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Ryzhakov, Dmytro. "Désaromatisation radicalaire d'indoles pour la synthèse de spiroindolines trifluorométhylées ou phosphorées." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS366.
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Les spirooxindoles se retrouvent fréquemment dans les produits naturels et les composés biologiquement actifs. Certains principes actifs pharmaceutiques contenant un motif spirooxindole ont également été décrits, stimulant un grand intérêt pour la construction et la modification de ce squelette. Cependant, peu de travaux ont été réalisés pour remplacer le carbonyle en position 2 par un autre groupe fonctionnel d’intérêt. Basées sur l’expertise reconnue de notre équipe en désaromatisation d’indoles par umpolung et l’importance des fonctions CF₃ et PO(OR)₂ nous avons entrepris la synthèse de 3,3-spiroindolines substitueés en position 2 par un trifluoromethyl ou un phosphonate. Nous avons ainsi généré des radicaux trifluoromethyl ou phosphonyl par oxydation respective de trifluoromethyl sulfinate de sodium et de phosphites. Les espèces radicalaires obtenues peuvent ensuite s’additionner sur la position 2 des indoles et effectuer la désaromatisation d’indolesSpirooxindoles are frequently found in natural products and biologically active compounds. Certain pharmaceutical active ingredients containing a spirooxindole motif have also been described, stimulating great interest in the construction and modification of this structures. However, not a lot of work has been done to replace the carbonyl in position 2 with another functional group of interest. Based on the recognized expertise of our team in deflation of indoles by umpolung and the importance of CF₃ and PO(OR)₂ functions, we have undertaken the synthesis of 3,3-spiroindolines substituted in position 2 by a trifluoromethyl or a phosphonate . We have thus generated trifluoromethyl or phosphonyl radicals by respective oxidation of sodium trifluoromethyl sulfinate and phosphites. The radical species obtained can then be added to the position 2 of the indoles and perform the dearomatization of indoles
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Knappke, Christiane [Verfasser]. "Untersuchungen zur Umpolung von Alkylhalogeniden durch N-heterocyclische Carbene / Christiane Knappke." München : Verlag Dr. Hut, 2011. http://d-nb.info/1011441578/34.
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Patra, A. "N-heterocyclic carbene-organocatalyzed umpolung of aldehydes and imines for new synthetic transformations." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2017. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/4272.
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Esgulian, Mathieu. "Oxyhomologation diastéréosélective de la sérine : développement de la méthodologie MAC." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS392/document.
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La méthodologie MAC consiste à employer des réactifs umpolung pour permettre l’insertion formelle d’une fonction carbonyle entre un électrophile et un nucléophile. Cette thèse est consacrée à l’oxyhomologation diastéréosélective de la L-sérine grâce à un développement significatif de la méthodologie MAC à trois composants en one-pot, conduisant à l’obtention de dérivés orthogonalement protégés de l’acide α, γ-dihydroxy-β-aminobutyrique. Ce dernier est une brique moléculaire acyclique à 4 atomes de carbone hautement fonctionnalisée qui est souvent intégrée dans les squelettes de molécules biologiquement actives.Nous avons tout d’abord étudié la synthèse de réactifs MAC silylés à partir du malononitrile. La synthèse du H-MAC-TBS a été optimisée et deux nouveaux réactifs MAC silylés, le H-MAC-TES et le H-MAC-TBDPS, ont été préparés.Dans un premier temps, nous avons étudié l’oxyhomologation du N-Boc-O-Bn-L-sérinal avec le H-MAC-TBS en présence de différents alcools dans des conditions réactionnelles douces. En présence de méthanol, des α, γ-dihydroxy-β-aminobutanoates de méthyle orthogonalement protégés ont été préparés avec des bons rendements et avec un ratio diastéréoisomérique syn/anti = 80/20.L’utilisation du H-MAC-TBDPS a permis d’améliorer la diastéréosélectivité de la réaction MAC (syn/anti = 90/10). L’étude des différents modes de cyclisation des α, γ-dihydroxy-β-aminobutanoates de méthyle a été réalisée par la suite. Des hétérocycles fonctionnalisés à 3, 5 et 6 chaînons ont été ainsi sélectivement synthétisés.De nouvelles oxazolidinones et oxazolines hautement fonctionnalisées ont été préparées de cette façon. En revanche, malgré nos efforts approfondis, une cyclisation pour donner un hétérocycle à 4 chaînons n’a pas été réalisée.L’absence de réactivité de la fonction alcool libre en α de ces esters N-protégés et γ activés a été inattendue.Dans un deuxième temps, nous avons étudié l’oxyhomologation de l’aldéhyde de Garner, un dérivé cyclique N,O-protégé du L-sérinal, par des réactions MAC. En présence de divers nucléophiles, cette réaction a conduit diastéréosélectivement à des esters et des amides protégés de l’acide α, γ-dihydroxy-β-aminobutyrique avec des bons rendements et avec une diastéréoselectivité anti, allant jusqu’à un ratio diastéréoisomérique syn/anti = 10/90 en utilisant le H-MAC-TBDPS. Il s’agit des premiers exemples de diastéréosélectivité antiobservée pour une réaction MAC. Des hétérocycles fonctionnalisés à 3 et 5 chaînons ont été sélectivement synthétisés et, grâce à une oxydation sélective en position γ, des dérivés de l’acide érythro-β-hydroxyaspartique et de l’érythro-β-hydroxyasparagine orthogonalement protégés ont été préparésMAC methodology is a synthetic technique which employs an umpolung reagent to formally insert a carbonyl function between an electrophile and a nucleophile. This thesis is devoted to the diastereoselective oxyhomologation of L-serine thanks to a significant development of 3-component one pot MAC methodology, providing a synthesis of orthogonally-protected derivatives of α, γ-dihydroxy-β-aminobutyric acid. This latter is a highly functionalized, acyclic, 4-carbon molecular building block which is a constituent part of various biologically active molecules.The synthesis of silylated MAC reagents from malononitrile was first studied. H-MAC-TBS’s synthesis was optimized and two new silylated MAC reagents, H-MAC-TES and H-MACTBDPS,were prepared.In a first study, the oxyhomologation of N-Boc-O-Bn-L-serinal was examined using H-MACTBS and a panel of alcohols in mild conditions.Methyl esters of orthogonally-protected α, γ-dihydroxy-β-aminobutanoic acid were prepared in good yields and with a diastereoisomeric ratio syn/anti = 80/20. The use of H-MAC-TBDPS improved the diastereoselectivity of the MAC reaction to syn/anti = 90/10.Subsequently, different cyclization modes of methyl α, γ-dihydroxy-β-aminobutanoate were investigated, leading to the selective synthesis of functionalized 3-, 5- and 6-membered ring heterocycles, including new highly functionalized oxazolidinones et oxazolines. In contrast, despite considerable efforts, we were unable to induce cyclisation to forma a 4-membered ring heterocycle, due to the surprising lack of nucleophilicity of the free alcohol function in the acyclic precursors.In a second study, we examined the oxyhomologation of Garners aldehyde, a cyclicN,O-protected derivative of L-serinal, using a selection of nucleophiles via one-pot MAC methodology. These reactions furnished protected ester and amide derivatives of α, γ-dihydroxy-β-aminobutyric acid in good yields with an anti diastereoselectivity with a ratio as high as syn/anti = 10/90 when H-MAC-TBDPS was used as the MAC reagent. These are the first known examples of MAC reactions which proceed with anti diastereoselectivity.Functionalized 3- and 5-membered ring heterocycles were prepared from these adducts,and via selective oxidation at the γ-position,orthogonally-protected derivatives of erythro-β-hydroxyaspartic acid and erythro-β-hydroxyasparagine were prepared
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RAGNO, Daniele. "Reactivity of Alpha-Diketones in Umpolung Catalysis and Enantioselective Sulfoxidation by Novel Titanium Complexes." Doctoral thesis, Università degli studi di Ferrara, 2016. http://hdl.handle.net/11392/2403389.
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Nella continua ricerca di metodologie atte alla formazione di nuovi legami carbonio-carbonio, l’organocatalisi svolge un ruolo sempre più fondamentale; in questo contesto, la catalisi di Umpolung, che prevede l’inversione di reattività di un dato substrato, rappresenta un’importante via per accedere a nuove strategie sintetiche. All’interno di quel gruppo di molecole in grado di fornire reattività di umpolung, gli α-dichetoni rappresentano senza dubbio substrati molto interessati ed innovativi.
Alla luce di queste premesse, la reattività di α-dichetoni di-arilici è stata oggetto dei nostri studi. Inizialmente è stata valutata la reattività in reazioni di tipo cross-benzoinico con aldeidi, introducendo un nuovo catalizzatore di umpolung, il metil solfonil (dimsile) carbanione, con ottimi risultati in termini di efficienza di reazione e di chemoselettività.
La messa a punto di questa metodologia ha inspirato lo sviluppo di un nuova strategia sintetica per l’accesso a 1,2-dichetoni asimmetrici, che ha previsto una prima reazione cross-benzoinica catalizzata dall’anione dimsile , seguita da un’ossidazione in situ con riscaldamento a microonde.
Successivamente, si è passati all’impiego di α-dichetoni di-arilici in reazioni di addizione nucleofila con accettori di Michael; in questo caso è stata sviluppata una nuova reazione di doppia aroilazione catalizzata dal metil solfonil anione. E’ stato infine conferito un ulteriore valore aggiunto ai prodotti di reazione grazie ad un successivo stadio ossidativo, che ha consentito l’accesso ai corrispettivi alcheni tetrasostituiti.
Inoltre, uno degli aspetti più rilevanti della nostra attività di ricerca è consistito nell’indagine meccanicistica supportata da misure di tipo NMR ed ESI-MS. In questo contesto, è stato recentemente condotto lo studio ESI-MS della reazione di ossidazione aerobica di aldeidi catalizzata, da N-eterociclo carbeni (NHC). Mediante l’utilizzo di un NHC opportunamente funzionalizzato è stato possibile individuare le diverse specie e gli equilibri coinvolti nel processo catalitico.
Alla luce dell’esperienza pregressa del mio gruppo di ricerca nel campo della chimica in flusso, diversi processi di umpolung, quali reazioni di tipo benzoinico, aciloinico e di Stetter, sono stati studiati utilizzando microreattori monolitici tiazolio-funzionalizzati in regime di flusso.
