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  • 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.
141

Syntéza a reaktivita hypervalentních fluoridů síry / Synthesis and reactivity of hypervalent sulfur fluorides

Ajenjo, Javier January 2019 (has links)
The pentafluorosulfanyl (SF5) group displays remarkable and unique properties, including large dipole moment, high electronegativity, high thermal and chemical stability, as well as high lipophilicity. However, only a few synthetic methods for the preparation of aromatic pentafluorosulfanyl building blocks have been developed to date. This work aims at improving availability and accessibility of aryl sulfurpentafluoride building blocks. In the first part of the work, the synthesis of aryl sulfurpentafluorides by the direct fluorination of diaryl disulfides with elemental fluorine is described. Nowadays, this synthetic strategy is used by industry on a multi-kilogram scale. However, the scope of the reaction is only limited to 3- and 4- nitro-1-(pentafluorosulfanyl)benzenes. In this work, the synthesis of various para-, meta- and ortho-substituted-(pentafluorosulfanyl)benzenes following the same approach was carried out. In the second part, the derivatization of aryl sulfurpentafluoride building blocks was investigated. Direct fluorination of 3-nitro-1-(pentafluorosulfanyl)benzene afforded 3-fluoro-5-nitro-1- (pentafluorosulfanyl)benzene. The titled compound was derivatized by two different processes: nucleophilic aromatic substitution (SNAr) of fluorine and vicarious nucleophilic substitution of...
142

Vers l'introduction douce de groupes fluorés émergents oxygénés et soufrés / New methodologies to introduce emerging fluorinated groups oxygenated and sulphurinated

Bouvet, Sébastien 18 November 2015 (has links)
Les travaux s’articulent autour du développement de nouveaux agents de fluoration et sur l’étude de leurs réactivités au cours de différentes réactions.Dans une première partie, nous décrivons la synthèse de nouvelles sources réactives de fluorure à partir de liquides ioniques de type imidazolium possédant un fluor en partie anionique. Les deux liquides ioniques [bmim][F] et [bdmim][F] obtenus ont ensuite été testés dans différents processus de monofluoration et de fluorodésulfuration oxydative.Une deuxième partie concerne le développement de réactifs de trifluorométhoxylation.Dans un premier temps, nous nous sommes attachés à synthétiser des nouveaux précurseurs de carbène possédant un groupement OCF3. Nous avons ensuite évalué leur réactivité au cours de différents processus. Dans un second temps, nous nous sommes axés sur la réactivité d’un composé FAR (Fluoroalkyl Amino Reagent) dans des réactions d’acylation aromatique.Enfin, le dernier chapitre rapporte l’étude du comportement électrochimique en réduction du gaz SF6, le but étant d’obtenir une nouvelle source radicalaire de SF5. Après une première partie analytique, l’hexafluorure de soufre a été engagé dans des processus d’électrosynthèse pour tenter de piéger les intermédiaires réactionnels issus de sa réduction. / The manuscript deals the development of new fluorinating reagents and their reactivity in various reactions.In the first part, we were interested in developing new fluoride sources from ionic liquids with imidazolium as the cationic part, and associated to the fluoride as anion. Two ionic liquids, [bmim][F] and [bdmim][F], were obtained. They were then tested in monofluoration and fluorodesulfurization reactions.The second chapter concerns the development of new trifluoromethoxylation reagents.We began by synthetizing new carbene precursors with an OCF3 group. We then evaluated their reactivities in different processes. A second part was centered on a FAR compound and its reactivity in aromatic acylation reactions.Finally, the last chapter describes the behavior of SF6 in electrochemistry reduction with different conditions, the aim being to have a new source of SF5 radical. After a first part concerning analytical studies of the sulfur hexafluoride, the aforementioned compound was engaged an electrosynthetic process to trap intermediate species coming from its reduction.
143

Nouvelle méthode d'activation du lien C-F promue par des donneurs de liaisons hydrogènes

