• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 22
  • 11
  • 4
  • 4
  • 2
  • 2
  • 1
  • 1
  • Tagged with
  • 65
  • 20
  • 13
  • 12
  • 12
  • 10
  • 9
  • 8
  • 7
  • 6
  • 6
  • 6
  • 5
  • 5
  • 5
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Modified nucleosides and oligonucleotides as ligands for asymmetric reactions

Nuzzolo, Marzia January 2010 (has links)
Development of chiral ligands capable of achieving high selectivity for various asymmetric catalytic reactions has been an important aim of both academia and industry. Nature is capable to selectively catalyze chemical reactions by using enzymes. An ideal catalyst would combine the selectivity of nature and the reactivity of man-made catalysts based on transition metal complexes. The two biomolecules chosen to achieve this are DNA and PNA. DNA is a chiral molecule with high binding selectivity towards small molecules and has been used as ligand for asymmetric catalysis. PNA is an achiral structural analogue of DNA that can form duplexes with DNA. To produce DNA based catalysts it is necessary to introduce a ligand such as a phosphine that will strongly coordinate to transition metals. To achieve this, functionalized linkers need to be introduced into a DNA strand, to covalently couple the phosphine moiety at a specific location of the DNA strand. Amine linkers and several modified nucleosides have been prepared containing thiol and amine functionalities and some of them were successfully introduced into DNA strands to function as linkers for the introduction of phosphine functionalities. Those strands were purified and an adequate procedure was developed for their analysis by MALDI-TOF. Diphenylphosphino carboxylic acids have been coupled to amine modified deoxyuridines by amide bond formation. The same coupling method has been used for oligonucleotides. DNA strands containing phosphine moieties were characterized by MALDI-TOF and ³¹P NMR spectrometry. ³¹P NMR spectroscopy was also used to confirm coordination of a phosphine modified 15-mer to [PdCl(η³-allyl)]₂. The phosphine modified nucleobases were also tested as ligands for palladium catalyzed allylic alkylation and allylic amination with diphenylallyl acetate as substrate although no enantioselectivity was observed. A PNA monomer was also modified with a bidentate sulfur protected phosphine and successfully introduced into a short PNA strand using manual solid phase synthesis. This strand was analyzed by MALDI-TOF. Moreover, preliminary studies were performed to test the use of aptamers as scaffolds for targets containing a ligand functionality.
52

Homologické ferrocenové fosfiny / Homologous ferrocene phosphines

Vosáhlo, Petr January 2018 (has links)
Title: Homologous ferrocene phosphines Author: Bc. Petr Vosáhlo Department: Department of Inorganic Chemistry Supervisor: prof. RNDr. Petr Štěpnička, Ph.D., DSc. Abstract: This thesis describes the synthesis and coordination behaviour of ferrocene diphosphines derived from 1,1'-bis(diphenylphosphino)ferrocene (dppf). Dppf is one of the most succesful ferrocene ligands, which can be used in various metal-catalyzed reactions. This study aimed to prepare analogous ligands with one dialkylphosphino substituent and one (diphenylphosphino)methyl group. These ligands were oxidized by KSeCN to afford the corresponding phosphinoselenides. The phosphinoselenides were used to assess sigma-donor abilities by measuring the coupling constant 1 JSeP via 31 P NMR spectroscopy. Lastly, the coordination behaviour of these ligands in palladium complexes was studied. The homologous ligands usually formed a mixtures containing a chelate complex and dimeric species with trans- coordinated ligands. Key words: ferrocene, phosphines, homologous ligands, palladium(II) complexes, structure elucidation.
53

Synthesis of 1,3,5-triaza-7-phosphaadamantane (PTA) and 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane (DAPTA) complexes and the development of chromium salen catalysts for the copolymerization of CO2 and epoxides