Infine, durante il periodo svolto presso il gruppo del Prof. Berkessel, l’attività di ricerca si è incentrata sulla sintesi e l’impiego di ligandi cis-DACH-salalen in reazioni di solfossidazione stereoselettiva catalizzate da complessi di Titanio, utilizzando H2O2 come ossidante; durante questo lavoro è stato
messo a punto un solido protocollo per lo step di solfossidazione enantioselettiva della sintesi dell’esomeprazolo.In the investigation of effective chemical transformations, organocatalyzed carbon-carbon bond forming reactions play an outstanding role. Particularly, the inversion of the typical reactivity of a given substrate (umpolung) opens up new and unconventional synthetic pathways. In the continuous research of new acyl anion precursors, α-diketones actually represent innovative and efficient substrates. In this regard, the it was studied the umpolung reactivity of α-diketones confirming their crucial role as acyl anion precursors; after previous investigations by our group on dialkyl diketones, we focused our research on diaryl diketones. First, their reactivity in the cross-benzoin reaction with aldehydes was evaluated, introducing a new umpolung catalyst, the methyl sulfinyl (dimsyl) anion, with great results in terms of yields and chemoselectivity. This new optimized procedure opened a new synthetic route towards the synthesis of unsymmetrical αdiketones, thanks to a one-pot two-step process that involved a first cross-benzoin reaction catalyzed by the dimsyl anion, followed by in situ oxidation performed under microwave conditions. As a logical development of our research, the reactivity of diaryl 1,2-diketones with Michael acceptors in “Stetter-like” reactions was investigated; a new double aroylation reaction catalyzed by the methyl sulfinyl carbanion was discovered. The utility of the resulting 2-benzoyl-1,4-diones was also demonstrated by their facile conversion into the corresponding tetrasubstituted olefins. Investigation of reaction mechanisms by NMR and ESI-MS analysis represented an important part of our work. In this regard, a charge-tagged N-heterocyclic carbene (NHC) was employed as mass spectrometric probe to identify the species involved in the different oxidation steps of the aerobic NHC-catalyzed oxidation of aldehydes. Moreover, in continuation of the reserach of our group in the flow chemistry field, we prepared thiazolium-functionalized monolithic microreactors and demonstrated their synthetic potential in continuous-flow umpolung transformations such as benzoin, acyloin-type, and Stetter reactions. Finally, during my period in Prof. Berkessel group, a series of cis-DACH-derived salalen ligands were synthetized and their activity evaluated in the titanium-catalyzed asymmetric sulfoxidation of thioethers with aqueous hydrogen peroxide; a solid methodology for the last enantioselective sulfoxidation step of Esomeprazole synthesis was developed.
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Le, Xuan-Tien. "Nouvelles réactions d’allylations induites par le samarium divalent. Application à la modification contrôlée de dérivés de l’acide sialique." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112073.
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Le couplage croisé entre les esters allyliques et les composés carbonylés promu par le diiodure de samarium est une méthode efficace pour la formation de liaisons carbone-carbone. Une approche « umpolung » de réaction entre un composé carbonylé électrophile et un allylsamarien nucléophile, obtenu sans la réduction préalable d’espèces de type π-allylmétal de transition intermédiaires, fournirait une nouvelle voie plus simple pour la construction de cette liaison dans des conditions douces.Les esters allyliques de type dihydropyranyle se sont montrés d’excellents substrats dans les réactions d'allylation, d’aldéhydes ou de cétones, induites par le diiodure de samarium évitant ainsi l'utilisation de catalyseurs au palladium ou d’un autre additif. En série glycal, la nature et la configuration du substituant en position C-4 jouent un rôle très important à la fois sur le rendement et sur la structure des produits modifiés. Les couplages réducteurs directs ont lieu régiosélectivement en C-3 avec une stéréochimie relative 3,4-trans. La même stratégie appliquée aux dérivés Neu5Ac2en de l’acide sialique a permis d’obtenir par réactions à basse température, les produits de couplage en C-2 avec des rendements quantitatifs et une parfaite régio- et stéréosélectivité. Cette transformation donne un nouvel accès facile, rapide et très efficace aux α-C-sialosidesThe cross-coupling of allylic esters and carbonyl compounds promoted by samarium diiodide is an efficient method for the formation of carbon-carbon bonds. An umpolung approach, reaction between a carbonyl electrophile and an allyl samarium nucleophile, without the prior reduction of the intermediate π-allyl transition metal complexes, would provide a simple route for this bond construction under mild conditions.Dihydropyranyl allylic esters have been found to be excellent substrates for carbonyl allylation reactions mediated by samarium diiodide – without the use of palladium catalysts or any other additive. In glycal series, the nature and the configuration of the substituent at the C-4 position play crucial roles both on yields and structures of the modified products. The direct reductive couplings take place regioselectively at C-3 with a 3,4-trans relationship. Applied to Neu5Ac2en derivatives of sialic acid, the same strategy furnished the coupling products at the anomeric position in quantitative yields and with a perfect regio- and stereoselectivity. This transformation provides an easy, rapid and efficent access to α-C-sialosides
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Vogt, Monika [Verfasser]. "Umpolung von Allyl-Palladium-Komplexen und Anwendung in der Synthese von Naturstoff-Fragmenten / Monika Vogt." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover, 2010. http://d-nb.info/1008410608/34.
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Kipke, Andreas [Verfasser]. "Kupfer-katalysierte oxidative Decarbonylierung chiraler Aldehyde und Untersuchungen zur Umpolung von Allyl-Palladium-Komplexen / Andreas Kipke." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2012. http://d-nb.info/1029588872/34.
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DI, CARMINE Graziano. "Organo- and bio-catalytic approaches to the synthesis of biologically relevant compounds by the Umpolung strategy." Doctoral thesis, Università degli studi di Ferrara, 2019. http://hdl.handle.net/11392/2488244.
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The design of new reactions for carbon-carbon bond formation is certainly the main field in which the efforts of organic chemists have been focused in the last forty years. In addition, the undoubted benefit brought by catalysis has made possible the exploration of new and previously unknown reactivities, which have paved the way for the synthesis of complex molecules in a more efficient manner.
In this regard, our group has been involved for years in the investigation of the reversal reactivity of substrate molecules (umpolung), and during my period as Ph.D. student the activity has been mostly devoted to the exploration of this type of reactivity through two main catalytic approaches, namely organocatalysis and biocatalysis. The organocatalytic strategy was successfully employed in the synthesis of imidazoline-2-thiones via a domino process, which was characterized by the formation of a new carbon-carbon bond through an aza-benzoin reaction promoted by a N-Heterocyclic Carbene (NHC) catalyst. Afterwards, a new protocol was developed for the chemo- and enantioselective dearomatization of activated pyridinium salts through the NHC-catalyzed nucleophilic addition of umpoled aldehydes. Finally, the last work based on an organocatalytic approach dealt with the desymmetrization of 1,4-dihydropyridines by chiral NHC-oxidative catalysis.
In the context of biocatalysis, the synthetic potential of the enzyme/substrate pair Acetoin: Dichlorophenolindophenol Oxidoreductase from Bacillus licheniformis / methyl acetoin was efficiently exploited for the preparation of optically active phenyl acetyl carbinols ((S) -PACs). In addition, the same enzyme / substrate pair was demonstrated to be extremely effective in the synthesis of dissymmetric acyloins.
At the end of my doctoral course, during my period abroad in the group of Prof. Darren J. Dixon at the University of Oxford, I was involved in a research program dealing with the activation of amides promoted by Iridium complexes. In this regard, a new methodology was developed for the synthesis of substituted pyrrolidines, which were obtained through 1,3-dipolar cyclization reactions between acrylates and azomethine ylides generated in situ by catalysis with the Vaska complex in a reductive environment.La progettazione di nuove reazioni che permettono la formazione di legami carbonio-carbonio è sicuramente il campo principale in cui si sono focalizzati gli sforzi dei chimici organici negli ultimi quarant’anni. In aggiunta, l’indubbio beneficio portato dalla catalisi in tale ambito ha reso possibile l’esplorazione di nuove reattività prima sconosciute, che hanno spianato la strada alla sintesi di molecole complesse, in maniera sempre più efficiente. Su questa linea, il nostro gruppo si è inserito da anni con la premessa di esplorare in maniera critica la reattività che porta all’inversione della naturale polarità nei substrati, e durante il mio periodo di dottorato l’attività svolta ha previsto l’indagine di tale reattività attraverso i suoi due approcci più importanti (organocatalisi e biocatalisi). La via organocatalitica è stata impiegata con successo nella sintesi di imidazoline-2-tioni mediante un processo domino che ha coinvolto la formazione di un nuovo legame carbonio-carbonio, tramite una reazione aza-benzoinica promossa da un carbene N-eterociclico (NHC acronimo del termine inglese N-Heterocyclic Carbene). A seguire è stato messo a punto un protocollo per la dearomatizzazione di sali di piridinio, attivati da un gruppo elettron-attrattore in posizione 3 dell’anello. Questi ultimi hanno ricoperto il ruolo di elettrofili nell’addizione di aldeidi attivate da NHC chirali. Ed infine, l’ultimo lavoro inerente l’organocatalisi, ha riguardato la desimmetrizzazione di 1,4-diidropiridine tramite catalisi da NHC chirali in ambiente ossidativo. Nell’ambito della biocatalisi la coppia enzima/substrato, Acetoin:Dichlorophenolindophenol Oxidoreductase from Bacillus licheniformis / metil acetoino, è stata impiegata efficacemente nella preparazione di fenil acetil carbinoli otticamente attivi ((S)-PAC). In aggiunta, la medesima coppia enzima/substrato si è rivelata essere estremamente efficiente per sintesi enantioselettiva di aciloini dissimmetrici. Al termine del mio percorso dottorale, durante il mio periodo svolto all’estero presso il gruppo del Prof. Darren J. Dixon (Università di Oxford), mi sono occupato dell’attivazione di ammidi mediante complessi di Iridio. Nella fattispecie è stata sviluppata una metodologia che porta alla sintesi di pirrolidine sostituite, attraverso una reazione di ciclizzazione 1,3-dipolare, resa possibile dalla formazione in situ di azometinilidi grazie alla reattività del complesso di Vaska in ambiente riduttivo.
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Marquet, Bernard. "Electrofluoration en position benzylique." Lyon 1, 1990. http://www.theses.fr/1990LYO10196.
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L'oxydation anodique de derives benzyliques fonctionnalises dans cette position par un groupement electro-attracteur (carbonyle, nitrile, sulfonate) dans l'acetonitrile en presence de trihydrofluorure de triethylamine permet d'introduire un atome de fluor sur le chainon benzylique, via un mecanisme transitant par un carbocation destabilise. En serie paramethoxylee, les mono et les difluorures benzyliques sont obtenus avec de bons rendements quel que soit le groupement electro-attracteur. Pour les autres structures, la formation concurrentielle d'acetamide, ainsi qu'une fluoration du noyau aromatique sont observees. L'utilisation du sulfolane comme solvant en remplacement de l'acetonitrile permet d'eviter l'acetamidation. La fluoration de derives paramethyles a ete egalement etudiee. Elle conduit a une fonctionnalisation regioselective de ces composes. Les principaux facteurs responsables de cette regioselectivite ont ete examines
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PACIFICO, Salvatore. "Sintesi di glicopeptidi mediante le reazioni tiol-ene/ino e studio della reattività di Umpolung di α-dichetoni." Doctoral thesis, Università degli studi di Ferrara, 2013. http://hdl.handle.net/11392/2388912.
