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Showing 131 to 140 of 146 (0.028 seconds)| 131 |
NHC portant des azotures : intermédiaires dans la synthèse catalysée d‘hétérocycles polyazotés et auto-fonctionnalisation de complexes métal-NHC / Azide tagged NHC : intermediates in the catalysed synthesis of nitrogen rich heterocycles and auto-functionalization of metal-NHC complexesFauché, Kévin 13 December 2018 (has links)
Les carbènes N-hétérocycliques (NHC) sont très utilisés pour complexer les métaux de transition. Ils quittent rarement ce rôle de ligand ancillaire et trouvent, depuis une vingtaine d’années, des applications en catalyse ou, plus récemment, en chimie médicinale. Dans ce travail, nous discuterons d’une méthode de synthèse douce conduisant à la formation de complexes AgI – NHC via une source d’argent soluble. Cette méthode nous a permis d’obtenir des complexes bien connus mais également d’accéder à une nouvelle série de complexes NHC-Ag-phosphine. Nous présenterons également une nouvelle réaction où des NHC portant une fonction azoture à proximité du carbone du carbène quittent leur rôle de ligand ancillaire et conduisent à la formation d’hétérocycles azotés par cyclisation carbène-nitrène. Cette réaction sera présentée en détail, ainsi que la caractérisation spectroscopique concernant une sous-série de composés fluorescents obtenus par cette méthode. Enfin, nous présenterons une stratégie de post-fonctionnalisation de complexes développée dans notre équipe. Des complexes argent(I)-NHC portant un azoture proches du centre carbénique catalysent leur propre fonctionnalisation. De plus, des complexes de cuivre(I) portant des azotures en position éloignée du centre métallique seront greffés sur des nanoparticules magnétiques pour servir de catalyseur recyclables. / N-heterocyclic carbenes (NHC) are widely used to complex transition metals. They rarely leave their role as ancillary ligand and find, since 20 years, applications in catalysis or, more recently, in medicinal chemistry. In this work, we will discuss a mild synthetic method leading to the formation of AgI – NHC complexes via a soluble silver species. This method allowed us to obtain well known complexes but also to access a new series of NHC-Ag-phosphine complexes. We will also present a new reaction where NHC ligands bearing an azide function close to the carbenic center leave their role as ancillary ligand and lead to the formation of nitrogen rich heterocycles by a carbene-nitrene cyclization. This reaction will be presented in detail, along with the spectroscopic characterization regarding a sub-series of fluorescent compounds obtained by this method. Finally, we will present a post-functionalization strategy of complexes developed in our team. Silver(I)-NHC complexes tagged by an azide close to the carbenic center catalysed their own functionalization. Moreover, copper(I) complexes tagged by an azide function in a distant position from the metallic centre will be grafted on magnetic nanoparticles to act as recyclable catalysts.
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Synthesis and Reactions of α-Azido AlcoholsFirdous, Samia 13 April 2012 (has links) (PDF)
Die vorliegende Arbeit beschäftigt sich mit der Untersuchung von a-Azidoalkoholen, welche über die Reaktion von aliphatischen sowie aromatischen Aldehyden mit HN3 leicht zugänglich sind und die im Gleichgewicht mit den jeweiligen Ausgangsstoffen vorliegen. Bei Raumtemperatur stellt sich dieses Gleichgewicht sehr schnell ein und man erhält spezifische Konzentrationen an Eduktaldehyd, Stickstoffwasserstoffsäure und a-Azidoalkohol. Die Reaktion von Aldehyden mit HN3 generiert dabei ein neues Chriralitätszentrum, wodurch die Umsetzung chiraler Aldehyde, wie z. B. von Zuckerderivaten, zwei anomere Produkte hervorbringt.
Die erstmalig erfolgreichen Synthesen zur Erzeugung von 4-Brom-4-methylpentanal sowie 4-Azido-4-methylpentanal werden ebenfalls beschrieben. Letztere Verbindung reagiert dabei ebenso wenig via einer intramolekularen 1,3-dipolaren Cycloaddition zum entsprechenden 4,5-Dihydro-1,2,3,4-oxatriazol-Derivat wie das analoge-Azidobutanal, was im Gegensatz zu Literaturangaben steht.