Ortiz, Cesar Gabriel 30 September 2004 (has links)
Two main areas are considered in this manuscript. The first describes the synthesis of group 10 metal complexes incorporating the water-soluble 1,3,5-triaza-7-phosphaadamantane (PTA) ligand and the second deals with the preparation of Cr(salen)X catalysts for the copolymerization of CO2 and epoxides. In the first topic, the synthesis of nickel(II) and palladium(II) salicylaldiminato complexes incorporating PTA has been achieved employing two preparative routes. Upon reacting the original ethylene polymerization catalyst developed by Grubbs and coworkers (Organometallics, 1998, 17, 3149), (salicylaldiminato)Ni(Ph)PPh3, with PTA using a homogeneous methanol/toluene solvent system resulted in the formation of the PTA analogs in good yields. Alternatively, complexes of this type may be synthesized via a direct approach utilizing (TMEDA)M(CH3)2 (M = Ni, Pd), the corresponding salicylaldimine, and PTA. Polymerization reactions were attempted using the nickel-PTA complexes in a biphasic toluene/water mixture in an effort to initiate ethylene polymerization by trapping the dissociated phosphine ligand in the water layer, thereby, eliminating the need for a phosphine scavenger. Unfortunately, because of the strong binding ability of the small, donating phosphine (PTA) as compared to PPh3, dissociation did not occur at a temperature where the complexes are not subjected to decomposition. Additionally, the unexplored PTA derivative, 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane (DAPTA), prepared by the literature procedure, was fully characterized by NMR and X-ray analysis. DAPTA is found be similar to its parent (PTA) in coordination mode and binding strength, as supported by its representative group 6 and group 10 complexes The second main topic involves the copolymerization of CO2 and epoxides (i.e., cyclohexene oxide (CHO)) for the formation of polycarbonate using Cr(salen)X (X = Br, OPh) catalysts with one equivalent of PR3 as the co-catalyst. The use of these catalysts and cocatalysts results in the most active chromium-based catalytic systems to date. The . hr-1highest activities observed are on the order of 109 mol CHO consumed . mol Cr-1 using PCy3 as the co-catalyst, and is clearly seen in the in situ monitoring of copolymer formation. An advantage of these systems involves the lack of cyclic carbonate production and high CO2 incorporation (>99%) within the polymer.
54

Application of the metal-catalyzed rearrangement of propargyl acetates to the total synthesis of natural products of the neomerane family : application in catalysis of new secondary phosphine oxide- and NHC-capped cyclodextrin-gold(I) complexes / Application du réarrangement métallo-catalysé des acétates propargyliques à la synthèse totale de produits naturels de la famille des néoméranes : application en catalyse de nouveaux complexes d’or(I) à base d’oxides de phosphines secondaires et de cyclodextrines

Tugny, Coralie 13 November 2015 (has links)
L'étude des petites molécules naturelles apporte continuellement de nouvelles connaissances en chimie organique et a un impact certain sur la recherche biomédicale. Les réactions catalysées par des métaux de transition ont fréquemment été utilisées dans des étapes clés vers la synthèse de produits naturels. En particulier au cours de la dernière décennie, l'or a été de plus en plus utilisé en catalyse homogène pour effectuer ces transformations. Le présent travail a pour objectif la valorisation en synthèse totale du réarrangement des acétates propargyliques catalysé par l'or. La (±)-Valénéomérine B et le (±)-Néoméranol sont deux produits naturels de la famille des Néoméranes dont nous avons envisagé la synthèse via la préparation d'un intermédiaire commun issu du réarrangement d'un acétate propargylique catalysé à l'or. Parallèlement, le comportement de nouveaux complexes d'or(I) à base d'oxides de phosphines secondaires et de cyclodextrines a été étudié dans le but de mieux contrôler la sélectivité des réactions catalysées à l'or. / The study of small molecule natural products provides some knowledge about organic chemistry and has an impact on biomedical research. Transition metal-catalyzed reactions have been frequently used to affect key transformations. Especially, there has been a noticeable trend during the past decade towards the use of homogeneous gold-catalyzed transformations. This work aims at the valorization of the gold-catalyzed rearrangement of propargyl acetates in the total syntheses of (±)-Valeneomerin B and (±)-Neomeranol. These compounds are sequiterpenoid natural products, the synthesis of which has been envisioned from the preparation of a common intermediate resulting from the gold-catalyzed rearrangement of a propargyl acetate precursor. At the same time, the behaviour of new secondary phosphine oxide- and CNHC-capped cyclodextrin-gold(I) complexes has been studied, to try and achieve better control on the course of gold-catalyzed transformations.
55

Catalytic systems adapted to glycerol medium : applications in selective processes / Systèmes catalytiques adaptés au glycérol : applications dans des processus sélectifs