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It is well established that protein glycosylation, a bioorthogonal process, is a posttranslational modification that profoundly affects protein folding, stability, immunogenicity, and biological properties and activities. In this regard, while native O- and N-glycosidic bonds of glycopeptides are prone to hydrolytic cleavage by O- and N-glycosidases, synthetic C- and S-analogs are expected to be stable toward such enzymatic degradation. Therefore, much effort has been devoted in the last decades to synthesizing C- and S-glycosyl amino acids and their assembly in glycopeptides. They with these non-native linkages can be used as probes for biochemical studies and leads in drug discovery, such as, for example, vaccines. In the first part of this thesis project we developed two routes to synthesis of S-glycopeptides. One route consists of S-glycosyl amino acid synthesis from photoinduced addition of sugar thiols to alkenyl glycine (TEC) followed by incorporation of this amino acid into a peptide. The second route, that is, specific for a cysteine containing peptide such as glutathione, involves peptide S-homoallylation followed by TEC with sugar thiol. We also demonstrated the selective propargylation of cysteine-containing peptides followed by photoinduced thiol-yne coupling with glycosyl thiols as an effective one-pot two-step platform for the dual glycosylation of peptides. By this strategy, we also performed the sequential glycosylation and biotinylation of peptides.
In recent years, N-heterocyclic carbenes (NHCs) have attracted considerable interest due to their unique features, which allow them to be used as ligands for organometallic catalysis, reagents in the synthesis of heterocycles, and efficient organocatalysts in umpolung transformations. In the latter sub-area of research many efforts have been devoted to the realization of highly stereoselective versions of the classical benzoin and Stetter reactions through optimal pre-catalyst design, to the discovery of new transformations, and to the umpolung of electrophiles alternative to aldehydes and pyruvates, mainly acylsilanes and Michael acceptors. In this thesis, our group has recently demonstrated the capability of linear and cyclic dialkyl α-diketones to undergo polarity reversal under thiazolium carbene catalysis in benzoin-type and Stetter reactions, and thus act as a novel class of acyl anion precursors. Contrarily, it has been observed that diaryl α-diketones do not undergo polarity reversal in the presence of (benzo)thiazolium carbenes but are engaged in a novel multicomponent reaction with water to efficiently give medicinally relevant 1,4-thiazin-3-one heterocycles. The umpolung reactivity of diaryl 1,2-diones, however, can be effectively triggered by different NHCs.
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Frey, Georg [Verfasser]. "Mechanistische Einblicke und die Einführung eines metallfreien Reduktionsmittels in die Titan(III)-katalysierte reduktive Umpolung von Carbonylverbindungen / Georg Frey." München : Verlag Dr. Hut, 2016. http://d-nb.info/1120763916/34.
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Jacquet, Olivier. "Réactions asymétriques catalysées par le palladium : contrôle des chimio-, régio- et stéréosélectivités." Paris 11, 2007. http://www.theses.fr/2007PA112181.
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Les travaux décrits dans ce manuscrit ont trait à l’étude des différentes sélectivités lors de réactions catalysées par des complexes de palladium. La première partie est consacrée à la réaction d’hydrophénylation asymétrique d’alcènes. Nous avons dans un premier temps évalué l’influence de ligands chiraux sur la chimio et l’énantiosélectivité de l’hydrophénylation d’un substrat achiral. Les ligands les plus efficaces ont ensuite été testés sur des substrats racémiques et énantiopurs afin d’évaluer leur influence sur le contrôle de la régiosélectivité. Dans la seconde partie nous étudions divers aspects de la réaction d’allylation palladocatalysée. Dans un premier temps nous étudions l’alkylation de deux acétates allyliques racémiques et énantiopursdans le but de contrôler la régiosélectivité de substitution par la chiralité des ligands ainsi que d’effectuer un transfert total de la pureté énantiomérique des substrats aux produits. Un modèle réactionnel a ensuite été utilisé dans le but d’évaluer le caractère mou ou dur des nucléophiles dans la réaction de substitution nucléophile de type Tsuji-Trost. Le même modèle a ensuite été utilisé dans le but d’obtenir des informations mécanistiques sur les réactions d’allylations nucléophiles. La dernière partie est consacrée à l’application de l’allylation électrophile pour l’obtention de composés énantiomériquement purs pouvant être un point de départ à la synthèse de produits synthétiquement très intéressants. Les deux stratégies sont l’utilisation de ligands chiraux et l’emploi de nucléophiles chiraux. Ce travail a fait l’objet d’une collaboration avec le Laboratoire de Synthèse et MéthodologieThe work described in this thesis deals with the study of selectivities in palladium complexes catalyzed reactions. The first part is a study of alkenes asymmetric hydrophenylation. We first studied the influence of chiral ligands on chemo and enantioselectivities of the asymmetric hydrophenylation of an achiral substrate. The most efficient ligands were the tested with racemic and enantiopure substrates in order to evaluate their influence on the control of the regioselctivity. In the second part we studied various aspects of palladium catalyzed allylations. We first studied the alkylation of two racemic and enantiopure allylic acetates in order to control the regioselectivity of the substitution by the chirality of the ligands. We also worked on the transfer of the substrate enantiomeric purity to the alkylated products. A reactionnal model has been employed in order to evaluate the softness or the hardness of several nucleophiles in the Tsuji-Trost reaction. The same model has been used in order to have mechanistic informations on nucleophilic allylations. The last part is devoted to the application of electrophilic allylation to obtain enantiomerically pure compounds that can be suitable starting material to the synthesis of very interesting synthetically products. The two strategies were the use of chiral ligands or chiral nucleophiles. This work was carried out with the Laboratoire de Synthèse et Méthodologie
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Tomakinian, Terry. "Nouvelles méthodes de synthèse de benzofuroindolines. Vers la synthèse de la phalarine." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLS031.
Full textAbstract:
Les benzofuroindolines forment une famille de composés qui se retrouvent sous deux formes : les benzofuro[2,3-b]indolines ou les benzofuro[3,2-b]indolines. Ce motif se retrouve dans de nombreuses molécules naturelles comme la bipleiophylline, la voacalgine A, le diazonamide A et la phalarine ce qui a mené à de nombreuses recherches pour leur synthèse. La biogénèse postulée est le couplage oxydant d'un indole et d'un phénol. Nous avons développé plusieurs voies d'accès à ces motifs en utilisant le noyau indolique. La première étude a consisté en un couplage oxydant direct entre un N-acétylindole et un phénol en présence de FeCl₃ et de DDQ. La méthodologie a montré sa généralité sur des dérivés d'indoles N-acétylés pour former en une seule étape des benzofuro[3,2-b]indolines. Dans certains cas, la benzofuro[2,3-b]indoline est obtenue si les groupements fonctionnels en position 2 et 3 sur l'indole sont identiques. Dans un but de synthétiser la phalarine, unique molécule naturelle contenant un motif benzofuro[3,2-b]indoline, nous avons réalisé une étape de C2-arylation d'un indole par un phénol à l'aide d'un couplage pallado-catalysé. La cyclisation à l'aide de NIS permet d'obtenir la benzofuro[3,2-b]indoline. L'ajout du carbone manquant de l'un des cycles est en cours d'étude par ajout d'un nucléophile monocarboné possédant un groupement partant. Par ailleurs, une dernière voie d'accès aux benzofuro[3,2-b]indolines a pu été mise au point par une réaction de Fischer interrompue. La réaction entre des benzofuran-3-ones et des arylhydrazines dans des conditions acides conduit aux benzofuroindolines souhaitées sous forme d'hémiacétals. La méthode a montré sa généralité et sa robustesse. Finalement, réaliser l'Umpolung de l'indole est un défi intéressant pour additionner des nucléophiles en position 3 de l'indole. Pour cela, des N-hydroxyindoles ont été synthétisés et l'utilisation de sels de biaryliodonium triflate a permis de réaliser une O-arylation. Le produit formé étant instable, il subit un réarrangement sigmatropique [3,3] pour conduire aux benzofuro[2,3-b]indolines désiréesBenzofuroindolines are a family of compounds which can be found in two regioisomeric forms: benzofuro[2,3-b]indolines or benzofuro[3,2-b]indolines. This core is present in several natural products such as bipleiophylline, voacalgine A, diazonamide A or phalarine which have been the subject of intensive efforts towards their syntheses. The postulated biogenesis is the oxidative coupling of an indole and a phenol. We developed four pathways to access these structures using the indole nucleus.The first part consisted in a direct oxidative coupling between a N-acetylindole and a phenol in presence of FeCl₃ and DDQ. This strategy showed its generality on N-acetylindoles derivatives to form in only one step the benzofuro[3,2-b]indoline core. In some cases, the benzofuro[2,3-b]indoline is obtained if the substitution in the C-2 and C-3 position is the same. In order to synthesize the phalarine, the unique natural product to possess a benzofuro[3,2-b]indoline core, we designed a C-2 arylation of an indole with a phenol using a palladium-catalyzed coupling. The cyclization steps using NIS led to the benzofuro[3,2-b]indoline core. The insertion of the missing carbon of one of the rings is under study by adding a nucleophile which contains only one carbon and a leaving group. The last strategy to access to benzofuro[3,2-b]indolines has been focused on an interrupted Fischer indolization. The reaction between benzofuran-3-ones and arylhydrazines in acidic conditions led to the desired benzofuro[3,2-b]indolines. This methodology is general and robust. Another part of the project was to achieve the Umpolung of the indole to add nucleophiles in C-3 position of the indole nucleus. N-hydroxyindoles were synthesized and the use of biaryliodonium triflate salts allowed an O-arylation reaction. The product being unstable, a [3,3] sigmatropic rearrangement can take place to afford the desired benzofuro[2,3-b]indolines
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Desvergnes, Stéphanie. "Umpolung de nitrone induit par le diiodure de samarium (II) : application à la synthèse d'iminosucres, synthèse totale de la (+ )-hyacinthacine A2." Université Joseph Fourier (Grenoble), 2006. http://www.theses.fr/2006GRE10200.