Benhassine, Yasmine 13 June 2024 (has links)
La liaison C-F est la plus forte liaison simple que peut faire le carbone, elle est aussi particulièrement plus forte que toutes les autres liaisons carbone-halogène (enthalpie de dissociation à 298 K: CH3-F 480,7 kJ/mol; CH3-Cl 349,9 kJ/mol, etc.). Malgré la force de cette liaison, de nombreuses méthodes sont apparues dans les dernières années pour l’activer dans les composés aromatiques, vinyliques et aliphatiques. Typiquement, ces méthodes nécessitent des conditions fortement acides ou l'utilisation de métaux de transition. Nous avons développé une méthode d’activation de liaisons C-F par l’eau pour réaliser des réactions de substitution nucléophile de type SN2. La réactivité accrue du lien carbone-fluor est due aux liaisons hydrogène entre l'eau et l'atome de fluor, qui agit comme accepteur. Suite à ces travaux, nous avons étudié la réactivité des fluorures benzyliques en présence de donneurs de liaisons hydrogène plus forts que l’eau, tel que le 1,1,1,3,3,3-hexafluoropropan-2-ol (HFIP). Les résultats obtenus démontrent une réactivité inédite de type Friedel-Crafts (SN1). Une optimisation de la réaction a été effectuée. L'étendue de la transformation a été étudiée et les résultats obtenus nous ont permis de comprendre la réactivité du système en fonction des propriétés électroniques des fluorures de benzyle et des nucléophiles. Tous ces travaux ainsi que des études mécanistiques préliminaires seront présentés. / The carbon-fluorine bond is the strongest single bond that a carbon can have, it is also particularly stronger than any other carbon-halogen bonds (dissociation enthalpy at 298 K: CH3-F 480,7 kJ/mol; CH3-Cl 349,9 kJ/mol.). Despite the strength of this connection, numerous methods have emerged in recent years to turn it into aromatic and aliphatic vinyl compounds. Typically, these methods require strongly acidic conditions or the use of transition metals. We developed a C-F activation method with water to produce nucleophilic substitution reactions type SN2. The reactivity of carbon-fluorine bond is due to the hydrogen bonds between water and the fluorine atom, which acts as an acceptor. Following this work, we investigated the reactivity of benzyl fluoride in the presence of stronger hydrogen bond donor than water, such as 1,1,1,3,3,3- hexafluoro-2-propanol ( HFIP) The results show a Friedel-Crafts type unprecedented reactivity (SN1). An optimization of the reaction was carried out. The extent of the transformation has been studied and the results obtained have allowed us to understand the reactivity of the system based on electronic properties of benzyl fluorides and nucleophilic. All this work and preliminary mechanistic studies will be presented.
144

Odstraňování CO2 z bioplynu / CO2 removing from biogas

Kovář, Martin January 2012 (has links)
Research the Selexol, Rectisol, Fluor and Purisol technologies for the treatment of biogas to natural gas quality is the main job. The purified biogas must meet quality requirements, which sets out legislation Czech Republic. An important point is to build models of technology in the ChemCad software. Methods are analyzed with these models for the same output requirements. The result is to determine whether the technologies are suitable for biogas purification and implement, through research, simplified technical and economic evaluation.
145

Étude de la contribution catalytique à la stabilité des effluents en hydroconversion des résidus sous vide / Impact of catalyst on effluents stability during vacuum residues hydroconversion

Marchal, Charles 18 November 2010 (has links)
Ce travail porte sur la compréhension du phénomène d'instabilité qui se produit dans le procédé d'hydroconversion des résidus sous vide (RSV). Au delà de 60% de conversion du RSV, l'instabilité se manifeste par un dépôt solide d'hydrocarbures lourds dans les unités industrielles de conversion des résidus, ce qui empêche d'atteindre un niveau de conversion du RSV plus élevé. L'objectif de cette thèse consiste à mieux comprendre l'influence du catalyseur utilisé dans le procédé d'hydroconversion sur l'apparition du phénomène d'instabilité. Des catalyseurs dopés au fluor et sodium ont été préparés par ajout de dopants à la surface d'un catalyseur NiMo/Al2O3 de référence. Après leur caractérisation, les catalyseurs ont été testés sur charge réelle RSV en réacteur autoclave. Les tests catalytiques ont été réalisés à haute température dans les conditions industrielles (430°C) et à plus basse température (390°C), afin de favoriser les réactions catalytiques par rapport aux réactions thermiques. Les tests catalytiques réalisés à 390 et 430°C montrent une teneur en sédiments deux fois moins importante avec le catalyseur F-NiMo, ce qui est expliqué par une amélioration de la conversion des asphaltènes. Celle-ci est expliquée par l'amélioration des réactions d'hydrogénation et de l'acidité, et par une meilleure résistance au cokage à 390°C. L'effet de la température sur la stabilité a également été étudié. Les résultats démontrent que la teneur en sédiments des effluents est deux fois supérieure pour les tests réalisés à 430°C par rapport aux tests réalisés à 390°C. Cet accroissement de l'instabilité est attribué à un caractère plus aromatique et condensé des molécules qui précipitent (asphaltènes), qui ont en conséquence une tendance accrue à s'agréger, et par la désalkylation des molécules qui stabilisent (résines). / This work focuses on the instability phenomena occurring during vacuum residue hydroconversion. At high level of residue conversion, carbonaceous sediments (sediments) are formed and have detrimental effects on the industrial units during the hydroprocessing operations. The aim of this work is investigate the influence of the catalyst used inhydroconversion process on the sediments formation. Modified catalysts have been prepared by sodium and fluorine deposition on a NiMo/Al2O3 reference catalyst. After having been characterized, the catalysts have been tested in a perfectly stirred batch reactor. Catalytic tests have been performed at high temperature (430°C) in industrial conditions and at lower temperature (390°C) in order to favor catalytic reactions rather thermic reactions. The catalytic tests at the two temperatures show that the amount of sediments is two times lower with F-NiMo catalyst. This is explained by the improvement of asphaltenes conversion due to an increase of catalyst acidity and hydrogenation reactions. At 390°C, coking with F-NiMo catalyst is reduced so that porous volume is higher. The temperature effect on effluents stability has also been studied. Results show that the amount of sediments is twice lower at 390°C for a same catalyst. The increase of instability at 430°C is attributed to more condensed and aromatic asphaltenes and resins dealkylation which increase selfaggregation tendency of asphaltenes.
146

