锰催化的C?C键生成反应研究进展

迄今为止,贵金属(铑、钯、钌等)在过渡金属催化的碳碳键生成反应中发挥着主导作用,然而使用廉价金属催化剂更符合可持续发展的要求。锰是地壳中含量排第三位的过渡金属,价格便宜,环境危害性小,有潜力成为贵金属催化剂的替代品并发挥其自身独特的反应性。尽管锰参与的当量反应有大量文献报道,目前锰催化的反应尤其是碳碳键生成反应的发展还不成熟,如何实现高效的催化循环是锰催化领域面临的主要难题之一。本文对锰催化的付-克烷基化反应、格氏试剂的酰化反应、偶联反应、碳金属化反应、自由基反应和碳氢键活化反应进行了综述。     

微反应器中的不对称光化学反应

化学反应的手性诱导一直备受化学家的关注,虽然不对称热化学合成和手性技术已经取得了巨大的进展,但不对称光化学反应的研究远远没有取得相应的成功.激发态寿命短、活化能低是导致其对映选择性低的主要原因.最新的研究表明,采用含手性空间或经手性修饰的微环境可以使光化学反应的立体选择性大大提高.本文针对这一热点问题,综述在微反应器中进行不对称光化学反应的研究进展.     

Chemical kinetics of reactions in the unfrozen solution of ice

Some reactions are accelerated in ice compared to aqueous solution at higher temperatures. Accelerated reactions in ice take place mainly due to the freeze-concentration effect of solutes in an unfrozen solution at temperatures higher than the eutectic point of the solution. Pincock was the first to report an acceleration model for reactions in ice,1 which successfully simulated experimental results. We propose here a modified version of the model for reactions in ice. The new model includes the total molar change involved in reactions in ice. Furthermore, we explain why many reactions are not accelerated in ice. The acceleration of reactions can be observed in the cases of (i) second- or higher-order reactions, (ii) low concentrations, and (iii) reactions with a small activation energy. Reactions with a buffer solution or additives in order to adjust ion strength, zero- or first-order reactions, or reactions containing high reactant concentrations are not accelerated by freezing. We conclude that the acceleration of reactions in the unfrozen solution of ice is not an abnormal phenomenon.     

Catalytic Asymmetric Hetero-Diels-Alder Reactions of Carbonyl Compounds and Imines

Asymmetric catalysis is a challenge for chemists: How can we design catalysts to achieve the goal of forming optically active compounds? This review provides the reader with an overview of the development of catalytic asymmetric hetero-Diels-Alder reactions of carbonyl compounds and imines. Since its discovery, the Diels-Alder reaction has undergone intensive development and is of fundamental importance for synthetic, physical, and theoretical chemists. The Diels-Alder reaction has been through different stages of development, and at the beginning of the 21st century catalytic Diels-Alder reactions are one of the main areas of focus. The preparation of numerous compounds of importance for our society is based on cycloaddition reactions to carbonyl compounds and imines. There are several parallels between the reactions of carbonyl compounds and those of imines, which, however, begin to vanish on entering the field of catalytic reactions. Why? From a mechanistic point of view some similarities can be drawn, but the synthetic development of catalytic enantioselective hetero-Diels-Alder reactions of imines are several years behind those of the carbonyl compounds. For hetero-Diels-Alder reactions of carbonyl compounds there a number of different chiral catalysts, and great progress has been achieved in developing enantioselective reactions for unactivated and activated carbonyl compounds. In contrast the development of catalytic enantioselective hetero-Diels-Alder reactions of imines is in its infancy and only few catalytic reactions have been published. This review will focus on the most important developments, and discuss the synthetic and mechanistic aspects of enantioselective hetero-Diels-Alder reactions of carbonyl compounds catalyzed by chiral Lewis acids. For the hetero-Diels-Alder reactions of imines, the diastereoselective reactions of optically substrates catalyzed by Lewis acids will be presented first, followed by the catalytic enantioselective reactions.     

Site-selectively functionalizing microelectrode arrays: the use of Cu(I)-catalysts

Site-selective Cu(I)-catalyzed reactions have been developed on microelectrode arrays. The reactions are confined to preselected electrodes on the arrays using oxygen as the confining agent. Conditions initially developed for the Cu(I)-catalyzed click reaction have proven general for the coupling of amine, alcohol, and sulfur nucleophiles to both vinyl and aryl iodides. Differences between reactions run on 1-K arrays and reactions run on 12-K arrays can be attributed to the 1-K array reactions being divided cell electrolyses and the 12-K array reactions being undivided cell electrolyses. Reactions on the 12-K arrays benefit from the use of a non-sugar-derived porous reaction layer for the attachment of substrates to the surface of the electrodes. The reactions are sensitive to the nature of the ligand used for the Cu catalyst.     

