, better catalytic activity, reusability and recyclability in catalysis applications. This point of view, comprising significant features of a new class of porous crystalline materials termed as metal‐organic frameworks (MOFs) engendered the attractive pathway to synthesize functionalized heterogeneous MOF catalysts. The present review includes the recent research progress in developing both hydrogen‐bond donating (HBD) MOF catalysts and MOF‐supported single‐site catalysts (MSSCs). The first part deals with the novel designs of urea‐, thiourea‐ and squaramide‐containing MOF catalysts and study of their crucial role in HBD catalysis. In the second part, we discuss the important classification of MSSCs with existing examples and their use in desired catalytic reactions. In addition, we describe the relative catalytic efficiency of these MSSCs with their homogeneous and similarly reported analogs. The precise knowledge of discussed heterogeneous MOF catalysts in this review may open the door for new research advances in the field of MOF catalysis. 相似文献
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模板法在纳米材料的合成过程中已成为一种非常重要的技术。利用其结构导向、骨架填充、平衡和匹配电荷等作用,可以达到精确地调控纳米材料孔道的大小、形状及结构的目的。本文主要对模板剂的种类进行了详细的分类,重点介绍了硬模板法和软模板法在合成纳米材料过程中的现状及特点,并具体介绍了模板剂在合成纳米生物材料及纳米催化剂、电化学、化工合成等方面的应用;阐述了模板法在介孔材料合成过程中的重要性,指出了目前模板剂方法存在的优缺点;提出了模板剂在超分子功能材料、光化学反应及催化工业等方面应用的纳米材料合成中的发展趋势和良好前景。 相似文献
6.
P. Putanov 《Reaction Kinetics and Catalysis Letters》1987,35(1-2):271-279
Catalyst component Interactions were considered, including their nature, classification, dependence on main factors and implications in theoretical and applied catalysis. 相似文献
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Dr. Shinobu Takizawa Prof. Dr. Harald Gröger Prof. Dr. Hiroaki Sasai 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(25):8992-8997
In recent years vanadium catalysis has been extended to a range of different and even complementary directions in asymmetric synthesis. Inspired by nature’s way to activate both substrate and reagent in many cases, the design of efficient bifunctional and dinuclear vanadium catalysts has been achieved. Furthermore, vanadium catalysis has been an early field in which “hybrid catalysts” have been studied in detail by incorporation of oxovanadium complexes into proteins, thus giving artificial enzymes. In addition, a high compatibility of vanadium with proteins enabled the use of vanadium chemocatalysts for combinations with enzyme catalysis in one‐pot, thus leading to dynamic kinetic resolutions. In this contribution, these three concepts of vanadium catalysis opening up new perspectives for asymmetric synthesis are reviewed. 相似文献
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Emil Lindbäck Sami Dawaigher Kenneth Wärnmark 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(42):13432-13481
Substrate selectivity is an important output function for the validation of different enzyme models, catalytic cavity compounds, and reaction mechanisms as demonstrated in this review. In contrast to stereo‐, regio‐, and chemoselective catalysis, the field of substrate‐selective catalysis is under‐researched and has to date generated only a few, but important, industrial applications. This review points out the broad spectrum of different reaction types that have been investigated in substrate‐selective catalysis. The present review is the first one covering substrate‐selective catalysis and deals with reactions in which the substrates involved have the same reacting functionality and the catalysts is used in catalytic or in stoichiometric amounts. The review covers real substrate‐selective catalysis, thus only including cases in which substrate‐selective catalysis has been observed in competition between substrates. 相似文献
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Transition metal catalysis is one of the most important tools to construct carbon-carbon and carbon-heteroatom bonds in modern organic synthesis. Visible-light photoredox catalysis has recently drawn considerable attention of the scientific community owing to its unique activation modes and significance for the green synthesis. The merger of photoredox catalysis with transition metal catalysts, termed metallaphotoredox catalysis, has become a popular strategy for expanding the synthetic utility of visiblelight photocatalysis. This strategy has led to the discovery of novel asymmetric transformations, which are unfeasible or not easily accessible by a single catalytic system. This contemporary area of organic chemistry holds promise for the development of economical and environmentally friendly methods for the asymmetric synthesis of chiral compounds. In this review, the advances in the enantioselective metallaphotoredox catalysis(EMPC) are summarized. 相似文献
12.
Redox‐Neutral α‐Allylation of Amines by Combining Palladium Catalysis and Visible‐Light Photoredox Catalysis 下载免费PDF全文
Jun Xuan Ting‐Ting Zeng Zhu‐Jia Feng Qiao‐Hui Deng Prof. Dr. Jia‐Rong Chen Dr. Liang‐Qiu Lu Prof. Dr. Wen‐Jing Xiao Prof. Dr. Howard Alper 《Angewandte Chemie (International ed. in English)》2015,54(5):1625-1628
An unprecedented α‐allylation of amines was achieved by combining palladium catalysis and visible‐light photoredox catalysis. In this dual catalysis process, the catalytic generation of allyl radical from the corresponding π‐allylpalladium intermediate was achieved without additional metal reducing reagents (redox‐neutral). Various allylation products of amines were obtained in high yields through radical cross‐coupling under mild reaction conditions. Moreover, the transformation was applied to the formal synthesis of 8‐oxoprotoberberine derivatives which show potential anticancer properties. 相似文献
13.