Nukleofilní zavedení fluorovaných funkčních skupin pomocí organofosforových sloučenin. / Nucleophilic introduction of fluorinated functional groups using organophosphorus compounds.

Opekar, Stanislav January 2014 (has links)
In the Introduction part of this thesis, the chemistry of organofluorine compounds is discussed, particularly the methods for the preparation of organofluorine compounds mainly by fluoroalkylation methods. Furthermore, the chemistry of fluorinated phosphonates, methods of their preparation, reactivity and biological activity is discussed. Additionally, the reactivity of fluoromethane derivatives is briefly mentioned and especially, the reactivity of diethyl fluoromalonate and fluorobisfenylsulfonylmethane is described. The Results and discussion part is devoted to the reactivity of three fluorinated phosphonates: tetraethyl fluoromethylenbisphosphonate, diethyl fluorophenylsulfonylphosphonate and previously not described diethyl fluoronitromethylphosphonate. These fluorinated phosphonates belong to the family of nucleophilic monofluoroalkylation reagents, meaning that these compounds are convenient starting materials for the synthesis of complex organic molecules containing the fluorine atom. The results deal with the reactivity of above mentioned fluorinated phosphonates, mainly with alkylation reactions, Horner-Wadsworth-Emmons reactions and conjugated additions. Also, other synthetic methods such as the Mitsunobu reaction or the palladium catalyzed allylation reaction were investigated; however,...
147

Synthèse des composés biologiquement actifs en utilisant des réactions photochimiques / Synthesis of biologically active compounds using photochemical reactions