Des Weiteren werden einige interessante Reaktionen der a-Azidoalkohole untersucht. Die Oxidation mit Pyridiniumchlorochromat (PCC) bei –60°C führt zu Carbonylaziden. Die Photolyse bei –50°C generiert unter Stickstofffreisetzung Nitrene, welche mittels Wasserstoffwanderung und anschließender Tautomerisierung des resultierenden Intermediats zu Säureamiden umlagern. Die ebenfalls mögliche 1,2-Wanderung einer Gruppe R in a-Position führt dabei zu einem Intermediat, aus welchem sofort das entsprechende Formamid-Derivat entsteht. a-Azidoalkohole reagieren mit PBr3 in einer sauberen Reaktion durch die Substitution der Hydroxylfunktion unter Bildung der jeweiligen 1-Azido-1-brom-Verbindung. / In this work, α-azido alcohols which exist in equilibrium with the starting materials have been studied by the reactions of aliphatic and aromatic aldehydes with HN3. In some cases the title compounds can be isolated from the mixture at low temperature. At room temperature, however, the equilibrium is fast and there are again specific concentrations of the aldehyde, hydrazoic acid, and the α-azido alcohol. The reaction of aldehydes with HN3 creates a new chiral center and a chiral aldehyde, e.g. sugar derivatives, produces two anomeric products.
The first procedures to prepare 4-bromo-4-methylpentanal and 4-azido-4-methylpentanal are also reported. The latter compound and also the parent 4-azidobutanal do not lead to 4,5-dihydro-1,2,3,4-oxatriazoles by intramolecular 1,3-dipolar cycloaddition, although it was claimed in the literature.
Furthermore, some interesting reactions of the α-azido alcohols have been investigated. The oxidation of α-azido alcohols with pyridinium chlorochromate (PCC) at −60 °C leads to formation of carbonyl azides. The photolysis of α-azido alcohols at −50 °C generates nitrenes with liberation of dinitrogen, which lead to the formation of acid amides after the migration of hydrogen and subsequent tautomerism of the intermediate. 1,2-Migration of a group R in the α-position can produce an intermediate stage which is rapidly converted into formamide derivative. α-Azido alcohols react with PBr3 to give 1-azido-1-bromo derivatives in a clean reaction by substitution of hydroxyl group at the α-position.
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Estudo da reação de modificação do poli(cloreto de vinila) com nucleófilos nitrogenados e das aplicações como suporte em reações de acoplamento / Study the reaction of modification of poly(vinyl chloride) with nitrogen nucleophiles and applications as substrates for coupling reactionsPâmella Santos de Souza 23 March 2015 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Neste trabalho foi realizada a modificação química do poli(cloreto de vinila) (PVC) pela sua reação com azida de sódio, onde alguns dos seus átomos de cloro foram substituídos por azidas. Em seguida o grupo incorporado foi transformado em triazóis por uma reação de cicloadição 1,3 entre o polímero modificado e propiolato de etila, sendo a reação catalisada por iodeto de cobre. Essas reações foram conduzidas sob aquecimento convencional e empregando irradiação de micro-ondas. Inicialmente, a reação incorporou 20% de triazol no PVC, sendo avaliadas as condições reacionais ideais. Essas condições foram usadas para a formação de novos copolímeros com diferentes teores de triazóis incorporados. Os produtos obtidos foram usados para o suporte de paládio que é utilizado como catalisador na reação de Suzuki-Miyaura. Todos os copolímeros foram caracterizados por espectroscopia na região do infravermelho com transformada de Fourier (FTIR) / In this work was performed the chemical modification of poly(vinyl chloride) (PVC) by its reaction with sodium azide, in which some of their chlorine atoms has been replaced with azides. Then the azide group was converted to 1,2,3-triazoles by a 1,3-cycloaddition reaction between the modified polymer and ethyl propiolate, the reaction was catalyzed by copper iodide. These reactions were conducted using conventional heating and microwave irradiation. Initially, the reaction incorporated triazole in 20% of PVC, the optimal reaction conditions was evaluated. These conditions were used for the formation of new copolymers with different amounts of incorporated triazoles. The products obtained were used as a support for palladium, which is used as a catalyst in Suzuki-Miyaura reaction. All copolymers were characterized by infrared spectroscopy, Fourier transform spectroscopy (FTIR)