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Pour montrer l'intérêt de l'Umpolung de nitrone induit par Sm12, une voie de synthèse générale d'iminosucres a été proposée par couplage réducteur avec une nitrone dérivée de sucre. Selon cette approche, la synthèse totale de la (+)-hyacinthacine A2 et une synthèse formelle de la (+ )-1-désoxycastanospermine ont été réalisées. Dans le but de développer cette nouvelle réaction et d'en étudier les limites, différents accepteurs de type Michael ont été testés avec des nitrones simples ou cycliques. Finalement, la transformation de diverses nitrones dérivées de sucres en iminosucres a été étudiée. Notamment, une nouvelle méthode de déprotection d'éthers benzyliques et d'acétals par le trichlorure de bore a permis de préparer des nitrones cycliques polyhydroxylées, dérivées de sucres. L'activité biologique des iminosucres synthétisés a été évaluée sur plusieurs ciblesTo highlight the interest of the nitrone Umpolung induced by Sm12, a general approach for the synthesis of iminosugars is proposed involving a reductive coupling with sugar-derived nitrones. This approach was used in the total synthesis of the (+)-hyacinthacine A2 and in a formai synthesis of the (+ )-1-deoxycastanospermine. With the aim to develop this new reaction and to study its limits, different Michael acceptors were reacted with simple and cyclic nitrones in presence of Sml20 Finally, the transformation of different sugar-derived nitrones into iminosugars was studied. Noteworthy, a new method was proposed for the deprotection of benzylic ethers and acetals with boron trichloride and it permitted the preparation of cyclic polyhydroxylated sugar-derived nitrones. The biological activity of the synthesised iminosugars was evaluated on different targets
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Eymur, Serkan. "Development Of Novel Catalytic Methodologies For Carboncarbon Bond Construction." Phd thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12615303/index.pdf.
Full textAbstract:
Addition reactions of nucleophilic trifluoromethyltrimethylsilane (CF3TMS) to acyl phosphonates were investigated. Various acyl phosphonates reacted readily with CF3TMS in the presence of K2CO3 to give 1-alkyl-2,2,2-trifluoro-1-trimethylsilyloxyethylphosphonate in 70-90% yields. When benzoyl phosphonates were used as starting material, after addition of CF3, the formed alcoholate undergoes phosphonatephosphate rearrangement to form the acyl anion, followed by elimination of F- to give 1-aryldifluoroethenyl phosphates in 87-97% yields.
The proline&ndashthiourea host&ndash
guest complex catalyzed intermolecular aldol reaction of aromatic aldehydes with cyclohexanone is developed. The anti-configured products were obtained in high yields and exclusively excellent nantioselectivities. The reaction is proposed to proceed according to a modified Houk&ndash
List model, in which the carboxylate moiety of the proline forms an assembly with the thiourea. These results clearly demonstrate the enormous effect of the thiourea on the reactivity and selectivity, even in an unconventional non-polar reaction medium, without the need to use low temperatures. A proline&ndash
thiourea host&ndash
guest complex is described as a good catalyst for the enantioselective nitro-Michael addition of aldehydes to nitroalkenes. The reaction is efficient with 5% of the thiourea, to give moderate to good enantioselectivity (up to 76% ee). High syn-selectivity was obtained with both branched and unbranched aliphatic aldehydes. This is the first example of self-assembly of organocatalysts with an achiral additive in a Michael addition wherein aldehydes are utilized as donors. An aldol reaction catalyzed by a proline&ndash
thiourea host&ndash
guest complex in a nonpolar solvent shows excellent nonlinear effects. This proline&ndash
thiourea system has the ability to form a hydrogen-bonding network. The enantiomeric excess of proline in a solution can be significantly enhanced by its incorporation with a urea molecule into its solid racemate. This suggests a general and facile route to homochirality, which may be involved in the origin of chirality on earth.
17
Luu, Hieu Trinh [Verfasser]. "Über die Anwendung der Titan(III)-katalysierten, reduktiven Umpolung in der Synthese von Erythrinaalkaloiden und Studien zur asymmetrischen Reaktionsführung / Hieu Trinh Luu." München : Verlag Dr. Hut, 2017. http://d-nb.info/1137024097/34.
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Luu, Hieu-Trinh [Verfasser]. "Über die Anwendung der Titan(III)-katalysierten, reduktiven Umpolung in der Synthese von Erythrinaalkaloiden und Studien zur asymmetrischen Reaktionsführung / Hieu Trinh Luu." München : Verlag Dr. Hut, 2017. http://nbn-resolving.de/urn:nbn:de:101:1-201707202211.
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Flahaut, Alexandre. "Utilisation de complexes carbènes N-hétérocyclique-palladium dans la réaction de Tsuji-Trost et dans la réaction umpolung d'allylation de dérivés carbonylés." Paris 6, 2008. http://www.theses.fr/2008PA066149.
Full textAbstract:
Nous avons décrit la synthèse d’une nouvelle famille de ligand NHC-N chiraux bidentates et leur utilisation dans la réaction de Tsuji-Trost. Ces ligands ont été facilement obtenus à partir des sels amino-imidazolium chiraux correspondants synthétisés à partir de sels oxo-imidazoliums sur lesquels la chiralité a été introduite par une réaction de formation d’une imine avec des amines chirales. Une réduction diastéréosélective a permis un accès efficace aux sels amino-imidazoliums. Les complexes NHC-amino et imino des métaux de transition ont été obtenus par traitement des sels imidazoliums avec de l’oxyde d’argent puis transfert des ligands NHC sur des complexes du palladium, du cuivre et du rhodium. Les propriétés complexantes des ligands NHC-amino sur le palladium ont été démontrées par analyse RX. Ils ont été testés via un complexe NHC-amino-argent, obtenu sous forme d’un mélange de diastéréoisoméres, dans la réaction d’alkylation du 1,3-diphényl-allyl-acétate par l’anion du malonate. Des excès énantiomériques, en faveur de l’énantiomère (R), allant jusqu’à 80% ont été obtenus. Un nouveau système catalytique très actif a été développé en version achirale à l’aide de complexes (NHC)(phosphine)palladium généré in-situ. Des conversions totales ont été obtenues en moins de 5 minutes. Le système a été étendu à une réaction d’amination. Une réaction umpolung d’allylation de dérivés carbonylés en présence d’Et2Zn et de différents acétates allyliques, a été mise au point à partir de ces mêmes complexes mixtes. Ce système conduit à des rendements élevés et à une gestion de la régiosélectivité dans la plupart des cas > 98/02 et à une diastéréosélectivité anti allant jusqu’à 92/8. Ce système est inefficace avec les imines. L’influence du solvant a été étudiée : les conversions sont améliorées dans le CH2Cl2, tandis que la diastéréosélectivité est meilleure dans l’éther.
20
Woertink, Jason Kyle. "Studies of phosphine catalyzed umpolung reactions, ruthenium and rhodium catalyzed vinylidene addition reactions and progress towards the total synthesis of didemnaketal A /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Reis, Omer. "Development Of Acyl Anion Precursors And Their Applications." Phd thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/3/12605950/index.pdf.
Full textAbstract:
This thesis presents the development of new acyl anion precursors and their applications. The main concern of this thesis was to make use of acyl anion precursors in catalytic bond forming reactions. Toward this aim, previously known cyanide ion catalyzed cleavage of benzils was investigated in scope and efficiency in unsymmetrical benzoin condensation. Although benzils were proved to be useful entities as acyl anion precursors in benzoin condensation, they suffer some major drawbacks. Therefore acylphosphonates were proposed and investigated as a new generation of acyl anion precursor. They were found to be highly versatile and efficient in both catalytic unsymmetrical benzoin synthesis and other useful transformations.
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Klimczyk, Sebastian [Verfasser], Nuno [Gutachter] Maulide, and Gerald [Gutachter] Dyker. "Sulphoxide-mediated umpolung of alkali halides and gold(I)-catalysed cyclopropanation of sulphonium ylides / Sebastian Klimczyk ; Gutachter: Nuno Maulide, Gerald Dyker ; Fakultät für Chemie und Biochemie." Bochum : Ruhr-Universität Bochum, 2015. http://d-nb.info/1228624313/34.
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Reis, Barbaros. "Addition Of Acyl Phosphonates To Ethylcyanoformate." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/2/12609090/index.pdf.
Full textAbstract:
Functionalized cyanophosphates are important starting materials for the synthesis of
beta-lactam ring moiety of beta-lactam antibiotics. The cyanophosphates are
synthesized starting from easily available acylphosphonate and ethylcyanoformate.
Acylphosphonates are synthesized starting from acylchloride and trimethylphosphite.
Addition of acylphoshonate to ethylcyanoformate furnishes the cyanophosphate with
the quaternary center.
24
Averesch, Kai Florian Gustav. "Novel Cationic Sulfur Reagents and their Application in Electrophilic Group-Transfer Reactions." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2019. http://hdl.handle.net/21.11130/00-1735-0000-0005-13C9-3.
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Esiringu, Ilker. "Intermolecular Addition Of Aldehydes To Ketones Via Acyl Phosphonates." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12609441/index.pdf.
Full textAbstract:
This thesis presents a new developed method for first intermolecular aldehyde/ketone cross benzoin coupling. Protected α
-keto tertiary alcohols are synthesized starting from easily available acyl phosphonates and ketones via Brook rearrangement in the presence of catalytic amount of cyanide ion. The scopes and the limitations of the methods for the synthesis of tertiary alcohols with &
#945
-keto group are discovered.
26
Hirner, Sebastian. "New Methodologies in Organic Chemistry: Applications to the Synthesis of α-Amino Acids and Natural Products." Doctoral thesis, KTH, Organisk kemi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11112.
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This thesis deals with the development and application of new synthetic methodology in organic chemistry. The first part describes the development of a new protocol for the synthesis of 3-pyrrolines by means of a microwave-assisted ring-expansion reaction of 2-vinylaziridines. In addition, this methodology is implemented as a key-step in a formal total synthesis of the antibiotic (-)-anisomycin. In the second part, a new methodology for the synthesis of arylglycines from Weinreb amides is described. In this procedure, a Grignard reagent is added to the iminium ion formed from the Weinreb amide upon treatment with a base. When a chiral amide is used, the nucleophilic addition proceeds with high diastereoselectivity. Finally, an easy and straightforward synthesis of α-amino amides via a base-mediated rearrangement of modified Weinreb amides into N,O-acetals is presented. Subsequent arylation, alkylation, alkenylation or alkynylation of this intermediate affords the corresponding α-amino amides in excellent yields. Furthermore, a more generalized protocol for the α-arylation of Weinreb amides lacking an α-amino moiety is also discussed.QC 20100719
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Klare, Helge [Verfasser]. "Entwicklung Phosphorbasierter Umpolungs- und Wasserstoffbrücken-Katalysatoren / Helge Klare." München : Verlag Dr. Hut, 2015. http://d-nb.info/1070124206/34.
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Nocquet-Thibault, Sophie. "La difonctionnalisation d’énamides en utilisant des dérivés d’iode (III) hypervalent." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112270/document.
