Catalytic phosphorus(V)-mediated nucleophilic substitution reactions: development of a catalytic Appel reaction

Catalytic phosphorus(V)-mediated chlorination and bromination reactions of alcohols have been developed. The new reactions constitute a catalytic version of the classical Appel halogenation reaction. In these new reactions oxalyl chloride is used as a consumable stoichiometric reagent to generate the halophosphonium salts responsible for halogenation from catalytic phosphine oxides. Thus, phosphine oxides have been transformed from stoichiometric waste products into catalysts and a new concept for catalytic phosphorus-based activation and nucleophilic substitution of alcohols has been validated. The present study has focused on a full exploration of the scope and limitations of phosphine oxide catalyzed chlorination reactions as well as the development of the analogous bromination reactions. Further mechanistic studies, including density functional theory calculations on proposed intermediates of the catalytic cycle, are consistent with a catalytic cycle involving halo- and alkoxyphosphonium salts as intermediates.     

过渡金属型汽车尾气净化催化材料的制备及性能研究

采用固定床反应装置,模拟汽车尾气的组成成分,以CO/NH3为探针反应,分别研究了活性成分负载量及焙烧温度等因素对过渡金属氧化物催化材料MnOx/γ-Al2O3和Mn-Ce-O(x)/γ-Al2O3的催化活性的影响,并考察了该催化剂的抗硫化中毒性能和抗老化性能。在该研究条件下,氧化物负载量在0.12(质量分数),焙烧温度在700℃左右时,催化剂对NO-CO体系中CO的氧化率在85%以上。将催化剂在3.0%的SO2/空气气氛中强制中毒后,其对CO/NO体系中CO的催化转化率明显下降,但抗老化实验表明,该催化剂经900℃下,12%水蒸汽老化 60 h后,对CO的催化活性不仅没有下降,反而略有升高,说明该催化剂具有良好的抗老化性能和高温活性。     

Linear Alpha-Olefins by Catalytic Oligomerization of Ethylene

This paper describes a new catalytic process for linear alpha-olefins by oligomerization of ethylene using a soluble alkyl aluminum chloride-titanium tetrachloride catalyst. Important catalytic and polymerization variables, such as catalyst activity, selectivity to linear products, and molecular weight, are discussed. An ionic mechanism is proposed to explain the unusual features of this new process.     

Chemical imaging of catalytic solids with synchrotron radiation

Heterogeneous catalysis is a term normally used to describe a group of catalytic processes, yet it could equally be employed to describe the catalytic solid itself. A better understanding of the chemical and structural variation within such materials is thus a pre-requisite for the rationalising of structure-function relationships and ultimately to the design of new, more sustainable catalytic processes. The past 20 years has witnessed marked improvements in technologies required for analytical measurements at synchrotron sources, including higher photon brightness, nano-focusing, rapid, high resolution data acquisition and in the handling of large volumes of data. It is now possible to image materials using the entire synchrotron radiative profile, thus heralding a new era of in situ/operando measurements of catalytic solids. In this tutorial review we discuss the recent work in this exciting new research area and finally conclude with a future outlook on what will be possible/challenging to measure in the not-too-distant future.     

光热催化还原二氧化碳反应器研究进展

光热催化还原技术是二氧化碳资源化的研究热点之一。设计高效的新型催化剂材料,是构建有效的光热催化反应体系的重要内容,而开发与催化材料适配的反应器,则可以最大化地发挥催化剂的性能,是光热催化放大反应的关键。本文综述了光热催化反应器的不同形式,讨论了光热催化关键变量温度、光照、给料类型和运行方式对反应器设计的影响。总结了反应器设计的局限性和挑战性,为光热催化还原二氧化碳的技术发展提出了展望。     

