Induction heating enables efficient heterogeneous catalytic reactions over superparamagnetic nanocatalysts

Most catalytic processes are achieved by heating the whole reaction systems including the entire reactor,substrate and solvent, which leads to energy loss and obvious heat transfer limits. In this study, induction heating was employed to boost the catalytic Suzuki-Miyaura cross-coupling reactions by using conductive superparamagnetic microspheres with loaded Pd nanoparticles as heterogeneous catalysts. It was found that, at the same apparent reaction temperatures, the reactions by adopting the i...     

1,4-Cyclohexadiene with Pd/C as a rapid, safe transfer hydrogenation system with microwave heating

A method for the rapid, safe hydrogenation of alkenes and deprotection of benzyl ethers and carboxybenzyl amides is described using catalytic transfer hydrogenation under microwave heating conditions. Commonly available Pd/C catalyst is extremely effective with 1,4-cyclohexadiene as the hydrogen transfer source. In general, the reactions are complete within five minutes at 100 °C.     

富勒烯材料的催化作用研究进展

介绍了富勒烯材料（富勒烯和富勒烯衍生物）的催化作用研究进展,特别是催化有机反应方面,包括催化氢转移和硅氢化反应、烷烃裂解反应、氢氘互换反应、耦合和烷基转移反应等.这种新材料还可以催化产生单线态氧（1O2）的化学反应、催化非金属固氮反应、催化石墨合成金刚石的反应,同时还可催化高能燃料的燃烧过程,具有广泛的应用前景.     

Hot electron generation on metal catalysts under surface reaction: Principles,devices, and application

Transfer of charge through metal-support interfaces leads to an increase in the activity of mixed catalysts. In this review, we consider the main aspects of research aimed at studying processes that create and allow interphase transfer of highly excited (hot) charge carriers in supported catalysts, and discuss the effect of these phenomena on catalytic activity.     

The Catalytic Asymmetric Aldol Reaction

The construction of C-C bonds with complete control of the stereochemical course of a reaction is of utmost importance for organic synthesis. The aldol reaction-the simple addition of an enolate donor to a carbonyl acceptor-is one of the most powerful reactions available to the synthetic chemist. In general, control of the relative and absolute configuration of the newly formed stereogenic centers has been achieved through the use of chiral starting materials or chiral auxiliaries. In recent years the search for catalytic methods that efficiently and effectively transfer chirality information has become a major effort in synthetic organic chemistry. Two different approaches have been taken toward the catalytic asymmetric aldol reaction: biocatalysis and catalysis with small molecules. Both approaches have specific advantages and limitations, and as a result are complementary to each other. The important efforts toward both approaches are reviewed in this article.     

Initiation of cationic polymerization by photoinduced electron transfer

The objective of this paper is to discuss: (i) the general approaches to the initiation of cationic polymerization by photinduced electron transfer reactions (ii) the use of photoinduced electron transfer reactions for block copolymer synthesis. For the first, it is concluded that three general methods are currently available which involve reduction of onium salts by (a) photogenerated radicals, (b) photoexcited sensitizers or (c) electron donor compounds in charge transfer complexes. According to this view, a variety of initiating systems are discussed. For the second, recent developments on the application of photoinduced electron transfer reactions to the synthesis of block copolymer of monomers polymerizable with different mechanisms are presented.     

Silver-catalyzed decarboxylative chlorination of aliphatic carboxylic acids

Decarboxylative halogenation of carboxylic acids, the Hunsdiecker reaction, is one of the fundamental functional group transformations in organic chemistry. As the initial method requires the preparations of strictly anhydrous silver carboxylates, several modifications have been developed to simplify the procedures. However, these methods suffer from the use of highly toxic reagents, harsh reaction conditions, or limited scope of application. In addition, none is catalytic for aliphatic carboxylic acids. In this Article, we report the first catalytic Hunsdiecker reaction of aliphatic carboxylic acids. Thus, with the catalysis of Ag(Phen)(2)OTf, the reactions of carboxylic acids with t-butyl hypochlorite afforded the corresponding chlorodecarboxylation products in high yields under mild conditions. This method is not only efficient and general, but also chemoselective. Moreover, it exhibits remarkable functional group compatibility, making it of more practical value in organic synthesis. The mechanism of single electron transfer followed by chlorine atom transfer is proposed for the catalytic chlorodecarboxylation.     

Rapid reduction of heteroaromatic nitro groups using catalytic transfer hydrogenation with microwave heating

A method for the rapid, safe reduction of heteroaromatic and aromatic nitro groups to amines is described using catalytic transfer hydrogenation under microwave heating conditions. Commonly available Pd/C or Pt/C catalyst is extremely effective with 1,4-cyclohexadiene as the hydrogen transfer source. In the case of substrates containing potentially labile aromatic halogens, Pt/C is effective and results in little or no dehalogenation. In general, the reactions are complete within 5 min at 120 °C.     