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Lors de ce travail de thèse qui visait à développer une méthode générale d’introduction d’halogénures et de pseudo-halogénures en se basant sur l’utilisation de réactifs d’iode hypervalent en tant que promoteurs d’umpolung, diverses avancées ont pu être accomplies. Tout d’abord, une réaction d'alkoxybromation régiosélective mettant en jeu des sels de bromure et du PIDA a été mise au point. Un des intérêts de cette réaction réside dans l'utilisation de LiBr peu coûteux comme source d'halogène électrophile (par inversion de polarité : umpolung). En outre, l'introduction de deux groupements de manière chimio- et régiosélective est possible sans recourir à l'utilisation d’un catalyseur métallique. Une large gamme d'énamides a été testée et les rendements sont généralement excellents (au dessus de 75 %) et les réactions rapides (moins d’une heure). En outre, la diastéréosélectivité oscille entre modérée et excellente. Ces produits éthoxybromés se sont aussi montrés très polyvalents et permettent l’accès à de nombreux motifs structuraux. Une version asymétrique de cette réaction en faisant intervenir des dérivés d’iode hypervalent chiraux n’a pas été couronnée de succès tout comme l’introduction de copules chirales. Le but initial était de mettre au point une méthode générale de difonctionnalisation d’énamides avec l’insertion d’halogénures. C’est pourquoi, notre stratégie a ensuite été étendue au chlore et une réaction d’éthoxychloration a été développée avec des rendements moyens à très bons (de 36% à 86%) un temps de réaction rapide (généralement autour de 30 minutes) et une diastéréosélectivité moyenne à très bonne (de 55/45 à 92/8). Les deux réactions d’éthoxybromation et d’éthoxychloration ont fait l’objet d’une investigation mécanistique (notamment par spectrométrie de masse) et il semblerait que le mécanisme soit ionique. Nous avons alors voulu appliquer cette méthodologie au fluor, élément dont l’introduction sélective sur un substrat est rarement triviale. En accord avec la littérature, nous avons conclu que le fluor ne pouvait être transféré directement en tant qu’électrophile. Enfin, une version d’éthoxyiodation a été validée et est en cours d’optimisation au laboratoire. Concernant les pseudo-halogénures, nous nous sommes uniquement intéressés aux azotures. Ayant réalisé qu’une réaction d’éthoxyazidation ne serait pas possible, une étude poussée des différents paramètres réactionnels adossée à la compréhension des mécanismes mis en jeu a été entreprise. Deux méthodologies ont alors pu être mises au point : une réaction de diazidation dont les rendements sont modérés ( entre 20% et 52%), les temps de réaction courts (environ 1 h) et des diastéréosélectivités moyennes à bonnes (entre 75/25 et 90/10) ainsi qu’une réaction d’oxyamination qui se montre bien plus efficace avec des rendements moyens à très bons (de 31% à 95%), des temps de réaction assez rapides (autour de 2 h), des diastéréosélectivités souvent excellentes (supérieures à 67/33) et un champ d’application bien plus large (Schéma 245). Ces deux méthodes réunies représentent un outil utile pour l’obtention de composés à la fois azotés et azidés. Dans ce cas, les intermédiaires réactionnels semblent être radicalaires même si des études complémentaires restent à effectuer.L’intérêt synthétique de ces deux types de composés a aussi fait l’objet de diverses études. Si la réduction du groupement azido en amine n’a pas pu être systématiquement accomplie, des réactions de cyclisation d’Huisgen sur les produits diazidés ont cependant fonctionné (les produits oxyaminés semblant trop encombrés stériquement). Quant au groupement TEMPO il a notamment pu être oxydé en cétone. Ainsi, des outils méthodologiques ont été développés lors de cette thèse, pour la difonctionnalisation oxydante d’énamides par des dérivés d’iode (III) hypervalent et en particulier, l’introduction d’halogénures et d’azoturesHypervalent iodine compounds such as (diacetoxyiodo)benzene (PIDA) are non-toxic and mild reagents that can behave in similar fashion to transition-metal complexes. Indeed, around the central iodine atom, ligands can be exchanged and then transferred through a formal reductive elimination. Following this strategy, halides can be used as ‘ligands’, in which case an umpolung of the salt can occur to give birth to electrophilic halogen species. Using LiBr, ethanol and PIDA, a variety of enamides underwent a regioselective ethoxybromination with high yields, short reaction time and good to excellent diastereoselectivity. One of the main interests of this reaction lies in the use of a cheap and widely available bromide salt (LiBr) to generate electrophilic halogen species by umpolung. Moreover, despite the oxidative nature of the reaction conditions, a wide scope of functional groups (olefins, esters, alcohols…) is tolerated. This reaction provides α-bromo-hemiaminals which are highly versatile synthons. For instance, various nucleophiles can be incorporated on the hemiaminal moeity and then engaged in further transformations. The development of an asymmetric variant of this transformation using chiral pool or chiral hypervalent iodine was unsucceful. This methodoly has been extended to the umpolung of other salts as chlorine with moderate to good yields (from 36% to 86%) and a moderate to very good diastereoselectivity (from 55/45 to 92/8) with a short reaction time (30 minutes). Mechanistic investigation for both reactions has been performed and an ionic parthway has been priviledge. The introduction of fluorine as an electrophile was not possible according to the litterature.Finally, the last halide, iodine can be tansfered and an ethoxyiodation reaction is under optimisation. Concerning the pseudo-halides, we devot a special attention to azides. Two methodologies has been set up : a diazidation reaction which yields are moderate (betwwen 20% and 52%), short reaction times (around 1 h) and moderate to good diastereoselectivity ratios (between 75/25 and 90/10) and an oxyamination reaction whiwh shows to be much more efficient with moderate to very high yields (from 31% to 95%), short reaction times (around 2 h), excellent diastereoselectivity ratio (superior to67/33). These two gathered reactions represent a useful tool for the introduction of a nitrogen. For the diazidation reaction, the intermediatories seem to be radicals whereas for the oxyamination reaction probably ionic species. . Thus, synthetic tools have been developped during this thesis for the difunctionnalisation of enamides by hypervalent iodine and particulary introduction of halides and azides
29
Bonito, Oliva Valeria. "Diffusion de silicium et dopage de type n dans le AlN." Electronic Thesis or Diss., Université Côte d'Azur, 2024. https://intranet-theses.unice.fr/2024COAZ5009.
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Dans cette thèse, nous menons une étude approfondie de la diffusion du silicium (Si) dans le nitrure d'aluminium (AlN) massif et dans de l'AlN épitaxé sur substrat saphir.Nous introduisons le Si dans l'AlN à partir d'une couche de de Si1-xNx amorphe déposée par pulvérisation réactive. Notre étude concerne des recuits thermiques effectués à des températures comprises entre 1500 et 1700°C, avec des durées variant de 1 à 4 heures. En utilisant des techniques analytiques avancées telles que la spectrométrie de masse à ions secondaires (SIMS), la spectroscopie de rayons X à dispersion d'énergie (EDX) et la microscopie électronique à transmission (TEM), nous étudions les changements structuraux et de composition induits par les recuits à haute température, ce qui permet de comprendre les mécanismes de diffusion du Si dans l'AlN.L'étude des paramètres de diffusion fondamentaux est rendue possible grâce à une analyse de la diffusion du Si dans des cristaux d'AlN massifs à faible densité de dislocation. Nos expériences révèlent des profils de diffusion convexes sous forme de boite, caractérisés par un coefficient de diffusion dépendant de la concentration. En intégrant nos résultats expérimentaux aux modèles théoriques existants, nous établissons que la diffusion du Si dans l'AlN se fait par l'intermédiaire de paires dopant-lacunes chargées négativement. Le coefficient de diffusion intrinsèque présente un comportement dépendant de la température avec une enthalpie d'activation de 10.34 eV.Dans la deuxième partie de ce travail, nous nous concentrons sur l'étude de l'impact de la diffusion des impuretés de Si et d'oxygène (O) dans les couches d'AlN épitaxiées sur substrat saphir. Notre étude montre la formation d'inversions de polarité dans l'AlN suite aux recuits haute température. L'inclusion d'impuretés Si et O s'avère essentielle pour leur formation et leur stabilisation. Selon le modèle que nous proposons, une forte concentration de complexes impureté-lacune affecte la stabilité du réseau cristallin, ce qui conduit aux inversions de polarité observées après recuit. Notre hypothèse est que la présence d'impuretés Si facilite la formation d'accepteurs tels que des lacunes de N, favorisant la précipitation d'O et permettant ainsi la formation des inversions de polaritéIn this dissertation, we conduct an in-depth investigation on the diffusion behavior of silicon (Si) in both bulk aluminum nitride (AlN) and epitaxial AlN grown on sapphire substrates. We introduce Si into AlN using reactive sputtering to deposit amorphous Si1-xNx onto AlN, which serves as the Si source. Our investigation includes thermal annealing conducted at temperatures between 1500 and 1700°C, with durations varying from 1 to 4 h. Employing advanced analytical techniques such as secondary ion mass spectrometry (SIMS), energy-dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM), we study the structural and compositional changes induced by the high-temperature annealing, unraveling the diffusion mechanisms of Si in AlN.The exploration of fundamental diffusion parameters becomes feasible through the analysis of Si diffusion in low dislocation density bulk AlN crystals. Our diffusion experiments reveal distinctive convex box-like diffusion profiles, characterized by a concentration-dependent diffusion coefficient. By integrating experimental results with existing theoretical calculations, we find that Si diffusion in AlN is mediated by singly negatively charged dopant-vacancy pairs. The intrinsic diffusion coefficient exhibits a temperature-dependent behavior with an activation enthalpy of 10.34 eV.In the second part of this work, we shift our focus to investigating the impact of Si and oxygen (O) impurity diffusion in epitaxial AlN layers grown on sapphire substrates. Our investigation reveals the formation of polarity inversions in AlN resulting from high-temperature annealing. The presence of both Si and O impurities is crucial for the formation and stabilization of these polarity inversions. Our model proposes that increased concentrations of impurity-vacancy clusters within the AlN structure exerts an influence on the stability of the crystal lattice, culminating in the observed polarity inversions after annealing. Si impurities are hypothesized to play a crucial role in facilitating the formation of N-vacancies, thus promoting O precipitation and, ultimately, enabling the polarity inversions
In dieser Dissertation wird das Diffusionsverhalten von Silizium (Si) in Aluminiumnitrid (AlN) und epitaktischem AlN, das auf Saphirsubstraten gewachsen ist, grundlegend untersucht. Wir scheiden amorphes Si1-xNx durch reaktives Sputtern auf AlN ab, das als Si-Quelle dient. Unsere Untersuchung umfasst thermisches Glühen bei Temperaturen zwischen 1500 und 1700 °C mit einer Dauer von 1 bis 4 Stunden. Mit Hilfe fortgeschrittener Analysetechniken wie Sekundärionen-Massenspektrometrie (SIMS), energiedispersiver Röntgenspektroskopie (EDX) und Transmissionselektronenmikroskopie (TEM) untersuchen wir die strukturellen und kompositorischen Veränderungen, die durch das Hochtemperaturglühen hervorgerufen werden, und untersuchen die komplexen Diffusionsmechanismen von Si in AlN. Die Erforschung grundlegender Diffusionsparameter wird durch eine Analyse der Si-Diffusion in AlN-Kristallen mit geringer Versetzungsdichte möglich. Unsere Diffusionsexperimente zeigen ausgeprägte konvexe kastenförmige Diffusionsprofile, die durch einen konzentrationsabhängigen Diffusionskoeffizienten gekennzeichnet sind. Durch die Integration der experimentellen Ergebnisse mit bestehenden theoretischen Berechnungen stellen wir fest, dass die Si-Diffusion in AlN durch einfach negativ geladene Dotierstoff-Leerstellenpaare vermittelt wird. Der intrinsische Diffusionskoeffizient weist ein temperaturabhängiges Verhalten mit einer Aktivierungsenthalpie von 10.34 eV auf. Im zweiten Teil dieser Arbeit konzentrieren wir uns auf die Untersuchung der Auswirkungen der Diffusion von Si- und Sauerstoffverunreinigungen in epitaktischen AlN-Schichten, die auf Saphirsubstraten gewachsen sind. Unsere Untersuchung zeigt die Bildung von Polaritätsinversionen in AlN als Folge von Hochtemperaturglühen. Dabei finden wir, dass Si- und O-Verunreinigungen entscheidend für deren Bildung und Stabilisierung sind. Unser Modell geht davon aus, dass erhöhte Konzentrationen von Verunreinigungs-Leerstellen-Clustern in 6 der AlN-Struktur die Stabilität des Kristallgitters beeinträchtigen, was zu den beobachteten Polaritätsumkehrungen nach dem Glühen führt. Die wesentliche Annahme für den beobacheten Mechanismus ist, dass Si-Donatoren zur Bildung von akzeptorischen N-Leerstellen beitragen, die Ausscheidung von O fördern und so die Polaritätsumkehrungen ermöglichen
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Klare, Helge [Verfasser], Bernd [Gutachter] Goldfuss, and Axel [Gutachter] Griesbeck. "Entwicklung Phosphorbasierter Umpolungs- und Wasserstoffbrücken-Katalysatoren / Helge Klare ; Gutachter: Bernd Goldfuss, Axel Griesbeck." Köln : Universitäts- und Stadtbibliothek Köln, 2015. http://d-nb.info/1231433329/34.