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Estudo da reação de modificação do poli(cloreto de vinila) com nucleófilos nitrogenados e das aplicações como suporte em reações de acoplamento / Study the reaction of modification of poly(vinyl chloride) with nitrogen nucleophiles and applications as substrates for coupling reactionsPâmella Santos de Souza 23 March 2015 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Neste trabalho foi realizada a modificação química do poli(cloreto de vinila) (PVC) pela sua reação com azida de sódio, onde alguns dos seus átomos de cloro foram substituídos por azidas. Em seguida o grupo incorporado foi transformado em triazóis por uma reação de cicloadição 1,3 entre o polímero modificado e propiolato de etila, sendo a reação catalisada por iodeto de cobre. Essas reações foram conduzidas sob aquecimento convencional e empregando irradiação de micro-ondas. Inicialmente, a reação incorporou 20% de triazol no PVC, sendo avaliadas as condições reacionais ideais. Essas condições foram usadas para a formação de novos copolímeros com diferentes teores de triazóis incorporados. Os produtos obtidos foram usados para o suporte de paládio que é utilizado como catalisador na reação de Suzuki-Miyaura. Todos os copolímeros foram caracterizados por espectroscopia na região do infravermelho com transformada de Fourier (FTIR) / In this work was performed the chemical modification of poly(vinyl chloride) (PVC) by its reaction with sodium azide, in which some of their chlorine atoms has been replaced with azides. Then the azide group was converted to 1,2,3-triazoles by a 1,3-cycloaddition reaction between the modified polymer and ethyl propiolate, the reaction was catalyzed by copper iodide. These reactions were conducted using conventional heating and microwave irradiation. Initially, the reaction incorporated triazole in 20% of PVC, the optimal reaction conditions was evaluated. These conditions were used for the formation of new copolymers with different amounts of incorporated triazoles. The products obtained were used as a support for palladium, which is used as a catalyst in Suzuki-Miyaura reaction. All copolymers were characterized by infrared spectroscopy, Fourier transform spectroscopy (FTIR)
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Synthèse et évaluation angiogénique d'analogues du M6P / Synthesis and evaluation of angiogenesis analogues of the M6PMba Mintsa, Léa 17 December 2015 (has links)
L’angiogenèse, est le garant de l’intégrité vasculaire, grâce à la formation de nouveaux vaisseaux sanguins à partir des préexistants. Cette néovascularisation est régulée par des facteurs angiogéniques. Plusieurs stimuli participent au déséquilibre de la balance angiogénique, une vascularisation anormale en résulte. L’intérêt des thérapies actuelles est de restaurer une vascularisation normale, par ciblage des facteurs impliqués dans le processus angiogénique. Il fut démontré que le RM6P-CI est partie prenante dans ce mécanisme. Il a la particularité d’interagir avec plusieurs ligands, dont le M6P et ses dérivées.Il est question de savoir si le M6A, un dérivé isostère du M6P, se lie au RM6P-CI. Pour cela, le test CAM légèrement modifié, a été réapproprié pour confirmer premièrement l’activité pro-angiogénique du M6A. Deuxièmement la technique de cytométrie en flux est utilisée pour mettre en évidence l’interaction entre le M6A et le RM6P-CI. / Angiogenesis is the protector of vascular integrity, through the formation of new blood vessels from pre-existing vessels. The angiogenesis is regulated by the angiogenic factors. Several stimuli are involved in the angiogenic balance’s destabilization, which produces an unusual vascularization. The interest of conventional and targeted therapies is to restore a normal vascularization, by targeting all the factors which are involved in the angiogenic process. It has been demonstrated that the CI-M6PR is involved in this mechanism. This receptor has the distinction of having more binding sites, so a variety of ligands, including the M6P and its analogs. During this study we want to know if the M6P, isostere analog of M6P, interacts with the CI-M6PR. For this, we reappropriated the assay CAM, slightly modified, to confirm at first the pro-angiogenic activity of M6A. In a second step we will use the flow cytometry technique to highlight the interaction between the M6A and CI- M6PR.
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Polynuclear Coordination Assemblies : Synthesis, Crystal Structures And Magnetic BehaviorSengupta, Oindrila 11 1900 (has links) (PDF)
Construction of polynuclear metal assemblies from discrete 0D clusters to extend 3D networks, comprised of metal ions and bridging organic/inorganic ligands has attracted immense attention, owing to their intriguing network topologies and interesting properties. Proper ligand design and the appropriate choice of the metal center are of vital importance to the design of such polynuclear assemblies. One of the various attributes of polynuclear metal assemblies is magnetism. Magnetic materials can be constructed by incorporating magnetic moment carriers such as paramagnetic metals(V, Cr, Mn, Fe, Co, Ni, Cu) in presence of bridging ligands.
Though, one-atom oxo/hydroxo and two-atom cyanide bridges were of popular choices due to their short distance for transmitting strong magnetic coupling between the paramagnetic metal centers, it has been shown that, three-atom bridging ligands like carboxylate and azide (N3 ) are well-fitted moieties for this purpose since they offer a variety of magnetic interactions depending on their versatile bridging modes.