Gomez fernandez, Mario Andres 09 January 2018 (has links)
En industrie chimique, on cherche continuellement des molécules biologiquement actives essentiellement pour les domaines pharmaceutique et agrochimique. De plus en plus les exigences à ces produits deviennent dures. Elles concernent, par exemple, les activités secondaires ou l'écotoxicité. En conséquence, un grand nombre de structures doit être testé pour trouver des composés actifs remplissant les propriétés imposées. En parallèle, les capacités dans l'industrie pour tester un grand nombre de composés différents en peu de temps ont considérablement augmentées. En conséquence, l'industrie cherche des nouvelles méthodes de synthèse pour accéder rapidement à une plus grande variété des structures moléculaires.Dans ce contexte, l'industrie chimique et pharmaceutique s'intéresse fortement aux réactions photochimiques appliquées en synthèse organique. Ces réactions permettent de synthétiser des composés en grande variété structurale inaccessibles par la synthèse organique conventionnelle. Les produits des réactions photochimiques sont une partie de l’espace chimique qui n’a pas encore été complètement exploré pour la recherche des structures avec de l’activité biologique.Dans les travaux de thèse presentés nous nous sommes interessés d’abord à la photocycloaddition [2+2] entre un groupement carbonyl et un alcène, la réaction de Paternò-Büchi. Nous avons utilisé cette reáction pour obtenir des oxétanes qui possèdent des groupements intéressants en agrochimie et au même temps des sites clés qui permettront d’autres transformations lors des étapes ultérieures. Par la suite nous avons exploré la réaction de Paternò-Büchi avec des alcènes fluorés. Les résultats ont été très encourageants. Nous avons découvert une nouvelle famille d’oxétanes fluorés très stables. Au vu de ses propriétés, ces produits peuvent être utilisés comme des <chassis moléculaires> pour l’obtention des composés biologiquement actifs. D’autre côté, une nouvelle reactivité photochimique a été découverte : il s’agit d’une réaction Photo-Wittig analogue. Cette reactivité chimique dépend des substituants sur le carbonyl. Nous pensons que cette réactivité chimique est directement liée à l’état excité du carbonyl. / In life sciences, there is a continuos research for new biological active molecules, this is true for both pharmaceultical industry and agrochemical industry. In the last years regulations have become more and more severe. In recent years, the technology for the test of new chemical compounds in industry has considerably evolved. Nowdays it is possible to test a vast number of compounds for the screening of biological activity in a short time. This means that industry is searching for new methodologies that allow the obtention of diverse chemical structures that can present biological activity.In this context, chemical industry, in particular, pharmaceutical and agrochemical industry are interested in the use of photochemical reactions in organic synthesis. Photochemical reactions allow the obtention of a variety of complex structures that are not easily obtained by classical methods. This chemical space has not been completly explored in the search of biological active compounds.In the works presented in this PhD research we first explored the [2+2] photocycloadtion of a carbonyl compound to an olefin, the called Paternò-Büchi reaction. We succesfully applied this reaction to obtain oxetanes wich posses agro-like substituents and key sites for further functionalization, a requirement demanded in industry. We also explored the use of fluorinated olefins in this photoreaction. The results are very promising: we discovered a new family of stable fluorinated oxetanes. These compounds can be used cas molecular scaffolds for the obtention of biological active compounds. At the same time, we discovered a new photochemical reactivity: a Photo-Wittig like reaction. This new reactivity depends on the substitution pattern of the carbonyl group. We hypothesize that the new reactivity depends on the excited state of the carbonyl compound.
148

Síntese, controle de qualidade e ensaios de eficácia e toxicidade in vitro do radiofármaco 18F Fluortimidina (18FLT)