Naoya Shindoh Yoshiji Takemoto Prof. Kiyosei Takasu Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(45):12168-12179
Domino reactions have received great attention as efficient synthetic methodologies for the construction of structurally complex molecules from simple materials in a single operation. Catalysts in domino reactions have also been well studied. In these reactions, a catalyst activates the substrate(s) only once, and the structure of the product is delineated at that time. Recently, the new concept of “tandem catalysis” in domino reactions, in which catalyst(s) sequentially activate more than two mechanistically distinct reactions, has been proposed. Tandem catalysis is categorized into three subclasses: orthogonal‐, auto‐, and assisted‐tandem catalyses. Auto‐tandem catalysis is defined as a process in which one catalyst promotes more than two fundamentally different reactions in a single reactor. An overview of recent and significant achievements in auto‐tandem catalysis is presented in this paper. 相似文献
14.
P E S?rensen R A McClelland R D Gandour 《Acta chemica Scandinavica (Copenhagen, Denmark : 1989)》1991,45(6):558-566
The ring-chain tautomerism in aqueous solution of some aryl-substituted morpholinium salts (bromides), has been studied and equilibrium constants are reported. In the crystals the substrates exist entirely in their cyclic forms as hemiacetals, but in aqueous solution NMR measurements reveal that an equilibrium is established between the cyclic (hemiacetal) and the noncyclic (ketone) form, the degree of ring-opening being more pronounced with electron-donating aryl substituents at the carbonyl carbon. The kinetics of the ring-chain interconversion in water has been investigated spectrophotometrically by a 'pH jump' stopped-flow technique. General base catalysis is observed with a Br?nsted beta value apparently independent of substituent and equal to 0.60. The Hammett rho values for various base catalysts are close to those for very similar intermolecular reactions involving hemiacetal breakdown, leading to the suggestion of a 'normal' class n mechanism for base catalysis. For acid catalysis, however, a quite different situation is encountered, since no general acid but only (weak) catalysis by the hydronium ion can be detected. We believe this deviation from 'normal' general acid catalysis is caused by an electrostatic interaction, and we suggest that it might result from a change in the usual class e mechanism for general acid catalysis by a situation in which rate-limiting concerted proton transfer is replaced by rate-limiting preprotonation. This is supported by the observed drastic change in Hammett rho value for catalysis by the hydronium ion, compared with the 'normal' case. An interesting case is encountered for the 4-aminophenyl-substituted substrate, in which the amino group becomes protonated in acid solution, thus representing a new substituent. Despite this complication, the various equilibrium and rate constants may also be evaluated experimentally for this substrate. 相似文献
15.
Dr. Silvia Alonso-de Castro Dr. Alessio Terenzi Juan Gurruchaga-Pereda Prof. Luca Salassa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(27):6651-6660
Catalysis has strongly emerged in the field of medicinal inorganic chemistry as a suitable tool to deliver new drug candidates and to overcome drawbacks associated to metallodrugs. In this Concept article, we discuss representative examples of how catalysis has been applied in combination with metal complexes to deliver new therapy approaches. In particular, we explain key achievements in the design of catalytic metallodrugs that damage biomolecular targets and in the development of metal catalysis schemes for the activation of exogenous organic prodrugs. Moreover, we discuss our recent discoveries on the flavin-mediated bioorthogonal catalytic activation of metal-based prodrugs; a new catalysis strategy in which metal complexes are unconventionally employed as substrates rather than catalysts. 相似文献
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The current status, trends, and a specific role for macroligands in catalysis by heterogenized metallopolymeric complexes are considered. Relations between homogeneous catalysis, enzyme catalysis, and catalysis by heterogenized metal complexes are traced. The effects of various factors on the catalysis of the main reactions used in organic synthesis—hydrogenation, polymerization (in particular, under the action of immobilized metallocene and postmetallocene catalysts), and redox processes (such as the catalysis of oxygenation, hydroperoxide oxidation, epoxidation, and hydroformylation)—are analyzed. In this review, attention is focused on the nondestructive identification of intermediates and catalytically active species in heterogenized systems. Experimental evidence is presented in support of the fact that the high activity, stability, and selectivity of immobilized catalysts are associated with a dramatic inhibition of concerted reactions in the coordination sphere of a transition metal, which result in catalyst deactivation, as well as with substrate enrichment. Prospects for the development of these highly organized hybrid systems and possibilities to consider the main requirements imposed on metal complex catalysis even at the stage of designing them are predicted. 相似文献
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In this review, we comprehensively describe catalyzed multicomponent reactions (MCRs) and the multiple roles of catalysis combined with key parameters to perform these transformations. Besides improving yields and shortening reaction times, catalysis is vital to achieving greener protocols and to furthering the MCR field of research. Considering that MCRs typically have two or more possible reaction pathways to explain the transformation, catalysis is essential for selecting a reaction route and avoiding byproduct formation. Key parameters, such as temperature, catalyst amounts and reagent quantities, were analyzed. Solvent effects, which are likely the most neglected topic in MCRs, as well as their combined roles with catalysis, are critically discussed. Stereocontrolled MCRs, rarely observed without the presence of a catalytic system, are also presented and discussed in this review. Perspectives on the use of catalytic systems for improved and greener MCRs are finally presented. 相似文献
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The bifunctional acid-base and monofunctional base catalysis by formamidine of 1,3-proton transfer reactions in propene has been studied with the CNDO/2 MO-method. Energy profiles for both types of catalysis were studied, and no reaction intermediate was found in either case. In agreement with orbital correlation considerations, bifunctional catalysis is preferred over monofunctional catalysis. Comparison is made with another reaction in which simultaneous transfer of two protons occurs. The mechanism of bifunctional monofunctional catalysis is discussed. 相似文献