It has been well known that incorporation of anionic bridging ligand in presence of azide anion is a challenging task due to the competition between the 2nd anionic ligand with azide in self-assembly process. Incorporating both azide and carboxylate functionalities, a series of polymeric complexes has been synthesized and conversion of 0D discrete clusters to extended networks with the retention of basic core by fine tuning the ligands has been achieved.
Single-crystal to single-crystal transformation has received considerable attention in crystal engineering since it is difficult for crystals to retain single crystallinity after removal of the guest at high temperature. Interestingly single-crystal to single-crystal transformation was observed at high temperature for Co(II) formate-formamide complex and change in dimensionality from 3D to 0D was observed at high temperature for Cr(III) formate-formamide complex.
Multiferroic materials are those where both ferroelectricity and ferromagnetism coexist in the same phase. In general the transition metal d-electrons which are essential for magnetism reduce the tendency for off-center ferroelectric distortion. First tetrazole based miltiferroic coordination polymer of Co(II) metal ion in presence of azide has been successfully synthesized whereas its analogous Mn(II) complex showed different structural topology with interesting magnetic behavior. It has been also established in the present study, the important role played by hydrazine ligand to prevent oxidation of paramagnetic Co(II) to diamagnetic Co(III) system with the formation of a metal-inorganic assembly of Co(II) which exhibited spin-canted behavior.
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Vinylazide - Synthesen und ReaktionenMelzer, Antje 22 October 2001 (has links)
Die Möglichkeit der Synthese von Vinylaziden durch basenkatalysierte Umlagerungen von präparativ einfach zugänglichen Allylaziden wird an einer Reihe von akzeptor- und phenylsubstituierten Allylaziden sowie an substituierten 1-Azido-1H-indenen exemplarisch dokumentiert. Neben präparativen Gesichtspunkten werden auch mechanistische Details bezüglich der Isomerisierungsgeschwindigkeit und der Lage des Isomeriegleichgewichtes erörtert.
Ein weiterer Aspekt der Arbeit ist die mechanistische Untersuchung der nucleophilen Addition von Stickstoffwasserstoffsäure (HN3) an akzeptorsubstituierte Allene (Michael-Addition).
Durch die Übertragung dieser Synthesesequenz auf Hexa-1,2,4,5-tetraene (Diallene) lassen sich 1,4-Diazidobuta-1,3-diene erzeugen. Die thermische oder photochemische Anregung dieser Diazide führt im untersuchten Synthesebeispiel zur Bildung von zwei stabilen diastereomeren Bi-2H-azirin-2-ylen. Die Zuordnung der Konfiguration dieser Heterocyclen gelingt durch eine Einkristall-Röntgenstrukturanalyse. Thermisch oder photochemisch induzierte Valenzisomerisierungen zu Pyridazinen und Pyrimidinen, wie sie in Analogie für Bicycloprop-2-enyle als Valenzisomere des Benzols gefunden werden, spielen bei den untersuchten diastereomeren Bi-2H-azirin-2-ylen nur eine untergeordnete Rolle. Die favorisierten Reaktionen, insbesondere bei der Thermolyse, sind Epimerisierung und Fragmentierung, deren Verlauf durch kinetische Untersuchungen präzisiert wird.
Ferner wird gezeigt, daß auch einfache stereoisomere 2H-Azirine einer thermischen Äquilibrierung der Konfiguration unterliegen können.
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Synthesis and Reactions of α-Azido AlcoholsFirdous, Samia 27 January 2012 (has links)
Die vorliegende Arbeit beschäftigt sich mit der Untersuchung von a-Azidoalkoholen, welche über die Reaktion von aliphatischen sowie aromatischen Aldehyden mit HN3 leicht zugänglich sind und die im Gleichgewicht mit den jeweiligen Ausgangsstoffen vorliegen. Bei Raumtemperatur stellt sich dieses Gleichgewicht sehr schnell ein und man erhält spezifische Konzentrationen an Eduktaldehyd, Stickstoffwasserstoffsäure und a-Azidoalkohol. Die Reaktion von Aldehyden mit HN3 generiert dabei ein neues Chriralitätszentrum, wodurch die Umsetzung chiraler Aldehyde, wie z. B. von Zuckerderivaten, zwei anomere Produkte hervorbringt.
