2,3-联烯醇及其衍生物的反应

2,3-联烯醇是一类含1,2-二烯官能团和羟基的化合物, 具有很高的反应活性, 它及其衍生物是一类重要的联烯化合物. 概述了2,3-联烯醇及其衍生物的反应, 包括2,3-联烯醇在过渡金属催化下的自身异构环化反应、钯催化的偶联反应、钌催化的环羰基化反应、不同条件下不同方式的扩环反应、亲电试剂参与的反应、分子内环加成反应、自由基反应等和2,3-联烯醇衍生物在零价钯催化下基于亚甲基-π-烯丙基钯中间体生成联烯或1,3-共轭二烯的区域选择性反应, S_N2'类型的加成-消除反应, 二价钯催化下的分子内环化反应以及重排反应等.     

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.     

Three types of reactions with intramolecular five-membered ring compounds in organic synthesis

There are three types of reactions with intramolecular five-membered ring compounds in organic syntheses: The first type is reactions involving intramolecular five-membered ring compounds which are utilized for the ease of synthesis of these compounds and the stability of the products. The second is reactions performed via intramolecular five-membered ring intermediates, because such intermediates are very reactive and labile compounds. The third is the metal-catalyzed reactions with the intramolecular five-membered ring compounds because these metal compounds have catalytic activities. The third type reactions involving intramolecular five-membered ring pincer compounds are also provided.The first type reactions include carbonylations, alkenylations, alkynylations, acylations, isocyanations, Diels-Alder reactions, etc. The second type reactions include carbonylations, cross-coupling reactions, hydroacylations, ring expansion reactions, carbocyclizations, etc. The third type reactions include cross-coupling reactions, rearrangements, metatheses, reductions, Michael reactions, dehydrogenations, Diels-Alder reactions, etc.     

金属有机化学中的绿色化学反应进展

着重综述了金属有机化学领域中所涉及的与绿色化学概念有关的一些化学反应,如水相反应、超临界流体及离子液体中的反应、固态反应、原子经济性及过渡金属催化的有机反应。     

Some uses of mischmetall in organic synthesis

Mischmetall, an alloy of the light lanthanides, has been used in a variety of organic reactions, either as a coreductant in samarium(II)-mediated reactions (Barbier and Grignard-type reactions, pinacolic coupling reactions) or as the promoter of Reformatsky-type reactions. It has been also employed as the starting material for easy syntheses of lanthanide trihalides, the reactivity of which has been explored in Imamoto and Luche–Fukuzawa reactions and in Mukaiyama aldol reactions.     

Competition of monomolecular and bimolecular reactions of the alkyl radicals of artemisinin

The competition between monomolecular and bimolecular reactions of alkyl radicals of artemisinin is considered theoretically. The enthalpies of these reactions are calculated. The activation energies and rate constants of intramolecular hydrogen atom transfer, of the decyclization of the alkyl radicals of artemisinin, and of the bimolecular reactions of these radicals with C-H, S-H, and O-H bonds of biological substrates and their analogues are calculated in the framework of the parabolic model. The intramolecular hydrogen transfer reactions proceed at the highest rate. The bimolecular reactions occur somewhat less rapidly. The fastest of them are the reactions of the alkyl radicals with the thio groups of cysteine. The decyclization reactions of all artemisinin alkyl radicals are very slow.     

MNDO study of reaction paths: Hydroboration of carbonyl systems

The hydroboration reactions of acetaldehyde and acetone have been investigated by the MNDO method. The reactions have been shown to be twostep reactions involving an intermediate adduct. This adduct subsequently undergoes hydrogen rearrangement. The hydroboration reactions of acetaldehyde and acetone have been compared with the corresponding reaction of formaldehyde. The charge transfer effects accompanying these reactions have also been discussed.     

Reactivity of free clusters

Recent studies of the reactions of free or isolated transition metal clusters with simple molecules will be reviewed. Cluster chemical reactions are carried out in a laser-vaporization cluster source coupled to a continuous-flow reactor. Reactions can be categorized as chemisorptive (or surface) reactions, and bulk reactions. Chemisorptive reactions can be characterized asfacile, in which most cluster sizes of a given metal are equally reactive towards a particular reagent, oractivated, in which strong dependence of reactivity on cluster size is found. Under the normal operating conditions of the cluster reactor, a reaction may be kinetically controlled or at equilibrium. Following chemisorption, adsorbate decomposition and product desorption may occur. Specific reactions to be discussed include the reactions of iron clusters with ammonia and with water and the reactions of nickel clusters with ammonia.     

光诱导电子转移反应在有机合成中的应用

对近十年来报道的在有机合成中有重要意义的光诱导电子转移反应做了简要的总结. 包括六个部分: (1)光诱导电子转移(PET)反应的基本原理, (2) PET诱导的自由基离子裂解和去保护基反应, (3) PET诱导的加成和环加成反应, (4) PET诱导的环化反应和串联环化反应, (5)不对称PET反应, (6)微反应器中的PET反应.     