Insect sex pheromones: Palladium-catalyzed synthesis of aliphatic 1,3-enynes by reaction of 1-alkynes with alkenyl halides under phase transfer conditions

Functionalized 1,3-enzynes of general formula 1 have been prepared in good yields by coupling reaction of 1-alkynes or ω-functionalized 1-alkynes halides in the presence of a catalytic amount of (PPh₃)₄Pd and Cul. The reactions, which were carried out under phase transfer conditions employing benzyltriethylammonium chloride as phase transfer agent, benzene as organic solvent and diluted aq NaOH as base, occurred with 100% stereospecificity when 1-halo-1-alkenes of defined configuration were used. Such coupling reactions have been employed to prepare some pure insect sex pheromone components or their precursors in high overall yield.     

Long‐Range Electrostatics‐Induced Two‐Proton Transfer Captured by Neutron Crystallography in an Enzyme Catalytic Site

Neutron crystallography was used to directly locate two protons before and after a pH‐induced two‐proton transfer between catalytic aspartic acid residues and the hydroxy group of the bound clinical drug darunavir, located in the catalytic site of enzyme HIV‐1 protease. The two‐proton transfer is triggered by electrostatic effects arising from protonation state changes of surface residues far from the active site. The mechanism and pH effect are supported by quantum mechanics/molecular mechanics (QM/MM) calculations. The low‐pH proton configuration in the catalytic site is deemed critical for the catalytic action of this enzyme and may apply more generally to other aspartic proteases. Neutrons therefore represent a superb probe to obtain structural details for proton transfer reactions in biological systems at a truly atomic level.     

由有机钟盐简便合成不饱和醛、酮、酰胺以及有关天然产物(英文)

本文报道有机鉮盐和各种不同的醛在固-液相转移条件下,以碳酸钾为碱,简便合成共轭不饱和醛、共轭不饱和酮以及共轭不饱和酰胺。其反应通式如下:(?)n=O,1;m=0,1 and(?)X=CHO,COCH_3,CONR~1R_2当m=0时,产物几乎全部是2E 或2E,4E 产物,当m=1时,2E,4E 或2E,4E,6E 产物为主,Z 构型产物在催化量碘作用下易异构化成 E 构型产物。以此合成方法,还合成了一些具有生物活性的天然产物。该合成方法操作简便,反应条件温和,产物高度立体选择性,产率优良,这为多烯醛,多烯酮,多烯酰胺以及有关天然产物的合成提供了实用途径。     

Calculating the True and Observed Rates of Complex Heterogeneous Catalytic Reactions

Equations of the theory of steady-state complex reactions are considered in matrix form. A set of stage stationarity equations is given, and an algorithm is described for deriving the canonic set of stationarity equations with appropriate corrections for the existence of fast stages in a mechanism. A formula for calculating the number of key compounds is presented. The applicability of the Gibbs rule to estimating the number of independent compounds in a complex reaction is analyzed. Some matrix equations relating the rates of dependent and key substances are derived. They are used as a basis to determine the general diffusion stoichiometry relationships between temperature, the concentrations of dependent reaction participants, and the concentrations of key reaction participants in a catalyst grain. An algorithm is described for calculating heat and mass transfer in a catalyst grain with respect to arbitrary complex heterogeneous catalytic reactions.     

Catalytic Hydroetherification of Unactivated Alkenes Enabled by Proton‐Coupled Electron Transfer

We report a catalytic, light‐driven method for the intramolecular hydroetherification of unactivated alkenols to furnish cyclic ether products. These reactions occur under visible‐light irradiation in the presence of an Ir^III‐based photoredox catalyst, a Brønsted base catalyst, and a hydrogen‐atom transfer (HAT) co‐catalyst. Reactive alkoxy radicals are proposed as key intermediates, generated by direct homolytic activation of alcohol O?H bonds through a proton‐coupled electron‐transfer mechanism. This method exhibits a broad substrate scope and high functional‐group tolerance, and it accommodates a diverse range of alkene substitution patterns. Results demonstrating the extension of this catalytic system to carboetherification reactions are also presented.     

On the Roles of Electron Transfer in Catalysis by Nanoclusters and Nanoparticles

Electron transfer plays a major role in chemical reactions and processes, and this is particularly true of catalysis by nanomaterials. The advent of metal nanoparticle (NP) catalysts, recently including atomically precise nanoclusters (NCs) as parts of nanocatalyst devices has brought increased control of the relationship between NP and NC structures and their catalytic functions. Consequently, the molecular definition of these new nanocatalysts has allowed a better understanding and management of various kinds of electron transfer involved in the catalytic processes. This Minireview brings a chemist‘s view of several major aspects of electron-transfer functions concerning NPs and NCs in catalytic processes. Particular focus concerns the role of NPs and NCs as electron reservoirs and light-induced antenna in catalytic processes from H₂ generation to more complex reactions and sustainable energy production.     