Catalytic,theoretical, and biological investigation of an enzyme mimic model

Artificial catalyst studies were always stayed at the kinetics investigation level, in this work bioactivity of designed catalyst were shown by the induction of biomineralization of the cells, indicating the possible use of enzyme mimics for biological applications. The development of artificial enzymes is a continuous quest for the development of tailored catalysts with improved activity and stability. Understanding the catalytic mechanism is a replaceable step for catalytic studies and artificial enzyme mimics provide an alternative way for catalysis and a better understanding of catalytic pathways at the same time. Here we designed an artificial catalyst model by decorating peptide nanofibers with a covalently conjugated catalytic triad sequence. Owing to the self-assembling nature of the peptide amphiphiles, multiple action units can be presented on the surface for enhanced catalytic performance. The designed catalyst has shown an enzyme-like kinetics profile with a significant substrate affinity. The cooperative action in between catalytic triad amino acids has shown improved catalytic activity in comparison to only the histidine-containing control group. Histidine is an irreplaceable contributor to catalytic action and this is an additional reason for control group selection. This new method based on the self-assembly of covalently conjugated action units offers a new platform for enzyme investigations and their further applications. Artificial catalyst studies always stayed at the kinetics investigation level, in this work bioactivity of the designed catalyst was shown by the induction of biomineralization of the cells, indicating the possible use of enzyme mimics for biological applications.     

一种新型碱性树脂的合成

合成了一种新型药物催化剂聚氯乙烯多乙烯多胺碱性树脂(PVC-PP),其结构经IR和元素分析表征。以乙酰苯胺的N-烃基化反应考察了PVC-PP的催化性能,实验结果表明,催化剂的催化活性较好,PVC-PP在重复使用4次后催化活性基本不变。     

Catalytic performance of symmetrical and unsymmetrical sulfur-containing pincer complexes: synthesis and tandem catalytic activity of the first PCS-pincer palladium complex

The synthesis and catalytic applications of a new aryl-based unsymmetrical PCS-pincer complex are reported. Preparation of the robust air- and moisture-stable PCS-pincer palladium complex 5[X] started from the symmetrical alpha,alpha'-dibromo-meta-xylene and involved the selective substitution of one bromide by PPh(2)(BH(3)), followed by substitution of the second bromide by SPh and subsequent introduction of the palladium. The new PCS complexes (5[X]) were employed as catalysts in two important organic transformations. Firstly, complex 5[Cl] displays high catalytic activity in aldol reactions but enters the catalytic cycle as a precatalyst. Secondly, complex 5[BF(4)] displays tandem catalytic activity in the coupling of allyl chlorides with aldehydes and imines in the presence of hexamethylditin. In these tandem catalytic reactions the first process is the conversion of allyl chlorides into trimethylallyltin (and trimethyltin chloride) with Sn(2)Me(6), which is followed by catalytic allylation of aldehyde and sulfonimine substrates. In addition, we present a new catalytic process for the one-pot allylation of 4-nitrobenzaldehyde with vinyloxirane. The catalytic performance of the novel PCS-pincer palladium complex was compared to those of its symmetrical PCP- and SCS-pincer complex analogues. It was concluded that the unsymmetrical PCS complex advantageously unifies the attractive catalytic features of the corresponding symmetrical pincer complexes including both (pi-) electron-withdrawing (such as phosphorus) or (sigma-) electron-donating (such as sulfur and nitrogen) heteroatoms. Thus, in the aldol reaction the PCS-pincer palladium complex 5[X] provides a high turnover frequency, while in the tandem process both reactions are catalysed with sufficiently high activity.     