基本化学反应形式的系统分类

The old classification of basic chemical reactions was evaluated and a new systematic classification of basic reactions was proposed.In the new classification,all the chemical reactions were divided into oxidation-reduction reactions and non-oxidation-reduction reactions,and both can be divided into combination reaction,decomposition reaction and replacement reaction,respectively.In addition,a new class of basic reactions,the complicated decomposition reaction,was appended to reaction system.     

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.     

Intramolecular reactions of free radicals formed from artemisinin

Two cyclic alkoxyl radicals are formed as a result of peroxide bridge scission in artemisinin. Intramolecular reactions of these radicals induce the cascade of reactions of isomerization, decyclization, and decomposition of formed free radicals. It includes 14 reactions of intramolecular free radical hydrogen transfer, 17 reactions of decyclization of alkoxyl and alkyl radicals, and 4 reactions of decomposition of alkoxyl, acyl, and carboxyl radicals. The enthalpies of these 35 reactions are calculated. Using intersection parabolas method, activation energies and rate constants of all these reactions are calculated. The most rapid reactions are selected for every intermediate free radical. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 554–565, 2005     

Kinetics and thermodynamics of the exchange reactions of peroxy radicals with hydroperoxides

The enthalpies and equilibrium constants of the exchange reactions of peroxy radicals with hydroperoxides of various structures are calculated. The experimental data on the reactions of hydrogen atom abstraction by the peroxy radicals from the hydroperoxides are analyzed, and the kinetic parameters characterizing these reactions are calculated using the intersecting parabolas method. The activation energies and rate constants for nine reactions of H atom abstraction by a peroxy radical from the OOH group of a peroxide are calculated using the above parameters. The geometric parameters of the transition states for the reactions are calculated. The low triplet repulsion plays an important role in the fast occurrence of the reactions. The polar interaction in the transition state is manifested in the reactions of the peroxy radicals with hydroperoxides containing a polar group.     

Role of Frontier Molecular Orbital Symmetry of Reagents in Redox Catalytic Indicator Reactions

Some hypotheses are discussed for the nature of “inhibited” or “kinetically hindered” redox reactions, which are employed as indicator reactions in kinetic analytical methods. Some reactions are considered as examples to demonstrate that redox reactions are kinetically hindered because the key frontier orbitals of the reagents differ in their symmetry types. It is suggested that the redox reactions of this type be considered forbidden by inconsistency between the symmetry types of the key frontier orbitals.     

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 .     

Anodic coupling reactions: the use of N,O-ketene acetal coupling partners

Intramolecular anodic olefin coupling reactions utilizing N,O-ketene acetals have been studied. Coupling reactions with both enol ether and allylsilane terminating groups were examined. The reactions involving the coupling of the N,O-ketene acetals with allylsilane groups were found to be much more efficient than corresponding reactions utilizing dithioketene acetal groups and allylsilanes. The reactions were also more efficient than the intramolecular coupling reactions between enol ethers and allylsilanes studied earlier.     

Classification of Clock Reactions

Autocatalytic systems are sometimes designated as clock reactions or reactions that exhibit clock behavior. To resolve the recent dispute over the term clock reaction, we describe a new approach to classify systems featuring clock behavior into three distinct groups: substrate‐depletive clock reactions, autocatalysis‐driven clock reactions, and systems that have pseudo clock behavior. Many of the well‐known classical and recently discovered reactions can conveniently be put into these categories. We also provide a convincing argument for classifying some autocatalytic processes as clock reactions, but it does not necessarily mean that all autocatalytic processes should be classified as autocatalysis‐driven clock reactions. This classification can be conveniently performed if the kinetic nature of the given system has been completely elucidated and understood.     

炔烃分子内环化反应合成含氮杂环化合物研究进展

分子内氮原子参与的炔烃环化反应是构成含氮杂环化合物(例如吲哚类化合物等)的最重要途径之一. 从两个方面对分子内氮杂原子与炔的环化反应研究新进展进行了综述: 过渡金属催化分子内环化反应和分子内亲电环化反应. 此外, 对环化反应的机理也做了较详细的描述.     

Stepwise activation of "non-innocent" Cp* substituents--a Cp* based cascade reaction

Reactions of Cp* substituted pentelidene complexes with the primary phosphine Cp*PH(2) yield novel polycyclic phosphorus/arsenic and carbon containing cage compounds via cascade-like reactions. These reactions include a sequence of nucleophilic addition reactions, intramolecular hydrophosphination (partially hydroarsination) reactions, retro-Diels-Alder reactions with Cp*H elimination and subsequent [2+4]-cycloadditions.     

Building addressable libraries: site-selective use of Pd(0) catalysts on microelectrode arrays

Site-selective Pd(0)-catalyzed reactions have been developed to functionalize a microelectrode array. Heck, Suzuki, and allylation reactions have all been accomplished. The reactions are compatible with both 1K and 12K arrays and work best when a nonsugar porous reaction layer is used. Suzuki reactions are faster than the Heck reactions and thus require more careful control of the reactions in order to maintain confinement. The allylation reaction requires a different confining agent than the Heck and Suzuki reactions but can be accomplished nicely with quinone as an oxidant for Pd(0).