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Rose, Marcus, Andreas Notzon, Maja Heitbaum, Georg Nickerl, Silvia Paasch, Eike Brunner, Frank Glorius, and Stefan Kaskel. "N-Heterocyclic carbene containing element organic frameworks as heterogeneous organocatalysts." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-138636.
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A bifunctional imidazolium linker was used for the production of highly crosslinked element organic frameworks by Suzuki-coupling with tetrafunctional boronic acids. The resulting porous materials are good heterogeneous organocatalysts in the N-heterocyclic carbene-catalyzed conjugated umpolung of α,β-unsaturated cinnamaldehydeDieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich
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Ruffoni, A. "SYNTHESIS OF NEW CONFORMATIONALLY CONSTRAINED BETA-SULFANYL-ALFA- AMINO ACIDS AND THEIR EXPLOITATION IN THE SYNTHESIS OF PEPTIDOMIMETICS." Doctoral thesis, Università degli Studi di Milano, 2014. http://hdl.handle.net/2434/232418.
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Considering the great interest in the field of peptidomimetics and the potentiality of the norbornene scaffold, this thesis has been primarily devoted to the synthesis and exploitation a of new class of β-substituted norbornene amino acids as cysteine mimics. The project has been developed with the aim to fill the gap unexpectedly present in the literature in this field and to confirm the unexploited properties of norbornene amino acid as potential building block for peptidomimetics synthesis. At first, we followed the purpose to individuate a novel synthetic strategy to obtain, not only simple but also highly functionalized, norbornene scaffold in grams scale synthesis, in order to make possible further developments in this field and interesting practical applications. Subsequently, we set out to design, realize and conformationally analyze model peptides containing norbornene amino acids in order to demonstrate the ability of such compounds to behave as strong inducers of helical structure and the possibility to be used in the synthesis of unnatural peptides of therapeutic interest. Finally, we explored the field of small molecules as peptidomimetics and demonstrated the advantage of rigid core in the development of new drugs. To do this, we planned to design and realise new chemical entities based on an extensively modified norbornene scaffold which have shown high activity in modulation of Rac1-Tiam1 protein-protein interactions resulting in a new class of potent inhibitors.. During the synthesis of such molecules we also launched a study aiming to better understand which kind of effects a constrained chemical structure, as norbornene scaffold, could have on the regiochemistry in palladium chemistry, imposing a methodic analysis of the steric and electronic effects in the reaction mechanisms.
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Rose, Marcus, Andreas Notzon, Maja Heitbaum, Georg Nickerl, Silvia Paasch, Eike Brunner, Frank Glorius, and Stefan Kaskel. "N-Heterocyclic carbene containing element organic frameworks as heterogeneous organocatalysts." Royal Society of Chemistry, 2011. https://tud.qucosa.de/id/qucosa%3A27766.
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A bifunctional imidazolium linker was used for the production of highly crosslinked element organic frameworks by Suzuki-coupling with tetrafunctional boronic acids. The resulting porous materials are good heterogeneous organocatalysts in the N-heterocyclic carbene-catalyzed conjugated umpolung of α,β-unsaturated cinnamaldehyde.Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
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Beaud, Rodolphe. "Hydroarylation régiosélective d’indoles pour l’accès aux motifs 3 - arylindolines : études et applications d’une nouvelle réactivité de l’indole." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112308/document.
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Le diazonamide A, molécule naturelle extraite d’une ascidie marine, présente une activité antitumorale très importante (IC₅₀ < 5 nM) selon un mode d’action tout à fait original. Des études ont en effet prouvé que cette molécule inhibait une enzyme, l’Ornithine-d-aminotransferase, intervenant dans la réplication cellulaire des cellules cancéreuses faisant d’elle un poison du fuseau mitotique très sélectif. Cette molécule présente en son sein un cœur benzofuroindoline qui serait issu, d’un point de vue biogénétique, d’un couplage oxydant entre un noyau indole et un noyau phénol. Afin de développer une méthode générale de synthèse d’analogues simplifiés du diazonamide A, nous avons mis au point une voie d’accès efficace et simple au noyau benzofuroindoline. Ce projet nous a permis de mettre en place une stratégie en 3 étapes à partir d’indoles acétylés et de phénols qui permettent l’obtention de benzofuroindolines. La première étape est une réaction d’hydroarylation sur la double liaison C₂-C₃ de l’indole médiée par le trichlorure de fer. Cette première étape met en avant une réactivité tout à fait inhabituelle du noyau indole en rendant la position 3 de cet hétérocycle, électrophile. Grâce à cette stratégie, nous avons pu obtenir une librairie importante de benzofuroindolines dont certaines présentent une activité biologique encourageante. La seconde partie de ces travaux de thèse ont porté sur une étude plus approfondie de la réaction d’hydroarylation de l’indole. Une étude intensive du champ d’application de cette réaction ont permis de mettre en avant une haute tolérance de groupements fonctionnels. De plus l’étude des nucléophiles aromatiques tels que des polyaromatiques ou des hétérocycles ont permis d’obtenir un grand nombre de 3-arylindolines avec une diversité structurale très importante. Ces travaux ayant porté sur l’umpolung de l’indole, des études mécanistiques ont finalement été menées afin d’expliquer cette réactivité. Des études de marquage isotopique, d’infra-rouge in-situ ainsi que l’établissement d’une relation de Hammett ont permis de proposer un mécanisme réactionnel plausibleThe benzofuroindoline core is a unique motif found in the natural products diazonamide A bipleiophylline and azonazine. From a biosynthetic point of view, we can assume that the benzofuroindoline skeleton arises from the oxidative coupling of an indole and a phenol.The benzofuroindoline motif represents an opportunity for the discovery of new antitumor agents. Diazonamide A is a very potent anticancer agent that has received considerable attention owing to its high antitumor activity (IC₅₀ < 5nm) and its unique mode of action the inhibition of a newly discovered role for the ornithine-δ-aminotransferase. It is suggested that this natural product may have clinical utility for cancer therapy because it is as active in vitro as widely used antimitotic drugs such as taxanes and vinca alkaloids, but does not have their toxicity in normal dividing tissue. Owing to the high potential of diazonamide A and its scarce availability, it is highly desirable to identify simplified benzofuroindoline analogues as promising as the natural product, but more synthetically accessible.We report herein the C3-regioselective hydroarylation of N-acetyl indoles with phenols mediated by FeCl ₃ featuring a rare example of the electrophilic reactivity of the indole core in a Friedel–Crafts reaction. The indole Umpolung, followed by an oxidation step, allows us direct access to the tetracyclic benzofuroindoline motif found in the natural product diazonamide A.Moreover, this activation of N-acetylindoles with iron(III) chloride allows the C-H addition of other aromatic substrates than phenols to the C ₃ =C₂ double bond of the indole nucleus generating a quaternary center at C ₃ and leading regioselectively to 3-arylated indolines. Optimization, scope, practicability (gram scale, air atmosphere, room temperature) and mechanistic insights of this process are presented in this study
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Ciccolini, Cecilia. "Synthesis of Mono and Poly-Heterocycles starting from 1,2-Diaza-1,3-Dienes (or precursors) as Building Blocks." Doctoral thesis, Urbino, 2020. http://hdl.handle.net/11576/2674162.
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Gromovyi, Maksym. "Génération de seconde harmonique dans des guides d’ondes à base de nitrure d’éléments III." Thesis, Université Côte d'Azur (ComUE), 2018. http://www.theses.fr/2018AZUR4018/document.