Rodriguez Rodriguez, Marta 27 January 2017 (has links)
La grande quantité des solvants utilisés dans l'industrie chimique représente un des problèmes les plus importants à aborder, d'un point de vue environnemental ainsi qu'économique. Les solvants communément utilisés sont volatiles, toxiques, inflammables et/ou corrosifs, et leur substitution par des autres moins nocifs est un objectif primordiale dans un cadre de développement durable. Le glycérol se présente comme un candidat prometteur pour remplacer les solvants organiques conventionnels. Il est généré comme produit concomitant dans la production de biodiesel. En conséquence, la valorisation du glycérol est devenue un enjeu majeur. Ce composé possède des propriétés très intéressantes pour être utilisé comme solvant en catalyse, telles que son innocuité, haut point d'ébullition, pression de vapeur négligeable, capacité de solubilisation de composés organiques et inorganiques, faible miscibilité avec autres solvants organiques et également son faible coût. Cette Thèse à pour objectif développer des nouveaux systèmes catalytiques dans un milieu glycérol. En particulier, dans ce travail nous montrons comme le glycérol promue la stabilisation de nanoparticules de cuivre (I) capables de catalyser la réaction de Huisgen 1,3-dipolaire entre alcynes terminaux et azotures organiques (connu comme la réaction click), de façon très efficace à température ambiante. Dans ce solvant, cette réaction peut aussi être réalisée en absence de cuivre avec alcynes internes non activés, en travaillant sous activation microondes. L'utilisation du glycérol favorise la réaction par rapport à des autres solvants (incluant ceux qui sont protiques), probablement grâce à sa capacité pour former liaisons d'hydrogène, favorisant l'interaction avec l'irradiation microondes (et ainsi accélérant la réaction). Avec le propos d'étudier des transformations stéréosélectives, nous avons préparé des nouveaux ligands énantiopures dérivés du PTA (1,3,5-triaza-7-phosphaadamantane). Ces composés innovants ont été utilisés en réactions énantiosélectives comme l'addition asymétrique de B2pin2 à N-Boc-imines (Cu) ou encore la alpha-amination (Cu), ou encore comme organocatalyseur (réaction de Morita-Baylis- Hillman). / Solvents are used in huge amounts in the chemical industry and this is one of the biggest problems to be solved not only from an environmental point of view, but also for economic reasons. The solvents commonly used in the industry are volatile, toxic, inflammable and/or corrosive; then, their replacement by others less harmful represents a crucial objective. Glycerol appears as a promising candidate to substitute the conventional organic solvents. It is produced in huge amounts as a waste in biodiesel industry. Consequently, the valorisation of glycerol becomes an important concern. This compound possesses very interesting properties to be used as solvent such as its non-toxicity, the wide range of temperature for its liquid state, negligible vapour pressure, capacity for solubilising organic and inorganic compounds, low miscibility with other organic solvents and also its low price. This Thesis deals with the development of new catalytic systems in glycerol medium. In particular, in this work we show how glycerol can facilitate the stabilisation of copper(I) nanoparticles that are able to catalyse the 1,3-dipolar Huisgen cycloaddition between terminal alkynes and organic azides (known as click reaction). The reaction proceeds at room temperature and it is very efficient. Moreover, this reaction can be carried out in the absence of copper using non-activated internal alkynes, working under microwave irradiation. Glycerol favours the process in comparison with other solvents (including protic ones), probably due to its ability to form hydrogen bonds, which favours the interaction with the microwave irradiation (accelerating the process). With the aim of studying stereoselective transformations, we have conceived new enantiopure ligands derived from PTA (1,3,5-triaza-7-phosphaadamantane). These innovative phosphines have been applied in enantioselective processes, such as pinacolboryl addition to N-Boc-imines (Cu) or alpha-amination (Cu), among others, or as organocatalyst (Morita-Baylis-Hillman reaction).
56

Applications of functionnal diphosphines quinonoid zwietterions to coordination chemistry and surface functionalization / Applications de ligands diphosphines fonctionnelles et de zwitterions quinonoïdes à la chimie de coordination et à la fonctionalisation de surfaces

Ghisolfi, Alessio 20 June 2014 (has links)
Le but de ce travail de thèse était de développer de nouvelles familles de ligands polyfonctionnels pour étudier, dans un premier temps, leur chimie de coordination vis-à-vis de métaux de transition et, dans un second temps, en fonction des espèces formées, leurs propriétés physiques (magnétiques par exemple) et/ou catalytiques. L’évaluation de leur potentiel pour la formation de nouveaux matériaux ou la fonctionnalisation de supports métalliques faisait également partie intégrante des objectifs de cette thèse. De ce fait, chaque ligand a été fonctionnalisé avec des groupements adaptés à l’ancrage sur surfaces, comme des fonctions zwitterioniques ou des thio-éthers. / The aim of this thesis was to develop new families of polyfunctional ligands to study their coordination chemistry towards transition metals and, depending on the products formed, to investigate their physical (e.g. magnetic) and / or catalytic properties. The evaluation of their potential for the formation of new materials as well as for the functionalization of metal surfaces was also part of the objective of this thesis. Therefore, each ligand has been functionalized with groups suitable for the anchoring on metallic surfaces, such as zwitterionic or thioethers moieties.
57