高压下配合物反应动力学

综述了高压下溶液中化学反应的活化体积△V~≠的定义和测定方法,以及作为配合物取代反应、异构化反应、电子转移反应和光化学反应机理的判据。     

A Theoretical Study on Pyrolysis and Sensitivity of Energetic Compounds(Ⅴ)--Nitro Derivatives of Methylbenzene

IntroductionThe nitro derivatives of methylbenzene are an important category of explosives, in whichTNT (2, 4, 6--trinitrotoluene) is widely--used. It is widely accepted that methyl hydrogen in m....troaromatlcs is quite active, which influences the impact sensitivity of an explosive. Gonzalezet al. [IJ found methyl substitution increases the decomposition rate over that of nitrobenzeneby an order of magnitude. Much effort has been devoted to relating electronic structure and.....impact sens…     

Characteristic reactions of group 9 transition metal compounds in organic synthesis

Group 9 metal compounds in organic synthesis have two characteristic reactions. The first occurs because the group 9 metals have a high affinity to carbon–carbon or carbon–nitrogen π‐bonds. The first type of characteristic reactions in these group 9 metal compounds includes Pauson–Khand reactions, the Pauson–Khand‐type reactions ([2 + 2 + 1] cyclization), the other cyclizations and coupling reactions. The second occurs because the group 9 metals have a high affinity to carbonyl groups. The second type of characteristic reactions includes carbonylations such as hydroformylations, the carbonylations of methanol, amidocarbonylations and other carbonylations. The first characteristic reactions are applied for the synthesis of fine chemicals such as pharmaceuticals and agrochemicals. However, the second characteristic reactions are utilized not only for fine chemicals but also for important bulk commodity chemicals such as aldehydes, carboxylic acids and alcohols. Copyright © 2009 John Wiley & Sons, Ltd.     

Selection rule in free radical reactions

The insertion and abstraction reactions are investigated on the basis of the Heisenberg model. These reactions are characterized as spin-symmetry forbidden and allowed reactions, respectively. It is pointed out that free radical reactions occur readily when there is no spin degeneracy in the course of these reactions. The rule obtained is discussed in relation to the orbital symmetry conservation rule for concerted reactions.     

Catalytic Asymmetric Dearomatization Reactions

This Review summarizes the development of catalytic asymmetric dearomatization (CADA) reactions. The CADA reactions discussed herein include oxidative dearomatization reactions, dearomatization by Diels–Alder and related reactions, the alkylative dearomatization of electron‐rich arenes, transition‐metal‐catalyzed dearomatization reactions, cascade sequences involving asymmetric dearomatization as the key step, and nucleophilic dearomatization reactions of pyridinium derivatives. Asymmetric dearomatization reactions with chiral auxiliaries and catalytic asymmetric reactions of dearomatized substrates are also briefly introduced. This Review intends to provide a concept for catalytic asymmetric dearomatization.     

A nontransmetalation reaction pathway for anionic four-electron donor-based palladacycle-catalyzed addition reactions of arylborons with aldehydes

A nontransmetalation reaction pathway for anionic four-electron donor-based (Type I) palladacycle-catalyzed addition reactions of arylborons with aldehydes is described. This new reaction pathway offers new catalysis opportunities for Type I palladacycle-catalyzed addition reactions such as the exceptionally low catalyst loading catalysis, with the catalyst loading as low as 0.0005 mol %. This new pathway may be applicable for other transition metal-catalyzed addition reactions and might lead to the development of new reactions including sequential/tandem reactions.     

Classical, phenomenological analysis of the kinetics of reactions at the gas-exposed surface of mixed ionic electronic conductors

The kinetics of reactions occurring at the gas-exposed surfaces of charged mixed ionic electronic conductors (MIECs) are examined from theoretical first principles. Analysis based on the classical electrochemical potential-transition state theory model reveals that the nature of the reactions is electrochemical in general. However, the influence of the surface potential on the reaction rate is opposite for adsorption and incorporation reactions. Two-dimensional finite volume models of an MIEC as working electrode in a half-cell configuration are presented. The results for a simple, two-step reduction process show that the effect of the surface potential on the rate of reactions is minimal for incorporation-limited reactions but more influential for adsorption-limited reactions. An erratum to this article is available at .     

Some theoretical considerations in analytical chemistry : The influence of absolute concentration on the parameters of redox titrimetry

Redox reactions are classified into symmetrical, homogeneous and inhomogeneous reactions. Reaction deficiencies when expressed as concentrations are dependent on absolute reactant concentrations, but have been proved to be independent of dilution when expressed as ratios in symmetrical and homogeneous reactions. An expression relating change of reaction deficiency with dilution for inhomogeneous reactions has been derived ; dilution of the reactants very rapidly decreases the reaction deficiency.Expressions for potentials in terms of concentration ratios have been derived for homogeneous and symmetrical reactions and prove to be independent of dilution. For inhomogeneous reactions the absolute potential falls on dilution, although the relative potential change, e.g., from the midpoint of a titration, increases asymptotically to a maximum.New derivations of the equivalence point potential and of an expression for the quantitativeness, for symmetrical and homogeneous reactions confirm the classical expressions and demonstrate their independence of dilution. For inhomogeneous reactions, methods of calculation of quantitativeness and equivalence point potentials through reaction deficiencies are proposed. For such reactions, the equivalence point potential rises sharply with dilution, giving titration curves of increasing steepness. The dependence of mid-point potentials and relative change of potential during titration upon dilution are also examined.     