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Ce travail est consacré à l’étude de la génération de deuxième harmonique (SHG) dans des guides d’ondes de Nitrure d’éléments III. Un des buts principaux de ce travail, était d’identifier les origines des pertes à la propagation dans les guides d’ondes GaN et de fortement les réduire dans des guides présentant des possibilités d’accord de phase, pour améliorer l’efficacité de la SHG. Nous avons fait un progrès très important dans cette direction et avons fabriqué des guides d’ondes plans de GaN épitaxiés sur des substrats de saphir avec des pertes à la propagation inférieure à 1dB/cm dans le visible. Dans ces guides d’ondes à faibles pertes, il a été possible d’obtenir un processus de SHG efficace en utilisant l’accord de phase modal. Nous avons obtenu 2% de conversion entre une pompe dans le proche infrarouge et un harmonique dans le visible, ce qui correspond à une efficacité de conversion normalisée de 0,15%W-1cm-2. Les pertes à la propagation et l’efficacité de conversion obtenues sont les meilleurs résultats rapportés jusqu'ici pour des guides d’ondes plan en GaN. De plus, nous avons étudié des guides d’ondes de Nitrure d’éléments III épitaxiés sur des substrats de Si, dont la fabrication demande de relever plusieurs défis, mais qui ouvrent des possibilités intéressantes. La première est la possibilité de graver sélectivement les nitrures ou le Si, ce que nous avons utilisé pour développer une plate-forme permettant la fabrication d’objets suspendus comme des micro-disques, des guides d’ondes et des micro-disques couplés à un guide d’ondes. Cette plate-forme a permis la première démonstration de SHG doublement résonante en utilisant un accord de phase modal entre des modes de galerie du micro-disque. Bien que toutes les expériences que nous avons exécutées aient été faites dans une région spectrale limitée, l’étude numérique présentée dans ce manuscrit démontre la grande adaptabilité de cette plate-forme basée sur la possibilité de faire varier la composition des guides d’ondes AlGaN de GaN pur à AlN pur. La deuxième possibilité liée à l’épitaxie de nitrures d’éléments III sur Si, est qu'en la combinant avec des techniques de report, on peut jouer avec des guides nitrures d’éléments III sur SiO2. Nos résultats numériques révèlent le potentiel complet des guides d’ondes d’AlGaN en démontrant qu’en utilisant différentes combinaisons de mode et en jouant sur la composition et la géométrie des guides d’ondes, il est possible d’obtenir un signal de deuxième harmonique dans l’ultra-violet, le visible ou le proche-infrarouges. Ces résultats montrent aussi, que pour améliorer encore l’efficacité de la SHG, on doit fabriquer des guides d’ondes canaux présentant un isolement optique parfait du substrat de Si et une inversion de polarité précisément placée dans le cœur du guide d’ondes. Dans une telle structure on pourrait profiter simultanément du confinement de la puissance, de l’accord de phase modal et d’un recouvrement optimisé des modes en interaction. Dans ce cas, nos calculs montrent que l’efficacité de conversion pourrait atteindre 100%W-1cm-2. Au cours de ce travail nous avons pu tester des guides canaux et des guides présentant une inversion de polarité dans le cœur. La qualité des flancs des guides canaux s’est avérée être tout à fait encourageante, mais leur performance non linéaire sont restées très limitées, principalement à cause de fortes pertes à la propagation dues au couplage avec le substrat absorbant et à la forte rugosité de surface des couches inversées. Les structures utilisant les techniques de report, n'ont pu être testées car elles ont cassé en cour de fabrication. L'obtention de guides optimisés exige de progresser encore pour réaliser des couches de confinement optique plus épaisses et/ou d’adapter la technique de report à ces matériauxThis work is dedicated to the study of the second harmonic generation (SHG) in III-Nitride waveguides. One of the main goals of this work, was to identify the origins of the propagation losses in GaN waveguides, and to strongly reduce them in waveguides presenting some phase matching possibilities, in order to improve the SHG efficiency. We have made a very important progress in this direction, and fabricated by hetero-epitaxy GaN planar waveguides on sapphire substrates with propagation losses below 1dB/cm in the visible spectral region. These low-loss waveguides were used for the demonstration of an efficient second harmonic generation process using modal phase matching. We obtained 2% of power conversion from the near-infrared to the visible spectral regions with a normalized efficiency of 0.15%W-1cm-2. The obtained propagation losses and conversion efficiency are the best-reported results so far for GaN planar waveguides. In addition, we have studied epitaxial III-nitride waveguides on Si substrates, which are very challenging to fabricate, but opens new interesting opportunities. The first one is the possibility to etch selectively the nitrides or the Si. The selective chemical etching was used to develop a platform allowing the fabrication of suspended objects such as micro-disks, waveguides and micro-disks coupled to a waveguide. This platform has allowed the first demonstration of doubly resonant SHG using phase matching between the whispering gallery modes of a micro-disk. Although all the experiments we performed were done in a limited spectral region, the numerical study presented in this manuscript demonstrates the large adaptability of this platform based on the possibility of varying the composition of AlGaN waveguides from pure GaN to pure AlN. The second opportunity of epitaxial III-nitrides layers on Si is the possibility to combine them with report technologies to obtain III-nitride waveguides on SiO2. Our numerical results reveal the full potential of AlGaN waveguides by demonstrating that using different mode combinations and playing with waveguides composition and geometry, it is possible to obtain a second harmonic signal in the ultraviolet, the visible or the near-infrared spectral regions. These results also demonstrate, that to further improve the SHG efficiency, one has to fabricate ridge waveguides presenting a perfect optical isolation from the Si substrate and a polarity inversion precisely positioned in the core of the waveguide. In these structures one could benefit simultaneously from the power confinement, the modal phase matching and an optimized overlap of the interacting modes. In this case, we calculate that the conversion efficiencies could be as high as 100%W-1cm-2. Both ridge waveguides and polarity inversion were tested in this work. The quality of the ridges was quite encouraging, but their nonlinear performance remained limited mainly because of the high propagation losses due to the coupling with the absorbing substrate and to the roughness of the surface of the epitaxial inverted layers. The structures fabricated using the report technique, haven’t been tested, as they were broken during their fabrication. Getting fully optimized waveguides requires further progresses in realizing thicker optical buffer layers and/or adapting the report technique to these materials
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Huang, Yu-Kai, and 黃煜凱. "Synthesis of Furanone Derivatives via Umpolung by Organophosphanes." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/ujbpg3.
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碩士國立臺灣師範大學
化學系
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This thesis is divided into two parts: synthesis of furanone derivatives via umpolung by organophosphanes (part I) and investigation of phosphine-mediated direct β-acylation reactions: An efficient method for the synthesis of hex-4-en-1,3,6-trione derivatives (part II). Part I: We have developed an organophosphane-mediated cinnamic acid derivatives for synthesis of the ylide which contain ketene group in mild condition. In addition, the advantages of the reaction are one-pot, without reactants preparation. We accidentally obtain furanone derivatives.It is important for the development of versatile intermediates in organic synthesis. So we attempt to develop novel synthetic methods and valuable ketene intermediate in this part. Part II: Construction an acyl group at the electrophilic β position of α,β-unsaturated diketone derivatives by organophosphane has been achieved. The reaction condition is mild, metal free and could afford good yields.
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"NHC-catalyzed transformations: Stetter, benzoin, and ring expansion reactions." Thesis, 2012. http://hdl.handle.net/10388/ETD-2012-06-489.
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N-Hetereocyclic carbenes (NHC) have been intensively investigated since Ukai et al had reported the first NHC-catalyzed coupling of two equivalents of benzaldehyde, to form what is known as the benzoin product. A plethora of reports have since been published on NHC-catalyzed reactions, such as the cross-benzoin, Stetter, redox reactions, and many others. An attractive feature of NHCs is their ability to effect the umpolung (inversion of reactivity) of aldehydes. The efforts in the introduction of β,γ-unsaturated-α-ketoesters as acceptors for the Stetter reaction have led to the first highly enantioselective intermolecular Stetter reaction with β-aryl substituted Stetter acceptors (up to >99% ee). The synthetic applications of the Stetter adducts generated from the α-ketoester acceptors were demonstrated to give access to a diverse number of useful building blocks. Furthermore, the α-ketoester substrates were found to also be applicable for the cross-benzoin reaction. Through the development of a new electron-deficient, morpholine-based triazolium-derived carbene, a highly chemo- and enantioselective cross-benzoin reaction was achieved using aliphatic aldehydes and α-ketoesters. This methodology constitutes as the first highly enantioselective intermolecular cross-benzoin reaction with aliphatic aldehydes (up to 93% ee). In addition, a highly divergent synthesis of Stetter adducts and cross-benzoin products could be achieved in excellent regioselectivity.
Interested in utilizing NHCs as organocatalysts for the development of new reactions, tetrahydrofuran and prolinal derivatives were found to undergo efficient ring-expansions. This methodology gives access to highly functionalized lactones and lactams, which could serve as synthetically useful building blocks for the synthesis of natural products and biologically active compounds.
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Hatcher, John. "An Umpolung Approach to the α-Functionalization of Ketones and Aldehydes." Diss., 2011. http://hdl.handle.net/10161/5019.
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The α-alkylation of N-sulfonyl hydrazones via in situ-derived azoalkenes provides an umpolung approach to ketone α-alkylation that has considerable potential with regard to catalysis and the direct incorporation of functionality not amenable to the use of enolate chemistry. Herein, the first Cu(I)-catalyzed addition of Grignard reagents to in situ-derived N-sulfonyl azoalkenes is described. This method is remarkable in its ability to deliver highly sterically hindered compounds that would be difficult or impossible to synthesize via traditional enolate chemistry, including those having up to three contiguous quaternary centers. This method is compatible with a wide variety of α-halo tosylhydrazones, including cyclic and acyclic α-halo tosylhydrazones as well as those derived from both ketones and aldehydes. Also, herein, the first asymmetric organocatalytic sulfenylation of in situ-derived nitrosoalkenes leading to chiral nonracemic α-sulfenylated ketones is described. The transformation proceeds in an umpolung fashion, relative to enolate/azaenolate methods, and uses simple thiols, thereby obviating the need for elecrophilic sulfur reagents. Moreover, excellent ee's were obtained starting from a variety of α-chloro oximes, including cyclic and acyclyic systems. Chiral nonracemic sulfur containing compounds are important both biologically, and in synthetic context through their use as chiral auxiliaries, ligands for metal catalysis, and organocatalysts. Also, herein, the addition of cuprates to α,β-epoxy tosylhydrazones is described. The transformation is operationally simple and efficient and has the unusual feature of giving high syn selectivity, which is opposite of that produced by a simple SN2-type epoxide opening reaction. This method compatible with α,β-epoxy tosylhydrazones with additional α-substitution, which provides access to aldol-like products that would be impossible to make using traditional enolate chemistry. Moreover, this method is compatible with a wide variety of both cyclic and acyclic α,β-epoxy tosylhydrazones, and produces dr's of >20:1.
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Martin, Steven Jay. "Alkene umpolung initiated by dimethyl(methylthio)sulfonium fluoroborate carbon and oxygen nucleophiles /." 1985. http://catalog.hathitrust.org/api/volumes/oclc/13097974.html.
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Thesis (Ph. D.)--University of Wisconsin--Madison, 1985.Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 234-250).
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McFarlane, Michael Thomas. "Metal-catalyzed cross-coupling reactions with dithiolanes and dithianes." 2012. http://hdl.handle.net/1993/13706.