Imino esters as useful precursors for the synthesis of glutamate derivatives and functionalization of carbon materials

Rodríguez-Flórez, Lesly V. 27 May 2024 (has links)
The present doctoral thesis focused mainly on the use of α-imino esters in 1,4-conjugated addition reactions (Michael-type additions) which have been optimized using phosphines acting as organocatalysts. On the other hand, α-imino esters have been evaluated in heterogeneous systems functionalizing carbonaceous matrices through 1,3-dipolar cycloaddition reactions and their subsequent application in catalysis. Chapter 1 describes a new approach for the preparation of glutamates and pyroglutamates surrogates without the use of bases, through Michael-type addition reactions between different imino esters and conjugated alkenes in the presence of a phosphine that acts as an organocatalyst. Chapter 2 reports the results obtained from the functionalization of single-walled nanotubes (SWCNT) with different imino esters through the microwave-assisted 1,3-dipolar cycloaddition reaction; the pyrrolidine rings-functionalized material was characterized by using several techniques and subsequently the synthesis of a heterogeneous catalyst using an iridium complex was afforded. This supported catalyst was evaluated, as a proof of concept, in the hydrogen-transfer reaction of acetophenone to yield 1-phenyletanol. In Chapter 3 the covalent functionalization of multilayer graphene (MLG) via microwave-assisted 1,3-dipolar cycloaddition with azomethine ylides generated by thermal 1,2-prototropy from various imino esters is described. In particular, this strategy allows to anchor an imino ester containing a 2,2’-bipyridine unit in order to obtain a functionalized material capable of assembling a ruthenium atom to achieve a heterogeneous supported complex. This new catalyst was tested, as a proof of concept, in the photocatalytic aerobic oxidative hydroxylation reaction of 4-methoxyphenylboronic acid. / The present work has been possible thanks to the Spanish Ministerio de Ciencia, Innovación y Universidades (project RED2018-102387-T) the Spanish Ministerio de Economía, Industria y Competitividad, Agencia Estatal de Investigación (AEI) (MCIN/AEI/10.13039/501100011033) and Fondo Europeo de Desarrollo Regional (FEDER, EU) (projects CTQ2017-82935-P, PID2019-107268GB-I00 and PID2021-123079OB-I00), the Generalitat Valenciana (IDIFEDER/2021/013, GVACOVID19/2021/079 and CIDEGENT/2020/058), Medalchemy S. L. (Medalchemy-18T) and the University of Alicante (VIGROB-068, UAUSTI21-05). Additionally, I would like to thanks the Generalitat Valenciana for the Grisolía’s fellowship (GRISOLIAP/2020/111) from the Santiago Grisolía program and for the CIBEFP/2022/17 grant to carry out a three-months research stay in the Department of chemical and pharmaceutical sciences at the University of Trieste-Italy.
58

Supramolecular studies with functionalised group 15 ligands

Sanchez-Ballester, Noelia M. January 2010 (has links)
This thesis has been divided into five sections. The first chapter introduces the main themes of this thesis, including the description of the concepts of supramolecular chemistry, crystal engineering, hydrogen bonding and graph set analysis. The final section of chapter one describes a typical X-ray experiment used to determine the structures of the compounds presented in this thesis. Chapter two describes the synthesis and single crystal structures of copper(I) complexes with pyridine- and pyrazine-carboxylic acids. A series of novel solvent inclusion compounds of copper(I) complexes with pyridine- and pyrazine-carboxylic acids and the hydrogen bonding patterns adopted are also discussed. Chapter three reports the potential uses of boronic acids as building blocks for the design of novel solid-state architectures utilising hydrogen bonds. Novel copper(I) pyridine-/pyrazine-carboxylate complexes with boronic acid co-crystals are presented in which the heterodimeric boronic carboxylate R22(8) ring motif is present in all cases. Chapter four discusses the synthesis of novel ditertiary phosphines bearing functional groups with hydrogen bonding potential either via a three-step or single step synthetic route which involves a well known method of reductive amination followed by an efficient Mannich-based condensation. Complexation studies of these P,P-bidentate ligands with various transition metal centres such as Pt(II), Mo(0), Ru(II) and Au(I) are also presented. The effect on the structural motifs observed in these series of compounds by the regioselective incorporation of functional groups with potential hydrogen bonding capability such as hydroxyl and amide is also given. Finally, chapter five contains the synthesis and coordination studies of new phosphorus donor ligands leading to ideas for further work.
59