Mechanisms of formation of hemiacetals: intrinsic reactivity analysis

The reaction mechanism of the hemiacetal formation from formaldehyde and methanol has been studied theoretically at the B3LYP/6-311++G(d,p) level. In addition to the study of the reaction between the isolated reactants, three different kinds of catalysis have been explored. The first one examines the use of assistants, especially bridging water molecules, in the proton transfer process. The second one attempts to increase the local electrophilicity of the carbon atom in formaldehyde with the presence of a Br?nsted acid (H(+) or H(3)O(+)). The last one considers the combined effect of both catalytic strategies. The reaction force, the electronic chemical potential, and the reaction electronic flux have been characterized for the reaction path in each case. In general, it has been found that structural rearrangements represent an important energetic penalty during the activation process. The barriers for the reactions catalyzed by Br?nsted acids show a high percentage of electronic reorganization contribution. The catalytic effects for the reactions assisted by water molecules are due to a reduction of the strain in the transition state structures. The reaction that includes both acid catalysis and proton assistance transfer shows the lowest energy barrier (25.0 kJ mol(-1)).     

Expansion of the Concept of Nonlinear Effects in Catalytic Reactions Beyond Asymmetric Catalysis

The observation and investigation of nonlinear effects in catalytic reactions provides valuable mechanistic insight. However, the applicability of this method was, until now, limited to molecules possessing chirality and therefore to asymmetric synthesis. The concept of nonlinear effects is expanded to catalytic reactions beyond asymmetric catalysis by using derivatives instead of enantiomers and by considering rates instead of enantiomeric excess. Additionally, its systematic application to investigate the mechanism of catalytic reactions is presented. By exceeding the limitation to asymmetric reactions, the study of nonlinear effects can become a general tool to elucidate reaction mechanisms.     

Accelerating research into bio-based FDCA-polyesters by using small scale parallel film reactors

High Throughput experimentation has been well established as a tool in early stage catalyst development and catalyst and process scale-up today. One of the more challenging areas of catalytic research is polymer catalysis. The main difference with most non-polymer catalytic conversions is the fact that the product is not a well defined molecule and the catalytic performance cannot be easily expressed only in terms of catalyst activity and selectivity. In polymerization reactions, polymer chains are formed that can have various lengths (resulting in a molecular weight distribution rather than a defined molecular weight), that can have different compositions (when random or block co-polymers are produced), that can have cross-linking (often significantly affecting physical properties), that can have different endgroups (often affecting subsequent processing steps) and several other variations. In addition, for polyolefins, mass and heat transfer, oxygen and moisture sensitivity, stereoregularity and many other intrinsic features make relevant high throughput screening in this field an incredible challenge. For polycondensation reactions performed in the melt often the viscosity becomes already high at modest molecular weights, which greatly influences mass transfer of the condensation product (often water or methanol). When reactions become mass transfer limited, catalyst performance comparison is often no longer relevant. This however does not mean that relevant experiments for these application areas cannot be performed on small scale. Relevant catalyst screening experiments for polycondensation reactions can be performed in very efficient small scale parallel equipment. Both transesterification and polycondensation as well as post condensation through solid-stating in parallel equipment have been developed. Next to polymer synthesis, polymer characterization also needs to be accelerated without making concessions to quality in order to draw relevant conclusions.     

The nature of permeability anisotropy and catalytic activity

The phenomena of permeability anisotropy and an increase in the rates of catalytic reactions in porous membranes modified with highly dispersed catalytic systems were analyzed. A model of stochastic gas motions was proposed; this model is based on the hypothesis of the specific interaction of molecules with the inner surface of pores resulting in a nonisotropic distribution of molecules over traveling directions. The effects of asymmetric gas transfer in porous and gradient-porous membranes were considered to explain differences in the rates of heterogeneous catalytic reactions in a nanoporous membrane reactor under changes in the direction of supplying a reaction mixture. From the model proposed, it follows that the transversal diffusion of gas molecules is most probable in the porous medium of a ceramic membrane with a pore-size distribution gradient from large to small pores along the flow direction. This diffusion results in an increase in the frequency of molecular collisions with the wall of a microchannel and, correspondingly, in an increase in the contact time. The model proposed explains the intensification of a number of heterogeneous catalytic reactions performed in the porous media of catalytic porous membranes.     

Gold catalysed Suzuki-Miyaura coupling of arenediazonium o-benzenedisulfonimides

Arenediazonium o-benzenedisulfonimides have been used as efficient electrophilic partners in Au(I) catalysed Suzuki coupling reactions. The synthetic protocol is general, easy and produced either biaryls or heteroaryl arenes in good yields (51 positive examples, average yield 80%). o-Benzenedisulfonimide was recovered at the end of the reactions and was reused to prepare the starting salts for further reactions. Mechanistic insights suggest that the o-benzenedisulfonimide anion act as an electron transfer agent and promotes a catalytic cycle which does not require the presence of photocatalysts or external oxidants.