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Creating new carbon-carbon bonds is one of the most important and challenging reactions in organic synthesis. Metal-catalyzed cross-coupling reactions have emerged as one of the preferred methods of producing new carbon-carbon bonds, and this work led to the 2010 Nobel Prize in Chemistry.
This thesis was aimed at expanding the current research in the area of metal-catalyzed cross-coupling reactions to include new applications with dithiolane and dithiane protecting groups. 1,3-Dithiolane and 1,3-dithiane derivatives are particularly interesting molecules in that they can be deprotonated by a strong base to form anions, which can then be used for carbon-carbon bond synthesis. This thesis describes the investigation into the use of dithiolanes and dithianes in metal-catalyzed cross-coupling reactions, as well as some of the challenges faced in performing this sulfur-based chemistry.
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Pfrommer, Sarah [Verfasser]. "Die Umpolung regenerierbarer retinaler Ganglienzellen in ein fremdes Zielgebiet / vorgelegt von Sarah Pfrommer." 2010. http://d-nb.info/1010687115/34.
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"The Stetter reaction : synthesis of complex spiro Bis-indanes and studies on quaternary centre formation." Thesis, 2012. http://hdl.handle.net/10388/ETD-2012-09-523.
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This work covers recent advances in the Stetter reaction, including two novel domino Stetter reactions and preliminary studies on quaternary center formation via the intermolecular Stetter reaction.
The N-heterocyclic carbene (NHC) catalyzed domino Stetter-aldol-Michael dimerization of o-formyl chalcone derivatives 36 affords spiro bis-indane homo-dimers 38 in good yields and moderate to high diastereomeric ratios. Three carbon-carbon bonds, including the hindered quaternary center at the spiro ring junction, form at a remarkable rate under mild reaction conditions. Spiro bis-indanes 39 are also produced in moderate to good yields through the Stetter-aldol-aldol reactions of o-formyl chalcones 36 with phthalaldehyde derivatives 27. The scope, limitations, and potential applications of these remarkable complexity-generating domino reactions are discussed.
Preliminary results in the formation of quaternary centers via the intermolecular Stetter reaction are also disclosed. The viability of β,β-disubstitued Meldrum’s acid, diethyl malonate, and malononitrile alkylidenes as well as diphenylcyclopropenone and 3-phenylcyclobutenone as acceptors in the Stetter reaction are discussed.
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Alexander, Sean Geoffrey. "NHC-supported mixed halohydrides of aluminium and related studies." Thesis, 2011. http://hdl.handle.net/2440/103164.
Full textAbstract:
Chapter 1. General introduction
This chapter comprises a comprehensive overview of group 13 chemistry, including the elements
of group 13, the trihydrides of aluminium and gallium and their Lewis base adducts, and a brief
overview of aluminium and gallium trihalides and their respective Lewis base adducts.
Chapter 2. Lewis base adducts of group 13 mixed halide-hydrides
This chapter consists of an overview of the existing mixed halohydrides of aluminium and
gallium, and an introduction to carbenes, including NHCs. The synthesis and discussion of
numerous new mixed halohydrides of aluminium and gallium is presented.
Chapter 3. Selected reductions with mixed halohydride reagents
This chapter discusses the application of compounds from Chapter 2 as organic reducing agents
and comparison with literature concerning hydrometallation with trihydride congeners.
Chapter 4. Triazenide complexes of alane and gallane
This chapter includes the synthesis of several new triazene species and their precursors, and their
application as support ligands for aluminium and gallium mono- and dihydrides.
Chapter 5.
This chapter includes the synthesis of several “super-bulky” NHCs, their precursor
diazabutadienes and terphenyls, and preliminary use in coordination chemistry.Thesis (Ph.D.) -- University of Adelaide, School of Chemistry and Physics, 2011.
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Negrão, Ana Cláudia Ribeiro. "Synthesis of an Unnatural Amino Acid Based on Hypervalent Iodine Reagents: Exploring the Potential of Umpolung Reactions." Master's thesis, 2022. http://hdl.handle.net/10362/132392.
Full textAbstract:
The C-N bond is one of the most abundant bonds in organic compounds and has great relevance due to the diverse biological activities displayed by nitrogen-containing compounds. Additionally, there has been an increasing interest by the pharmaceutical industry in drugs and produgs bearing the amino acid moiety. Driven by the broad scope of their biotechnological application, unnatural amino acids have been receiving significant attention in the last decades. Thus, the search for efficient methods for the construction of C-N bonds assumes great importance and is always on demand. Efforts have been made towards the synthesis of unnatural amino acids, however there is still room for improvement, as their preparation often involves limitations such as complex and multi-step reactions and poor enantio- and stereoselectivity.
Taking advantage of the umpolung reactivity of hypervalent iodine compounds, 4 benziodoxolone-derived iodine(III) reagents containing a transferable primary amine have been developed. These novel reagents have been employed in electrophilic a-amination reactions of suitable carbon nucleophiles leading to the desired a-aminated products in up to 83% yield. In order to be used as carbon nucleophiles, indanone-derived-b-keto esters bearing different electron-donating and electron-withdrawing ring-substituents were synthesized. Structural confirmation of the obtained products was based on NMR and IR spectroscopy and mass spectrometry.
Furthermore, it was envisioned that this umpolung strategy for a-amination using hypervalent iodine reagents could serve as a promising approach towards the synthesis of unnatural a-amino acids. Thus, one a-aminated product was chosen as model substrate for proof of concept. This product was submitted to a catalytic hydrogenolysis protocol and the resulting amino ester was hydrolysed giving access to the first unnatural amino acid prepared in an umpolung strategy using hypervalent iodine reagents.A ligação C-N, uma das ligações mais comuns em compostos orgânicos, possui grande relevância devido às variadas atividades biológicas demonstradas por compostos que contém azoto. Além disto, tem havido um interesse crescente por parte da indústria farmacêutica em fármacos e pró-fármacos que possuam a unidade aminoácido. Nas últimas décadas, os aminoácidos não naturais têm recebido uma atenção significativa motivada pelo leque imenso de aplicações biotecnológicas que estes possuem. Desta forma, a procura por métodos mais eficientes para a construção de ligações C-N assume uma grande dimensão e encontra-se em constante demanda. Esforços têm sido prosseguidos no sentido de sintetizar aminoácidos não naturais. No entanto, ainda existe margem para progresso uma vez que a sua preparação envolve algumas limitações tais como passos reacionais múltiplos e complexos e falta de enantio- e estereosseletividade. Tirando partido da reatividade tipo umpolung dos reagentes de iodo hipervalente, foram desenvolvidos 4 reagentes de iodo(III) derivados da benziodoxolona possuindo uma amina primária transferível. Estes novos reagentes foram aplicados em reações de a-aminação de nucleófilos de carbono adequados, permitindo aceder aos produtos a-aminados correspondentes com rendimentos até 83%. A fim de serem utilizados como nucleófilos de carbono foram, também, preparados b-ceto esteres derivados da indanona com diferentes substituintes no anel aromático - eletrodoadores e eletroatratores. A confirmação estrutural dos produtos obtidos foi realizada com recurso às espetroscopias de RMN e IV e espetrometria de massa. Perspetivou-se que esta estratégia tipo umpolung para a-aminação utilizando, para tal, reagentes de iodo hipervalente pudesse ser aplicada à síntese de aminoácidos não naturais. Assim, um produto a-aminado obtido no decorrer deste projeto foi utilizado como substrato modelo para prova de conceito. Este produto foi submetido a um protocolo de hidrogenólise catalítica e, o amino éster resultante foi hidrolisado tendo permitido, desta maneira, aceder ao primeiro aminoácido não natural preparado através de uma estratégia tipo umpolung utilizando reagentes de iodo hipervalente.
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Madenci, Süreyya [Verfasser]. "Substitution von molekularen Klammern an den Naphtalin-Seitenwänden : chirale Derivate; Versuche zur Umpolung der Rezeptoreigenschaften / vorgelegt von Süreyya Madenci." 2008. http://d-nb.info/990190196/34.
Full text
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Sharma, Maya. "Synthesis of a fluorous benzodithiol support and its utility in the construction of diverse ring systems." 2008. http://hdl.handle.net/1993/3063.
Full textAbstract:
A method for the synthesis of a symmetrical fluorous tagged benzodithiol support has been developed through a seven-step synthetic pathway. The Wittig olefination and catalytic hydrogenation reactions were employed to attach two perfluoroalkyl chains in the o-positions of phthalaldehyde. These fluorous tags were used as soluble supports which facilitated the purification of the crude reaction mixtures using fluorous solid phase extraction (FSPE).
A selective and high yielding dibromination reaction was developed to synthesize a fluorous tagged 1,2-dibromo aryl compound. A thorough study was carried out to demonstrate the ease of an aryl-sulfur bond formation with the 1,2-dibromo compound varying palladium catalysts and ligands. A new palladium catalyzed dithiolation reaction is reported to synthesize a surrogated dithiol, which was exploited as a precursor for the synthesis of hitherto inaccessible symmetrical fluorous tagged benzodithiol support. The utility of the benzodithiol was explored by the synthesis of benzodithianes with two aldehydes. The lithiated dithiane generated was further used to form a C-C bond employing the umpolung reaction. The ring-closing metathesis reaction using Grubbs II catalyst was performed to construct 5-membered and 6-membered spiro-ring systems. Several approaches were made to form a C-C bond with lithiated dithianes using various nitrogen containing electrophiles leading to N-heterocycles.October 2008
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Desjardins, Samuel. "Polycyclisation oxydative et son application en synthèse asymétrique." Mémoire, 2013. http://www.archipel.uqam.ca/5812/1/M12777.pdf.
Full textAbstract:
L'activation par voie oxydative de dérivés phénoliques contenant une chaine latérale insaturée avec un réactif d'iode hypervalent permet la formation de produits bicycliques et tricycliques via l'intermédiaire d'un processus de cyclisation cationique en cascade. Il s'agit d'un procédé efficace permettant, en une seule étape de synthèse, de construire le squelette principal de plusieurs produits naturels avec un stéréocontrôle total, régi par les interactions de contrainte 1,3 allyliques et par la configuration des doubles liaisons des chaînes latérales. Une application de cette nouvelle méthodologie pour la synthèse du squelette de la famille des kauranes a été réalisée énantiosélectivement, en une seule étape, via la déaromatisation d'un phénol élaboré. De plus, une version oxydative de la réaction de Polonovski classique permet avec l'aide d'un iode hypervalent, de transformer une amine benzylique en aldéhyde chimiosélectivement.
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MOTS-CLÉS DE L’AUTEUR : Déaromatisation, Iode hypervalent, Phénol, Prins, Polonovski, Produit naturel, Polycyclisation, Umpolung