Polarographic Catalytic Wave of Lysozyme

Lysozyme(LE)isatypicalproteinwithwell-knownstrUcture.Itcontainsfourdisulfidebonds,andthreeofthemarewraPpedinsideLEmolecule.Thedisulfidebondbetweencys6andcysl27isexposedexternallyinthehydrophilicregi0n.ItwasfoundthatLEyieldedapolarograPhicwaveinO.2mollLNaAc~HAc(pH4.7)buffersolution.Therewereareductionwave(IP,c)andanoxidationwave(IP,a)inthecyclicvoltanunogram.ThepeakcurrentratiobetweenIP,aandIP,cwasl:l.ThepeakpotentialEP,cofthereductionwavewas-().53V(vs,SCE),andtheEP,aoftheoxidatio…     

Nanocarbons: Opening New Possibilities for Nano-engineered Novel Catalysts and Catalytic Electrodes

Nanocarbons find increasing relevance for the development of advanced, sometimes radically new, catalysts and catalytic electrodes. This perspective contribution discusses the potential of nanocarbons as a new class of catalytic materials, even if carbons (in the form mainly of active carbon materials) are already extensively applied as supports for catalysts. The control of nano-dimension and the improved understanding in tailoring the surface reactivity open new possibilities for their nano-engineering and the development of novel catalytic materials. With focus on the nature of the active sites in nanocarbon catalysts, we discuss here some of the novel possibilities opened by these materials to address the new challenges for catalysis deriving from moving to a more sustainable chemical and energy production.     

Function of the Metallomicelle from an Aza-Crown Ether Complex with an Acetamide Branch as a Highly Potent Promoter of Phosphate Diester Hydrolytic Cleavage

This study reports the synthesis method of a new aza-crown ether with an acetamide branch ligand, 2-(1,10-dioxa-4,7,13,16-tetraaza-cyclooctadec-4-yl)-acetamide (L), and determines the chemical composition of the cerium complex containing the aza-crown ether ligand by a new fluorescence spectrophotometric method. In the report, the cerium complex and its metallomicellar systems were used as catalysts in the hydrolysis of bis(4-nitrophenyl)phosphate ester (BNPP), and their catalytic activity was studied by the comparative method. The interaction between the metallomicelle and BNPP was proved by the fluorescence spectrum. The catalytic rate of BNPP hydrolysis was measured kinetically using the UV-Vis spectrophotometric method. The results indicated that the metallomicellar system of the anionic surfactant exhibited excellent catalytic function and relatively higher catalytic activity than that of the complex solution, the metallomicelle of nonionic and cationic surfactants, and the micelle provided an effective catalytic environment for the catalytic reaction. The experimental results also showed that the best acidity for the metallomicelle catalysis is pH 8.0, and the mono-hydroxy complex may be the real active species uaed as a catalyst in BNPP catalytic hydrolysis. The reaction mechanism was proposed on the basis of the research results.     

A simplified catalytic system for direct catalytic asymmetric aldol reaction of thioamides; application to an enantioselective synthesis of atorvastatin

A new catalytic system was developed for the direct catalytic asymmetric aldol reaction of thioamides. The new lithium-free Cu catalyst (second-generation catalyst) exhibited enhanced catalytic efficiency over the previously developed catalyst comprising [Cu(CH₃CN)₄]PF₆/Ph-BPE/LiOAr (first-generation catalyst), which required a tedious catalyst preparation process. In the reaction with the second-generation catalyst, the intermediate Cu-aldolate functioned as a Brønsted base to generate thioamide enolate, efficiently driving the catalytic cycle. The present aldol methodology culminated in a concise asymmetric synthesis of atorvastatin (Lipitor^®: atorvastatin calcium), a widely prescribed HMG-CoA reductase inhibitor for lowering low-density lipoprotein cholesterol.     

Catalytic Synthesis of N‐Unprotected Piperazines,Morpholines, and Thiomorpholines from Aldehydes and SnAP Reagents

Commercially available SnAP (stannyl amine protocol) reagents allow the transformation of aldehydes and ketones into a variety of N‐unprotected heterocycles. By identifying new ligands and reaction conditions, a robust catalytic variant that expands the substrate scope to previously inaccessible heteroaromatic substrates and new substitution patterns was realized. It also establishes the basis for a catalytic enantioselective process through the use of chiral ligands.     