Synthèse de mono et diphosphines dérivées d'amino acides ou de peptides, appliquées en chimie de coordination et pour le greffage de fullerène C60 / Synthesis of mono and diphosphine amino acid and peptides derivative applied for coordination chemistry and grafting fullerene

Minois, Pauline 18 December 2013 (has links)
La synthèse de phosphines secondaires borane dérivées d’aminoacides ou de dipeptides, et leur application pour la préparation de ligands ou le greffage du fullerène, est décrite. Elle se fait sans racémisation avec des rendements atteignant 98%, par alkylation de phosphines borane primaires avec un dérivé γ-iodo aminoacide, dans les conditions de transfert de phase. Les diphosphines tertiaires dérivées d’aminoacides, obtenues après une seconde alkylation avec des rendements atteignant 70%, sont parmi les premiers exemples de diphosphines greffées par une liaison P-C sur la chaine latérale d’un aminoacide. Les mono et diphosphines dérivées d’aminoacides ont été testées en catalyse d’allylation ou d’hydrogénation asymétriques catalysées par des complexes de palladium ou de rhodium. D’un autre côté, un complexe de cis platine a été préparé à partir d'une diphosphine dérivée d'un aminoester. Ses propriétés cytotoxiques ont été testées sur des lignées cellulaires ovariennes cancéreuses A2780. Dans une seconde partie les phosphines secondaires borane d’aminoacides et de peptides ont été utilisées pour le greffage du fullerène, par hydrophosphination en transfert de phase. L’étude électrochimique du dérivé fullerène d’aminoester de benzyle, a permis d’établir que ce composé se décomposait par électrolyse, avec coupure de la liaison P-C, pour libérer le fullerène et la phosphine secondaire borane aminoester. Ces travaux ouvrent de nouvelles perspectives pour la chimie des dérivés phosphines ou fullerène d'aminoacides et de peptides. / The synthesis of secondary phosphine borane amino acids or dipeptides and their applications for the preparation of chiral ligands or for the grafting of fullerene, is described. These compounds were synthesized in good yield (up to 98%) without racemization. The principle of the synthesis is based on the alkylation of primary phosphine borane with a γ-iodo amino acid using phase transfer conditions. Tertiary diphosphine amino acids are obtained with 70% yield after a second alkylation. These compounds are one of the first examples of diphosphine grafted with a P-C bond on the side chain of amino acid. First of all, mono and diphosphine amino acid derivatives were used in asymmetric allylic substitution with palladium precursor or in asymmetric hydrogenation with rhodium precursor. In another hand, a cis platinum complex was synthesized with 60% yield from the diphosphine amino acid derivative. The cytotoxic properties of this complex were tested against human ovarian carcinogenic cell lines A2780. In the second part, the secondary phosphine borane amino acids and peptides have been used for grafting fullerene C60 by hydrophosphination using phase transfer conditions. The electrochemical study of the fullerene amino benzyl ester derivative has shown the cleavage of the P-C60 bond by electrolysis, affording the free fullerene and the secondary phosphine borane amino ester moiety. This work opens new perspectives for the chemistry of fullerene and phosphine derivatives of amino acids and peptides.
60

Fosfinoferrocenové amidy a hydrazidy / Phosphinoferrocene amides and hydrazides

Solařová, Hana January 2011 (has links)
Title: Phosphinoferrocene amides and hydrazides Author: Hana Solařová Department: Department of Inorganic Chemistry Supervisor: doc. RNDr. Petr Štěpnička, Ph.D. Abstract: While studying functionalized phosphinoferrocene ligands, we recently turned to phosphinoferrocene carboxamides. These donors already proved to be versatile ligands for coordination chemistry and catalysis. This led us to synthesize and study the archetypal representative, 1'-(diphenylphosphino)-1-carbamoylferrocene (5), and the corresponding hydrazide 6. PPh2 COOH Fe Hdpf PPh2 CONH2 Fe 5 PPh2 CONHNH2 Fe 6 This work describes the preparation of primary amide 5 and hydrazide 6 from 1'- (diphenylphosphino)-1-ferrocenecarboxylic acid (Hdpf) via the corresponding acylbenzo- triazole derivative. The hydrazide was alternatively obtained from Hdpf methylester and hydrazine hydrate. Both newly synthesized compounds were characterized by spectroscopic methods (NMR, IR, and MS) and elemental analysis, and their crystal structures were determined by single-crystal X-ray crystallography. The amide was further utilized in the preparation of several palladium complexes, which were characterized in a similar manner including X-ray crystallography. One palladium complex was obtained also from the hydrazide. However, the hydrazide was used mainly as a...

Page generated in 0.0709 seconds