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Organometallic synthesis, reactivity and catalysis in the solid state using well-defined single-site species

Pike, Sebastian D.; Weller, Andrew S.
Fonte: The Royal Society Publishing Publicador: The Royal Society Publishing
Tipo: Artigo de Revista Científica
Publicado em 13/03/2015 Português
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Acting as a bridge between the heterogeneous and homogeneous realms, the use of discrete, well-defined, solid-state organometallic complexes for synthesis and catalysis is a remarkably undeveloped field. Here, we present a review of this topic, focusing on describing the key transformations that can be observed at a transition-metal centre, as well as the use of well-defined organometallic complexes in the solid state as catalysts. There is a particular focus upon gas–solid reactivity/catalysis and single-crystal-to-single-crystal transformations.

Recent Advances in Nickel Catalysis

Tasker, Sarah Z.; Standley, Eric A.; Jamison, Timothy F.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/05/2014 Português
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The field of nickel catalysis has made tremendous advances in the past decade. There are several key properties of nickel that have allowed for a broad range of innovative reaction development, such as facile oxidative addition and ready access to multiple oxidation states. In recent years, these properties have been increasingly understood and leveraged to perform transformations long considered exceptionally challenging. Herein, we discuss some of the most recent and significant developments in homogeneous nickel catalysis with an emphasis on both synthetic outcome and mechanism.

Mechanical catalysis on the centimetre scale

Miyashita, Shuhei; Audretsch, Christof; Nagy, Zoltán; Füchslin, Rudolf M.; Pfeifer, Rolf
Fonte: The Royal Society Publicador: The Royal Society
Tipo: Artigo de Revista Científica
Publicado em 06/03/2015 Português
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Enzymes play important roles in catalysing biochemical transaction paths, acting as logical machines through the morphology of the processes. A key challenge in elucidating the nature of these systems, and for engineering manufacturing methods inspired by biochemical reactions, is to attain a comprehensive understanding of the stereochemical ground rules of enzymatic reactions. Here, we present a model of catalysis that can be performed magnetically by centimetre-sized passive floating units. The designed system, which is equipped with permanent magnets only, passively obeys the local causalities imposed by magnetic interactions, albeit it shows a spatial behaviour and an energy profile analogous to those of biochemical enzymes. In this process, the enzyme units trigger physical conformation changes of the target by levelling out the magnetic potential barrier (activation potential) to a funnel type and, thus, induce cascading conformation changes of the targeted substrate units reacting in parallel. The inhibitor units, conversely, suppress such changes by increasing the potential. Because the model is purely mechanical and established on a physics basis in the absence of turbulence, each performance can be explained by the morphology of the unit...

The Role of Active Site Residues in ATP Binding and Catalysis in the Methanosarcina thermophila Acetate Kinase

Ingram-Smith, Cheryl; Wharton, Jeffrey; Reinholz, Christian; Doucet, Tara; Hesler, Rachel; Smith, Kerry
Fonte: MDPI Publicador: MDPI
Tipo: Artigo de Revista Científica
Publicado em 12/03/2015 Português
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Acetate kinase (ACK), which catalyzes the reversible phosphorylation of acetate by ATP, is a member of the acetate and sugar kinase/heat shock cognate/actin (ASKHA) superfamily. ASKHA family members share a common core fold that includes an ATPase domain with five structural motifs. The PHOSPHATE1 motif has previously been shown to be important for catalysis. We have investigated the role of two of these motifs in the Methanosarcina thermophila ACK (MtACK) and have shown that residues projecting into the ACK active site from the PHOSPHATE2 and ADENOSINE loops and a third highly conserved loop designated here as LOOP3 play key roles in nucleotide triphosphate (NTP) selection and utilization. Alteration of Asn211 of PHOSPHATE2, Gly239 of LOOP3, and Gly331 of ADENOSINE greatly reduced catalysis. In particular, Gly331, which is highly conserved throughout the ASKHA superfamily, has the greatest effect on substrate selection. Alteration at this site strongly skewed MtACK toward utilization of purines over pyrimidines, unlike the wild type enzyme that shows broad NTP utilization. Further investigation into differences between the ATPase domain in MtACK and other acetate kinases that show different substrate preferences will provide us with a better understanding of the diversity of phosphoryl donor selection in this enzyme family.