Leonardo Tafas Constantino do Nascimento 22 August 2014 (has links)
Nenhuma / 3-Desoxi-3-[18F]Fluor-Timidina (18FLT) é um análogo radioativo do nucleosídeo timidina usado desde 1998 em exames de tomografia por emissão de pósitrons (PET) para diagnóstico de vários tipos de tumores, como de mama, pulmonar, colorretal, cerebral, entre outros. Seu uso amplia a cobertura dos exames PET em diagnóstico de câncer, já que existem limitações da [18F]Fludesoxiglicose (18FDG), o radiofármaco PET mais usado no mundo atualmente. Para implementação da produção de 18FLT, na Unidade de Pesquisa e Produção de Radiofármacos do Centro de Desenvolvimento da Tecnologia Nuclear (UPPR/CDTN), o módulo de síntese de 18FDG foi adaptado usando-se 3 protocolos nos quais se variou a concentração de etanol (0; 8 e 10% V/V). Também foram desenvolvidos testes de Controle de Qualidade, como pH, determinação de catalisador, determinação de etanol e acetonitrila, pureza química e radioquímica, entre outros. A formulação foi avaliada in vitro quanto a sua segurança, pelos ensaios de viabilidade metabólica (MTT) e toxicidade clonogênica, e quanto a sua eficácia para a detecção de tumores pelo ensaio de interação (Binding). Os rendimentos corrigidos obtidos da síntese de 18FLT foram 6,52%; 253% e 233% para o 1, o 2 e o 3 protocolo, respectivamente. O produto do protocolo 3 (Etanol 8%) apresentou menor citotoxicidade no teste in vitro MTT do que o do segundo (Etanol 10%). Além disso, a formulação de 18FLT e as impurezas químicas presentes na mesma não afetaram a clonogenicidade das células testadas. Com base nestes resultados o protocolo 3 foi escolhido como a síntese padrão de 18FLT. A interação da 18FLT com as linhagens celulares foi saturável, com ligação específica maior que 90%, atestando a eficácia do radiofármaco na detecção de tumores. A afinidade do radiofármaco 18FLT por células de glioblastoma humano (U87MG) foi da ordem de 0,24 &#956;mol/L (Kd). Por fim, constatou-se que quantidades adicionais de timidina e clorotimidina, duas impurezas presentes na formulação, reduziram significativamente a interação de 18FLT (IC50 ~ 1 - 34 &#956;mol/L) com as células tumorais, o que pode reduzir sua eficácia para o diagnóstico. Assim, sugere-se que um valor máximo seja estabelecido para a concentração destas impurezas como um dos critérios de Pureza Química de 18FLT, baseando-se no ensaio de eficácia de interação. Portanto, a UPPR/CDTN está apta a fornecer rotineiramente o radiofármaco 18FLT para estudos não clínicos e clínicos, de acordo com os requisitos de Boas Práticas de Fabricação de Medicamentos exigidos pela ANVISA. / 3-Deoxy-3-[18F]Fluorothymidine (18FLT) is a Thymidine radioactive analog that is being used since 1998 for cancer diagnostics by Positron Emission Tomography (PET) for several types of cancer, as breast, lung, colorectal, brain, among others. Its use extends coverage of PET scans in diagnosis of cancers in certain organs and tissues, since there are limitations of [18F] Fludeoxyglucose (18FDG), which is the most used PET radiopharmaceutical in the world today. An 18FDG synthesis module was adapted to implement 18FLT production in Research and Production Unit of Radiopharmaceuticals from Center of Nuclear Technology Development (UPPR/CDTN). Three protocols were used varying the concentration of ethanol (0%, 8% and 10%). Quality control tests were also developed, as pH, catalyst determination, ethanol and acetonitrile determination, chemical and radiochemical purity, amongst others. The formulation was evaluated in vitro for its safety, using the metabolic viability (MTTs assay) and clonogenic toxicity assays, and for its effectiveness in tumors, using the binding test. The corrected yields were 6.52%; 253%; and 233% for the first, second and third synthesis protocols, respectively. The third protocol (Ethanol 8%) was found to be less cytotoxicity comparing to the second one (Ethanol 10%). Furthermore, 18FLT chemical impurities and the entire formulation did not affect the clonogenicity of the cells in Clonogenic Assay. Based on these results the protocol 3 was chosen as the standard 18FLT synthesis. The interaction of 18FLT with the cell lines was saturable, with specific binding higher than 81%, confirming the effectiveness of the radiopharmaceutical in tumor detection. The affinity between 18FLT and human glioblastoma cells (U87MG) was found to be 0.24 &#956;mol/L (Kd). Finally, it was found that additional quantities of thymidine and chlorothymidine reduced significantly 18FLT interaction (IC50 ~ 1 - 34 &#956;mol/L) with tumor cells, which can reduce its effectiveness in PET diagnosis. For this reason it is suggested that a maximum value must be set for the concentration of these impurities in the 18FLT Chemical Purity quality control test based in efficacy binding assays. Therefore, CDTN is able to routinely provide 18FLT radiopharmaceutical for clinical and non clinical studies, according to the Brazilian Good Manufacturing Practices for Radiopharmaceuticals required by ANVISA.
149

Desfluoretação de meios aquosos via adsorção de flúor em esferas hidrogel de Fe-PVA