Recent advances in solventless organic reactions: towards benign synthesis with remarkable versatility

A paradigm shift away from using solvents in organic synthesis as solventless reactions can lead to improved outcomes, and more benign synthetic procedures, in for example aldol condensation reactions, sequential aldol and Michael addition reactions en route to Kr?hnke type pyridines, reactions leading to 3-carboxycoumarins, benzylidenes, 4-aryl-1,4-dihydropyridines and 2-aryl-1,2,3,4-tetrahydroquinazolines, and oligomerisation reactions for the synthesis of cavitands; kinetic considerations for the reaction of two solids can only be explained if a eutectic melt is formed during the reaction.     

Three characteristic reactions of organocobalt compounds in organic synthesis

Organocobalt compounds in organic synthesis have three characteristic reactions. The first occurs because cobalt has a high affinity to carbon–carbon π‐bonds or carbon–nitrogen π‐bonds. The second occurs because cobalt has a high affinity to carbonyl groups. The third is due to cobalt easily tending to form square‐planar bipyramidal six‐coordination structures with four nitrogen atoms or two nitrogen atoms and two oxygen atoms at the square‐planar position, and to bond with one or two carbon atoms at the axial position. The first characteristic reactions are the representative reactions of organocobalt compounds with a mutually bridged bond between the two π‐bonds of acetylene and the cobalt–cobalt bond of hexacarbonyldicobalt. These are reactions with a Co₂(CO)₆ protecting group to reactive acetylene bond, the Nicholas reactions, the Pauson–Khand reactions ([2 + 2 + 1] cyclizations), [2 + 2 + 2] cyclizations, etc. These reactions are applied for the syntheses of many kinds of pharmaceutically useful compounds. The second reactions are carbonylations that have been used or developed as industrial processes such as hydroformylation for the manufacture of isononylaldehyde, and carbonylation for the production of phenylacetic acid from benzyl chloride. The third reactions are those reactions with the B₁₂‐type catalysts, and they have recently been used in organic syntheses and are utilized as catalysts for stereoselective syntheses. These reactions have been used as new applications for organic syntheses. Copyright © 2007 John Wiley & Sons, Ltd.     

Modeling chemical reactions for drug design

Chemical reactions are involved at many stages of the drug design process. This starts with the analysis of biochemical pathways that are controlled by enzymes that might be downregulated in certain diseases. In the lead discovery and lead optimization process compounds have to be synthesized in order to test them for their biological activity. And finally, the metabolism of a drug has to be established. A better understanding of chemical reactions could strongly help in making the drug design process more efficient. We have developed methods for quantifying the concepts an organic chemist is using in rationalizing reaction mechanisms. These methods allow a comprehensive modeling of chemical reactivity and thus are applicable to a wide variety of chemical reactions, from gas phase reactions to biochemical pathways. They are empirical in nature and therefore allow the rapid processing of large sets of structures and reactions. We will show here how methods have been developed for the prediction of acidity values and of the regioselectivity in organic reactions, for designing the synthesis of organic molecules and of combinatorial libraries, and for furthering our understanding of enzyme-catalyzed reactions and of the metabolism of drugs.     

镍催化偶联反应机理研究进展(英文)

近期发展了很多镍催化的偶联反应作为在有机合成中高效构建C–C键的方法,同时开展了很多关于控制镍催化反应活性和选择性的机理研究.这些研究发现,镍催化反应机理往往和相应的钯催化反应机理不同,因为镍催化偶联经常包括自由基和双金属机理.本文总结了镍催化偶联反应机理的最新进展.对于这些反应机理的理解为发展具有更高效率和选择性的镍催化偶联反应提供了帮助.     

Application of Metal-Free Dearomatization Reaction as a Sustainable Strategy to Direct Access Complex Cyclic Compounds

The highly efficient construction of complicated heterocyclic frameworks in an atom- and step-economic manner is still one of the cores of synthetic chemistry. Dearomatization reactions show the unique advantage for the construction of functionalized heterocycles and have attracted widespread attention over the past two decades. The metal-free approach has proved to be a green and sustainable paradigm for the synthesis of spirocyclic, polycyclic and heterocyclic scaffolds, which are widely present in natural products and bioactive molecules. In this review, the advances in the recent six years (2017–2023) in metal-free dearomatization reactions are highlighted. Emphasis is placed on developments in the field of organo-catalyzed dearomatization reactions, oxidative dearomatization reactions, Brønsted acid- or base-promoted dearomatization reactions, photoredox-catalyzed dearomatization reactions, and electrochemical oxidation dearomatization reactions.     

热动力学的研究 XV.分数级反主尖的热动力学法

根据热动力学基础理论和n级反应通用的势动力学方程,本文建立了各种分数级反应的热动力学研究法.应用M-340计算机编制了研究法基本公式中有关无量纲参数的各种函数表,并深入讨论了有关函数的基本性质及其图象.同时将本文建立的分数级反应研究法应用于整数级反应的热动力学研究,所得结果与文献报道的一、二级反应的无量纲参数法基本公式完全相同,该研究法还可用于判断化学反应的级数.