Prediction of distal residue participation in enzyme catalysis

Brodkin, Heather R; DeLateur, Nicholas A; Somarowthu, Srinivas; Mills, Caitlyn L; Novak, Walter R; Beuning, Penny J; Ringe, Dagmar; Ondrechen, Mary Jo
Fonte: BlackWell Publishing Ltd Publicador: BlackWell Publishing Ltd
Tipo: Artigo de Revista Científica
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A scoring method for the prediction of catalytically important residues in enzyme structures is presented and used to examine the participation of distal residues in enzyme catalysis. Scores are based on the Partial Order Optimum Likelihood (POOL) machine learning method, using computed electrostatic properties, surface geometric features, and information obtained from the phylogenetic tree as input features. Predictions of distal residue participation in catalysis are compared with experimental kinetics data from the literature on variants of the featured enzymes; some additional kinetics measurements are reported for variants of Pseudomonas putida nitrile hydratase (ppNH) and for Escherichia coli alkaline phosphatase (AP). The multilayer active sites of P. putida nitrile hydratase and of human phosphoglucose isomerase are predicted by the POOL log ZP scores, as is the single-layer active site of P. putida ketosteroid isomerase. The log ZP score cutoff utilized here results in over-prediction of distal residue involvement in E. coli alkaline phosphatase. While fewer experimental data points are available for P. putida mandelate racemase and for human carbonic anhydrase II, the POOL log ZP scores properly predict the previously reported participation of distal residues.

Structural insights into catalysis and dimerization enhanced exonuclease activity of RNase J

Zhao, Ye; Lu, Meihua; Zhang, Hui; Hu, Jing; Zhou, Congli; Xu, Qiang; Ul Hussain Shah, Amir Miraj; Xu, Hong; Wang, Liangyan; Hua, Yuejin
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
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RNase J is a conserved ribonuclease that belongs to the β-CASP family of nucleases. It possesses both endo- and exo-ribonuclease activities, which play a key role in pre-rRNA maturation and mRNA decay. Here we report high-resolution crystal structures of Deinococcus radiodurans RNase J complexed with RNA or uridine 5′-monophosphate in the presence of manganese ions. Biochemical and structural studies revealed that RNase J uses zinc ions for two-metal-ion catalysis. One residue conserved among RNase J orthologues (motif B) forms specific electrostatic interactions with the scissile phosphate of the RNA that is critical for the catalysis and product stabilization. The additional manganese ion, which is coordinated by conserved residues at the dimer interface, is critical for RNase J dimerization and exonuclease activity. The structures may also shed light on the mechanism of RNase J exo- and endonucleolytic activity switch.

Highly Regioselective Indoline Synthesis under Nickel/Photoredox Dual Catalysis

Tasker, Sarah Z.; Jamison, Timothy F.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
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Nickel/photoredox catalysis is used to synthesize indolines in one step from iodoacetanilides and alkenes. Very high regioselectivity for 3-substituted indoline products is obtained for both aliphatic and styrenyl olefins. Mechanistic investigations indicate that oxidation to Ni(III) is necessary to perform the difficult C–N bond-forming reductive elimination, producing a Ni(I) complex which in turn is reduced to Ni(0). This process serves to further demonstrate the utility of photoredox catalysts as controlled single electron transfer agents in multi-oxidation state nickel catalysis.

Heterogeneous catalysis for green chemistry based on nanocrystals

Liu, Yuxi; Zhao, Guofeng; Wang, Dingsheng; Li, Yadong
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica Formato: text/html
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Modern society has an ever-increasing demand for environmentally friendly catalytic processes. Catalysis research is working towards a solution through the development of effective heterogeneous catalysts for environment-related applications. Nanotechnologies have provided effective strategies for the preparation of nanocrystals (NCs) with well-defined sizes, shapes and compositions. Precise control of these NCs provides an important foundation for the studies of structure-performance relationships in catalysis, which is critical to the design of NCs with optimized catalytic performances for practical applications. We focus on recent advances in the development of bottom-up strategies to control NCs structures for some key catalytic applications, including CO oxidation, selective oxidation of alcohols, semihydrogenation of alkynes, and selective hydrogenation of unsaturated aldehydes and nitrobenzene. These key applications have been a popular research focus because of their significance in green chemistry. Herein we also discuss the scientific understandings of the active species and active structures of these systems to gain an insight for rational design of efficient catalytic systems for these catalytic reactions.