Catalytic Synthesis of N‐Unprotected Piperazines,Morpholines, and Thiomorpholines from Aldehydes and SnAP Reagents

Commercially available SnAP (stannyl amine protocol) reagents allow the transformation of aldehydes and ketones into a variety of N‐unprotected heterocycles. By identifying new ligands and reaction conditions, a robust catalytic variant that expands the substrate scope to previously inaccessible heteroaromatic substrates and new substitution patterns was realized. It also establishes the basis for a catalytic enantioselective process through the use of chiral ligands.     

分子氧氧化醇的研究进展

鉴于分子氧具有经济、环保、易得的优势,本文从均相催化、多相催化以及新材料的角度阐述了近年来液态醇选择氧化到醛酮的进展。着重介绍了过渡金属作为活性组分构成的催化体系,较详细的对新催化材料的研究做了一下归类,并对其在醇的氧化反应中的应用做了介绍,认为传统催化领域的研究仍然具有魅力,同时新材料的开发与运用在未来的具有诱人的前景。     

Catalytic reactions-I Mechanisms

The mechanisms of some reactions used in catalytic analysis are discussed. The knowledge of the mechanism of a catalytic reaction can help in the development of new catalytic reactions and the choice of optimal conditions, and to show the possibilities for further increases in sensitivity.     

Trial Test of Supported Nanosized Catalyst in Catalytic Reformate Hydrotreating Reaction

Nanostructured particles are a new kind of materials whose size is less than 100 nm. It is obvious that the properties(e.g. electronic, magnetic, catalytic, optical and themal etc) of nano-particles are more excellent than those of traditional materials because of high specific surface area and special structure. Up to now, nano-particles have been studied and will be developed as a new kind of catalysts in the oil and chemical industry as well as environment protection fields. In this paper, catalytic properties of the nano-Pd/Al₂O₃ catalyst were studied for catalytic reformate hydrotreating reaction.     

Catalytic generation of activated carboxylates: direct, stereoselective synthesis of beta-hydroxyesters from epoxyaldehydes

The catalytic generation of activated carboxylates from epoxyaldehydes enables the direct, stereoselective synthesis of beta-hydroxyesters under mild, convenient reaction conditions. In addition to providing a new method for the synthesis of anti-aldol adducts, this chemistry unveils a mechanistically viable solution to the catalytic, waste-free synthesis of esters.     

Dehydrogenative oxidation of primary and secondary alcohols catalyzed by a Cp*Ir complex having a functional C,N-chelate ligand

A new catalytic system for the dehydrogenative oxidation of alcohols using a Cp*Ir complex having a functional C,N-chelate ligand has been developed. With this catalytic system, both primary and secondary alcohols were efficiently converted to aldehydes and ketones, respectively. Mechanistic investigations of this catalytic system have revealed that the catalytically active species is a hydrido iridium complex with a functional C,N-chelate ligand.     

Combinatorial Heterogeneous Catalysis-A New Path in an Old Field

Combinatorial catalysis is the systematic preparation, processing, and testing of large diversities of chemically and physically different materials libraries in a high-throughput fashion. It also embodies microfabrication, robotics, automation, instrumentation, computational chemistry, and large-scale information management (informatics), and as such carries the promise of a renaissance in catalytic reaction engineering. Significant progress has already been made in demonstrating the speed and economic advantage of combinatorial approaches by the discovery of superior catalytic materials in a matter of hours and days, as opposed to the months and years required using traditional methods. Combinatorial methods can also significantly contribute to our understanding of catalytic function by increasing our chances of discovering totally new and unexpected catalytic materials, and by expediting the recognition of trends and patterns of structure-activity relations, from which new catalytic materials can be designed more efficiently. Combinatorial catalysis undoubtedly will be the new paradigm of catalysis research as the industry faces increasing global competition and pressure for the development of environmentally friendly processes at a time when resources for research are diminishing.