Die erstmalig erfolgreichen Synthesen zur Erzeugung von 4-Brom-4-methylpentanal sowie 4-Azido-4-methylpentanal werden ebenfalls beschrieben. Letztere Verbindung reagiert dabei ebenso wenig via einer intramolekularen 1,3-dipolaren Cycloaddition zum entsprechenden 4,5-Dihydro-1,2,3,4-oxatriazol-Derivat wie das analoge-Azidobutanal, was im Gegensatz zu Literaturangaben steht.
Des Weiteren werden einige interessante Reaktionen der a-Azidoalkohole untersucht. Die Oxidation mit Pyridiniumchlorochromat (PCC) bei –60°C führt zu Carbonylaziden. Die Photolyse bei –50°C generiert unter Stickstofffreisetzung Nitrene, welche mittels Wasserstoffwanderung und anschließender Tautomerisierung des resultierenden Intermediats zu Säureamiden umlagern. Die ebenfalls mögliche 1,2-Wanderung einer Gruppe R in a-Position führt dabei zu einem Intermediat, aus welchem sofort das entsprechende Formamid-Derivat entsteht. a-Azidoalkohole reagieren mit PBr3 in einer sauberen Reaktion durch die Substitution der Hydroxylfunktion unter Bildung der jeweiligen 1-Azido-1-brom-Verbindung. / In this work, α-azido alcohols which exist in equilibrium with the starting materials have been studied by the reactions of aliphatic and aromatic aldehydes with HN3. In some cases the title compounds can be isolated from the mixture at low temperature. At room temperature, however, the equilibrium is fast and there are again specific concentrations of the aldehyde, hydrazoic acid, and the α-azido alcohol. The reaction of aldehydes with HN3 creates a new chiral center and a chiral aldehyde, e.g. sugar derivatives, produces two anomeric products.
The first procedures to prepare 4-bromo-4-methylpentanal and 4-azido-4-methylpentanal are also reported. The latter compound and also the parent 4-azidobutanal do not lead to 4,5-dihydro-1,2,3,4-oxatriazoles by intramolecular 1,3-dipolar cycloaddition, although it was claimed in the literature.
Furthermore, some interesting reactions of the α-azido alcohols have been investigated. The oxidation of α-azido alcohols with pyridinium chlorochromate (PCC) at −60 °C leads to formation of carbonyl azides. The photolysis of α-azido alcohols at −50 °C generates nitrenes with liberation of dinitrogen, which lead to the formation of acid amides after the migration of hydrogen and subsequent tautomerism of the intermediate. 1,2-Migration of a group R in the α-position can produce an intermediate stage which is rapidly converted into formamide derivative. α-Azido alcohols react with PBr3 to give 1-azido-1-bromo derivatives in a clean reaction by substitution of hydroxyl group at the α-position.
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Functionalized Nanofiber Substrates for Nerve RegenerationSilantyeva, Elena A. 26 June 2019 (has links)
No description available.
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Neue binäre CN-Verbindungen sowie Vorläufersubstanzen von monomerem C3N4Richter, Sebastian 24 November 2014 (has links) (PDF)
Gegenstand dieser Arbeit sind Versuche zur Synthese neuer binärer Kohlenstoffnitride im Allgemeinen und von C3N4-Vorläuferverbindungen im Speziellen. Hierbei werden v. a. die Herstellung und die Eigenschaften organischer Polyazide beschrieben, die aufgrund ihrer Gefährlichkeit durch zahlreiche Folgereaktionen in weniger brisante Moleküle überführt werden mussten. Als Derivatisierungsreaktionen kamen hierbei beispielsweise die 1,3-dipolare Cycloaddition mit Norbornen und Cyclooctin, die STAUDINGER-Reaktion mit verschiedenen Phosphinen sowie die Aza-WITTIG-Reaktion zum Einsatz. Es konnten dabei u. a. zehn Röntgeneinkristallstrukturen erhalten und als Strukturbeweis aufgeführt werden. Zahlreiche hochaufgelöste Massenspektren sowie Elementaranalysen und NMR-Daten bestätigten außerdem alle neu erhaltenen Strukturen. Einen weiteren Schwerpunkt dieser Arbeit stellen Versuche zur Synthese von monomerem C3N4 dar, dessen Herstellung zwar nicht gelang, für dessen Bildung allerdings neue Möglichkeiten ausgehend von verschiedenen Edukten beschrieben werden. Darüber hinaus wurden bereits bekannte Moleküle auf ihre Eignung als C3N4-Vorläufer untersucht, wobei z. B. durch Azid-Addition an Nitrilgruppen unerwartete neue Produkte erhalten werden konnten.
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