I. Stereoselective Construction of Polycyclic Architectures: Enantioselective Catalytic Transannular Ketone-Ene Reactions and an Enantioselective Total Synthesis of (+)-Reserpine II. Synthesis of Chiral Bisthioureas for Anion-Abstraction Catalysis

Rajapaksa, Naomi Samadara
Fonte: Harvard University Publicador: Harvard University
Tipo: Thesis or Dissertation
Português
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The research presented herein explores three aspects of asymmetric catalysis: (1) the development of new catalytic enantioselective reactions, (2) the application of stereoselective catalysis to natural product total synthesis, and (3) the design and synthesis of new chiral catalysts.; Chemistry and Chemical Biology

The Influence of Intramolecular Proton Relays on Catalysis

Graham, Daniel John
Fonte: Harvard University Publicador: Harvard University
Tipo: Thesis or Dissertation; text Formato: application/pdf
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Global energy demand is predicted to increase at an alarming rate over the next century; in order to meet this demand while also limiting the effects of runaway climate change, society will need to shift toward renewable sources of energy. Many of the fundamental chemical transformations that store renewable energy as fuel require the addition or removal of protons. Optimization of catalysts that carry out these transformations can be achieved with proton management at the molecular level. Deliberate construction of molecular catalysts with an intramolecular proton relay is one strategy for controlling the movement of protons during catalysis. These so-called “hangman” catalysts have been shown to increase the rate of catalysis in the cases of hydrogen evolution, oxygen reduction, hydrogen peroxide dismutation, and olefin epoxidation. A new class of hangman porphyrins is now available on the gram scale and can easily be further modified, allowing for unprecedented control the strength and character of pendant proton relays. Using iron complexes of these new hangman porphyrins, the level of control over proton management is demonstrated with the variation in the rates of hydrogen evolution electrocatalysis depending on the nature of the proton relay in the second coordination sphere. Understanding the fundamental electron transfer reactions of reactive oxygen species (ROS) is important in the chemistry of renewable energy storage...

Síntese, caracterização e aplicação de LaSBA-15 e como catalisador para obtenção de biodiesel de soja via rota etílica

Araújo, Larissa Cicianny Luz Ferreira de
Fonte: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Ciência e Engenharia do Petróleo; Pesquisa e Desenvolvimento em Ciência e Engenharia de Petróleo Publicador: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Ciência e Engenharia do Petróleo; Pesquisa e Desenvolvimento em Ciência e Engenharia de Petróleo
Tipo: Dissertação Formato: application/pdf
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Biodiesel is an alternative fuel, renewable, biodegradable and nontoxic. The transesterification of vegetable oils or animal fat with alcohol is most common form of production of this fuel. The procedure for production of biodiesel occurs most commonly through the transesterification reaction in which catalysts are used to accelerate and increase their income and may be basic, acid or enzyme. The use of homogeneous catalysis requires specific conditions and purification steps of the reaction products (alkyl ester and glycerol) and removal of the catalyst at the end of the reaction. As an alternative to improve the yield of the transesterification reaction, minimize the cost of production is that many studies are being conducted with the application of heterogeneous catalysis. The use of nano-structured materials as catalysts in the production of biodiesel is a biofuel alternative for a similar to mineral diesel. Although slower, can esterify transesterified triglycerides and free fatty acids and suffer little influence of water, which may be present in the raw material. This study aimed at the synthesis, characterization and application of nano-structured materials as catalysts in the transesterification reaction of soybean oil to produce biodiesel by ethylic route. The type material containing SBA-15 mesoporous lanthanum embedded within rightly Si / La = 50 was used catalyst. Solid samples were characterized by X-ray diffraction...