Felipe Wallysson Ferreira de Oliveira 09 February 2015 (has links)
Nenhuma / O processo sol-gel foi usado para nanoestruturar partículas de oxihidróxido de ferro e aprisiona-las na estrutura de micro-, meso- e macroporos + macroburacos (poros de dimensões micrométricas) da rede polimérica do PVA (álcool polivinílico). Esferas hidrogel de oxihidróxido de Fe-PVA com (3433 63 &#956;m) e sem (2833 69 &#956;m) macroburacos foram obtidas. Espectroscopia Mössbauer mostra que as esferas obtidas têm nanopartículas (majoritariamente &#8804;20 nm) de &#945;-Fe2O3, &#61543;-Fe2O3, &#945;-FeOOH e fases ainda superparamagnéticas a 20 K. As esferas hidrogel obtidas possuem elevada estabilidade química e boa rigidez mecânica. Capacidade adsortiva: 77,9 e 204,9 mgF/g, respectivamente para as esferas hidrogel sem (bom ajuste aos modelos de Langmuir e Freundlich) e com (bom ajuste ao modelo de Freundlich) macroburacos. Nos dois tipos de esferas, o mecanismo de quimissorção é predominante, mas o modelo de difusão intrapartícula sugere que o mecanismo de adsorção é mais complexo. Quatro ciclos de adsorção no modo coluna mostram uma pequena queda da eficiência de captura do F de 61,8 para 56,2%; neles, dessorção com solução NH3 min. 25% em peso mostra uma eficiência variando entre 95,8 e 98,8%. A estratégia de nanoestruturar as partículas de oxihidróxido de ferro e introduzir macroburacos na rede polimérica do PVA foi eficaz e realmente reforçou a captura do F. / The sol-gel process was used to nanostructure iron oxyhydroxide particles and to trap them into the structure of micro-, meso-, and macropores + macroholes (micrometer size pore) of the PVA (polyvinyl alcohol) polymeric network. Iron oxyhydroxide-PVA hydrogel spheres with (3433 63 microns) and without (2833 69 microns) macroholes were obtained. Mössbauer spectroscopy shows that the obtained spheres have nanoparticles (mainly &#8804;20 nm) of &#945;-Fe2O3, &#61543;-Fe2O3, &#945;-FeOOH, and phases still superparamagnetic at 20 K. The obtained hydrogel spheres have high chemical stability and good mechanical rigidity. Adsorptive capacity: 77.9 and 204.9 mgF/g, respectively for the hydrogel spheres without (fit well by the Langmuir and Freundlich models) and with (fit well by the Freundlich model) macroholes. In both types of spheres, the chemisorption mechanism is predominant, but the intraparticle diffusion model suggests that the adsorption mechanism is more complex. Four cycles of adsorption in the column mode show a small decrease of F capture efficiency from 61.8 to 56.2%; therein, desorption with NH3 solution min. 25 wt% shows an efficiency ranging between 95.8 and 98.8%. The strategy to nanostructure particles of iron oxyhydroxide and to introduce macroholes into the PVA polymer network was effective and really reinforced the F capture. Keywords: fluorine;
150

Nouvelles voies de synthèse énantiosélective pour l'accès à des composés difluorométhylés / Development of new strategies to access enantiopure difluoromethylated compounds

Batisse, Chloé 07 December 2018 (has links)
En dépit de sa rareté au sein des produits naturels et des processus biologiques, le fluor joue un rôle de plus en plus important dans nos vies quotidiennes. Un atome de fluor ou un groupement fluoré, lorsqu’il fait partie d’une molécule biologiquement active, permet d’améliorer drastiquement ses propriétés physiques, chimiques et biologiques. Le groupement -CHF2, en plus de posséder les propriétés remarquables communes à de nombreuses espèces émergentes fluorées, est considéré comme un bioisostère des groupements hydroxyle, thiol et amino. Il peut également être engagé dans des liaisons de type hydrogène grâce à son proton acide. Cependant, les voies de synthèse permettant d’introduire stéréosélectivement le groupe -CHF2 sont encore peu nombreuses. Par exemple, seuls peu de groupes ont concentré leurs efforts sur la synthèse d’alcools α,α-difluorométhylés. Afin de remédier à ce manque de méthodologies, deux stratégies ont été imaginées au sein de notre équipe. La première consiste à utiliser un sulfoxyde α,α-difluorométhylé énantiopur en tant qu’inducteur de chiralité. La seconde méthode repose sur l’utilisation de cyclopeptoïdes chiraux lors de la difluorométhylation énantiosélective de dérivés carbonylés dans des conditions de catalyse à transfert de phase. Ces deux stratégies ainsi que les résultats qui ont été obtenus au cours de ce projet de thèse sont exposés dans le présent manuscrit. / Despite being largely absent from natural products and biological processes, fluorine plays an increasingly important role in numerous areas of our daily life. The presence of fluorine atoms or fluoroalkyl groups in bioactive molecules can indeed deeply modify their physical, chemical and biological properties. In addition to these outstanding properties common to many emerging fluorinated groups, the -CHF2 group has been shown to be an interesting bioisostere of hydroxyl, thiol and amine groups and a strong hydrogen bond donor. However, in contrast to enantioselective trifluoromethylation, the enantioselective introduction of a difluoromethyl group is still in its infancy. For instance only few examples in the literature describe the synthesis of enantioenriched α,α-difluoromethyl alcohols. As part of our study to overcome this scarcity, we envisaged two different strategies to synthesise these compounds. The first method aimed to access highly enantioenriched α,α-difluoromethyl alcohols by using an enantiopure aryl α,α-difluoromethyl sulfoxide as chiral and traceless auxiliary. Phase transfer catalysis was chosen as a second strategy for the enantioselective difluoromethylation of carbonyl derivatives in presence of chiral cyclopeptoïds. Those two methods and the results obtained are discussed in this manuscript.

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