Asymmetric hydrogenation of alkenes with cationic iridium(I) complexes of 2-phosphino-1-aminoferrocene ligands

Van Belle, Lori
Fonte: Brock University Publicador: Brock University
Tipo: Electronic Thesis or Dissertation
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Iridium complexes with bidentate P,N ligands represent a class of catalysts that significantly expand the application range of asymmetric hydrogenation. New substrate classes, for which there have previously been no suitable catalysts, can now be efficiently hydrogenated in high conversion and enantioselectivity. These substrates are often of synthetic importance, thus iridium catalysis represents a significant advance in the field of asymmetric catalysis. Planar chiral ferrocenyl aminophosphine ligands in which both heteroatoms were directly bound to the cyclopentadienyl ring were prepared by BF3-activated lithiationsubstitution in the presence of a chiral diamine in 49-59% yield and 75-85% enantiomeric excess. Some of these ligands were recrystallized to enantiomeric purity via ammonium fluoroborate salt formation of the phosphine sulfide. A crystal structure of one of these compounds was obtained and features an intramolecular hydrogen bond between the nitrogen, hydrogen, and sulfur atoms. Neutralization, followed by desulfurization, provided the free ligands in enantiomeric purity. Iridium complexes with these ligands were formed via reaction with [Ir(COD)Clh followed by anion exchange with NaBArF. These complexes were successfully applied in homogeneous hydrogenation of several prochiral substrates...

Transition Metals Catalysis in C-C and C-Heteroatom Bonds Forming Reactions

IAZZETTI, ANTONIA
Fonte: La Sapienza Universidade de Roma Publicador: La Sapienza Universidade de Roma
Tipo: Tese de Doutorado
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Probing the catalytic roles of Arg548 and Gln552 in the carboxyl transferase domain of the rhizobium etli pyruvate carboxylase by site-directed mutagenesis

Duangpan, S.; Jitrapakdee, S.; Adina-Zada, A.; Byrne, L.; Zeczycki, T.; Maurice, M.; Cleland, W.; Wallace, J.; Attwood, P.
Fonte: Amer Chemical Soc Publicador: Amer Chemical Soc
Tipo: Artigo de Revista Científica
Publicado em //2010 Português
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The roles of Arg548 and Gln552 residues in the active site of the carboxyl transferase domain of Rhizobium etli pyruvate carboxylase were investigated using site-directed mutagenesis. Mutation of Arg548 to alanine or glutamine resulted in the destabilization of the quaternary structure of the enzyme, suggesting that this residue has a structural role. Mutations R548K, Q552N, and Q552A resulted in a loss of the ability to catalyze pyruvate carboxylation, biotin-dependent decarboxylation of oxaloacetate, and the exchange of protons between pyruvate and water. These mutants retained the ability to catalyze reactions that occur at the active site of the biotin carboxylase domain, i.e., bicarbonate-dependent ATP cleavage and ADP phosphorylation by carbamoyl phosphate. The effects of oxamate on the catalysis in the biotin carboxylase domain by the R548K and Q552N mutants were similar to those on the catalysis of reactions by the wild-type enzyme. However, the presence of oxamate had no effect on the reactions catalyzed by the Q552A mutant. We propose that Arg548 and Gln552 facilitate the binding of pyruvate and the subsequent transfer of protons between pyruvate and biotin in the partial reaction catalyzed in the active site of the carboxyl transferase domain of Rhizobium etli pyruvate carboxylase.; Saowapa Duangpan...

Acid-base bifunctional periodic mesoporous metal phosphonates for synergistically and heterogeneously catalyzing CO₂ conversion; Acid-base bifunctional periodic mesoporous metal phosphonates for synergistically and heterogeneously catalyzing CO(2) conversion

Ma, T.Y.; Qiao, S.Z.
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
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Integrating multiple functions into one host for improved catalytic performance is challenging and promising for both catalysis and material science. Herein a new acid–base bifunctional periodic mesoporous titanium phosphonate hybrid material is synthesized by a facile one-pot hydrothermal method, using alendronate sodium trihydrate as a coupling molecule. The new material possesses highly periodic mesopores with a large specific surface area of 540 m2 g–1 and pore volume of 0.43 cm3 g–1, favoring the smooth mass transport of reactants and products during the catalytic reaction. It also has an organic–inorganic hybrid framework with homogeneously incorporated phosphonate groups, in which a large number of accessible acidic P–OH and basic −NH2 sites can, respectively, activate aziridine and CO2, synergistically leading to the high conversion (>99%), yield (98%), and regioselectivity (98:2) for the CO2 cycloaddition reaction. The catalytic activity is better than that of the scarcely reported heterogeneous catalysts for aziridine and CO2 cycloaddition and even comparable to that of the state-of-the-art homogeneous ones. Moreover, being superior to the other catalysts, the metal phosphonate materials can be easily separated and reused repeatedly without activity loss...

Development of a Phase Separation Strategy in Macrocyclization Reactions

Bédard, Anne-Catherine
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
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La réaction de macrocyclisation est une transformation fondamentale en chimie organique de synthèse. Le principal défi associcé à la formation de macrocycles est la compétition inhérente avec la réaction d’oligomérisation qui mène à la formation de sousproduits indésirables. De plus, l’utilisation de conditions de dilutions élevées qui sont nécessaires afin d’obtenir une cyclisation “sélective”, sont souvent décourageantes pour les applications à l’échelle industrielle. Malgré cet intérêt pour les macrocycles, la recherche visant à développer des stratégies environnementalement bénignes, qui permettent d’utiliser des concentrations normales pour leur synthèse, sont encore rares. Cette thèse décrit le développement d’une nouvelle approche générale visant à améliorer l’efficacité des réactions de macrocyclisation en utilisant le contrôle des effets de dilution. Une stratégie de “séparation de phase” qui permet de réaliser des réactions à des concentrations plus élevées a été developpée. Elle se base sur un mélange de solvant aggrégé contrôlé par les propriétés du poly(éthylène glycol) (PEG). Des études de tension de surface, spectroscopie UV et tagging chimique ont été réalisées afin d’élucider le mécanisme de “séparation de phase”. Il est proposé que celui-ci fonctionne par diffusion lente du substrat organique vers la phase ou le catalyseur est actif. La nature du polymère co-solvant joue donc un rôle crutial dans le contrôle de l’aggrégation et de la catalyse La stratégie de “séparation de phase” a initiallement été étudiée en utilisant le couplage oxidatif d’alcynes de type Glaser-Hay co-catalysé par un complexe de cuivre et de nickel puis a été transposée à la chimie en flux continu. Elle fut ensuite appliquée à la cycloaddition d’alcynes et d’azotures catalysée par un complexe de cuivre en “batch” ainsi qu’en flux continu.; Macrocyclization is a fundamentally important transformation in organic synthetic chemistry. The main challenge associated with the synthesis of large ring compounds is the competing oligomerization processes that lead to unwanted side-products. Moreover...

Neue polymerfixierte Dirhodium(II)tetracarboxylatkomplexe; New polymer-fixed dirhodium(II)tetracarboxylato complexes

Preschel, Michael
Fonte: Universität Tübingen Publicador: Universität Tübingen
Tipo: Dissertation; info:eu-repo/semantics/doctoralThesis
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Die Arbeit beinhaltet die Darstellung und Anwendung polymergebundener Dirhodium(II)tetracarboxylatkomplexe und vergleicht sie mit den analogen monomeren Komplexverbindungen, welche hervorragend geeignet sind für die selektive Katalyse von Cyclopropanierungsreaktionen von Olefinen mit Diazoverbindungen, sowie als Selektormoleküle in Stationärphasen für die Komplexierungsgaschromatographie. Als Modellverbindung für die Entwicklung der Polymeren diente der von Davies entwickelten Komplex Dirhodium(II)tetrakis[N-(4-tert-butylphenylsulfonyl)prolinat]. Die Eigenschaften der dargestellten Interphasenmaterialien wurden variiert, je nach ihrer nachfolgenden Anwendung in der Katalyse oder der Chromatographie.; This work contains the preparation and application of polymer-bound dirhodium(II)tetracarboxylato complexes and compares it to the monomeric complexes, which are appropriate compounds for the selective catalysis of cyclopropanation reactions of olefins with diazo compounds and also as selector molecules in stationary phases for complexation gas chromatography. Davies' complex tetrakis[N-(4-tert-butylphenylsulfonyl)prolinato] dirhodium(II) was used as a model for the development of the polymers. Depending on the application in catalysis or chromatography the characteristics of the prepared interphase materials were varied.

Redoxaktive metallorganische Iridium- und Ruthenium-Komplexkatalysatoren in Interphasen - elektrochemische und spektroskopische Charakterisierung; Redox active organometallic Ir and Ru catalysts in interphases - electrochemical and spectroscopic characterization

Novak, Filip
Fonte: Universität Tübingen Publicador: Universität Tübingen
Tipo: Dissertation; info:eu-repo/semantics/doctoralThesis
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In dieser Arbeit wurden drei sehr unterschiedlichen redoxaktiven Systeme in Zusammenhang mit der Katalyse in Interphasen untersucht: (i) Ir-PCP-Komplexe, (ii) immobilisierte Ru(II)-diamin-Komplexe und (iii) Kieselgelnanopartikel nach Stöber modifiziert mit Fc- und Ru(II)-Spezies. Um elektronische sowie strukturelle Eigenschaften dieser Systeme bestimmen, wurden verschiedene elektroanalytische (CV, EQCN) sowie spektroskopische Methoden (NMR, UV-VIS, AAS, ICP-MS, SEM) eingesetzt. Die Redoxeigenschaften der Ir-PCP-Komplexe wurden in Lösung mit Hilfe der Cyclovoltammetrie bestimmt. Obwohl die Strukturen der Komplexe sehr ähnlich sind, zeigt das voltammetrische Verhalten unterschiedliche elektrochemische Eigenschaften. Die Redoxmechanismen der Komplex basieren auf einen Elektronentransfer Ir(III) zu Ir(IV), wobei eine intramolekulare C-H-Aktivierung stattfinden kann. Diese C-H-Aktivierung führt zu einer intramolekulare Dehydrierung der Ir-PCP-Komplexe. Die Computersimulationen bestätigten, dass eine solche Dehydrierung nach dem Elektronentransfer Ir(III)/Ir(IV) thermodynamisch günstiger verläuft. Die Ergebnisse der elektrochemischen Untersuchung wurden auch durch NMR-Experimente mit einem Oxidationsmittel (TBPA) sowie einem Substrat (Cyclooctan) bestätigt. Um weitere katalytisch aktive Systeme zu charakterisieren...

Stereoselective synthesis of substituted hexahydro-3a,4a-diazacyclopentaphenanthren-4-ones and aminoferrocenes

Zaifman, Joshua David
Fonte: Brock University Publicador: Brock University
Tipo: Electronic Thesis or Dissertation
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This thesis explored the development of several methodologies for the stereoselective construction of ligand frameworks and some of their applications. The first segment concerns the application of an enantioselective lithiation at an Sp3_ hybridized position adjacent to nitrogen by means of the widely used and typically highly effective enantioselective lithiation with ( -)-sparteine. This investigation was intended to develop a method to install chirality into a system that would be converted into a family of diaminoylidenes for use as phosphine mimics in transition metal catalysis or as nucleophilic reagents. Molecular modeling of the system revealed some key interactions between the substrate and (-)-sparteine that provided general insight into the diamine's mode of action and should lend some predictive value to its future applications. The second portion focuses on the development of methods to access 1,2- disubstituted aminoferrocenes, an underexplored class of metallocenes possessing planar chirality. Two routes were examined involving a diastereoselective and an enantioselective pathway, where the latter method made use of the first BF3-mediated lithiation-substitution to install planar chirality. Key derivatives such as 1...

Utilisation du motif imidazole en transport d'anions et en catalyse organométallique

Charbonneau, Mathieu
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
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Le motif imidazole, un hétérocycle à 5 atomes contenant 2 atomes d’azote et trois atomes de carbone, présente des propriétés physico-chimiques intéressantes qui en font un composé de choix pour plusieurs applications. Parmi ces propriétés, la fonctionnalisation simple des deux atomes d’azote pour former un sel d’imidazolium est très intéressante. Ces sels sont d’excellents précurseurs de carbènes N-hétérocycliques (NHC) et sont couramment utilisés pour synthétiser des ligands en vue d’une utilisation en catalyse organométallique. D’autre part, cette famille de composés possède des propriétés anionophores permettant une utilisation en transport anionique. Le présent travail contient les résultats de travaux concernant ces deux domaines, soit la catalyse et le transport anionique. Dans un premier temps, les propriétés de dérivés de l’imidazole sont exploitées pour former un catalyseur de type palladium-NHC qui est utilisé pour catalyser la réaction de Suzuki-Miyaura en milieu aqueux. L’efficacité de ce catalyseur a été démontrée en utilisant aussi peu que 0,001 mol% pour un rendement quantitatif. Il s’agit de la première occurrence d’un processus hétérogène et recyclable dans l’eau...