A detailed mechanistic investigation of the previously reported ruthenium pseudo-dipeptide-catalyzed asymmetric transfer hydrogenation (ATH) of aromatic ketones was performed. It was found that the addition of alkali metals has a large influence on both the reaction rate and the selectivity, and that the rate of the reaction was substantially increased when THF was used as a co-solvent. A novel bimetallic mechanism for the ruthenium pseudo-dipeptide-catalyzed asymmetric reduction of prochiral ketones was proposed. There is a demand for a larger substrate scope in the ATH reaction, and heteroaromatic ketones are traditionally more challenging substrates. Normally a catalyst is developed for one benchmark substrate, and a substrate screen is carried out with the best performing catalyst. There is a high probability that for different substrates, another catalyst could outperform the one used. To circumvent this issue, a multiple screen was executed, employing a variety of ligands from different families within our group’s ligand library, and different heteroaromatic ketones to fine-tune and to find the optimum catalyst depending on the substrate. The acquired information was used in the formal total syntheses of (R)-fluoxetine and (S)-duloxetine, where the key reduction step was performed with high enantioselectivities and high yield, in each case. Furthermore, a new iron-N-heterocyclic carbene (NHC)-catalyzed hydrosilylation (HS) protocol was developed. An active catalyst was formed in situ from readily available imidazolium salts together with an iron source, and the inexpensive and benign polymethylhydrosiloxane (PMHS) was used as hydride donor. A set of sterically less demanding, potentially bidentate NHC precursors was prepared. The effect proved to be remarkable, and an unprecedented activity was observed when combining them with iron. The same system was also explored in the reduction of amides to amines with satisfactory results. / <p>At the time of doctoral defense, the following paper was unpublished and had a status as follows: Paper 2: Manuscript.</p>

Chemists have always been fascinated by the cumulated diene system of allenes with its extraordinary properties such as the axial chirality of the elongated tetrahedron and a higher reactivity than non-cumulated C-C double bonds. The equilibrium geometry for an allene is linear with orthogonal pairs of substituents. An allene incorporated into a carbocyclic ring of nine or more carbon atoms is relatively unstrained. However, if the ring size is decreased, the linear perpendicular allene will be twisted and bent until, at some point, the energy gained by pi bonding in the two double bonds will be insufficient to offset the increased strain. Furthermore, ring constraints will exert torsion toward a planar arrangement of ligands. Therefore, one of the fundemantal questions is the influence of ring size on the barrier to pi bond rotation. Herein we wish to unveil a review of our research related to desperately seeking for five membered ring allenes such as, cyclopenta-1,2-diene (1) and some of its derivatives, e.g. 2, and 3. Furthermore, we will address a simple, mild and efficient method for the reduction of 1,4-benzoquinones 4 to corresponding hydroquinones 5.

Techn. Universiẗat, Diss., 2002--Berlin.

This thesis describes selected reactivity studies of the N-heterocyclic carbene, IPr, towards a range of main group compounds. The synthesis and characterisation of sixty-three compounds, all of which incorporate IPr as a ligand in one of three coordination modes, are detailed herein. The deprotonation of IPr allowed for the isolation of an anionic source of the aIPr: ligand which was synthesised as a novel potassium salt and along with the previously reported lithium salt, was employed in reactions with group 12 and 14 bis(trimethylsilyl)amides and tetrahalides. The further chemistry of such novel products was investigated towards both electrophilic and nucleophilic reagents making use of both the pendant nucleophilic carbene functionality and the electrophilic main group centre. An alternative route to such species was investigated by the spontaneous isomerisation of IPr in the coordination sphere of group 14 tetrabromides and group 15 tribromides. The scope of this reactivity was subsequently investigated and was found to provide a simpler route to access the abnormal coordination mode of IPr. The aIPr ligand which is generated may be deprotonated by additional IPr thereby affording aIPr: ligands. The addition of halide abstracting agents allowed for the synthesis of cationic species stabilised by the coordination of either IPr or aIPr ligands. A unique, spontaneous reductive coupling of two phosphorus centres was discovered to take place upon heating a THF solution of (IPr)PBr₃. This allowed for the isolation of a bromide bridged P–P bond with reduced phosphorus centres. This facile reduction chemistry was further explored by reaction with mild reducing agents which provide access to low oxidation state phosphorus compounds in high yields. This chemistry was found to be possible (and more effective) due to the presence of the weaker phosphorus bond to bromine relative to the commonly employed chlorine ligands.

Ces dernières années, les analogues nucléosidiques ont eu un rôle majeur dans le traitement de maladies virales infectieuses tels le SIDA, les hépatites, l’herpès, la variole ou la grippe. Cependant, l’apparition de nouveaux virus ou de mutations virales ont renforcé la nécessité de développer des antiviraux plus efficaces et plus résistants. L’intensive recherche de dérivés nucléosidiques cliniquement actifs a permis l’émergence d’une multitude de nouvelles approches pour leurs synthèses. Parmi ce panel, les réactions catalysées par des métaux de transition tardifs font certainement partie des méthodes les plus importantes pour accéder à une large gamme de pharmacomodulations. Lors de ce projet de recherche, nous nous sommes intéressés à la conception, la synthèse et la découverte de nouveaux dérivés nucléosidiques en tant qu’antiviraux contre le virus de la variole. Pour ce faire, nous avons ciblé des 1,2,3-triazolo-carbanucléosides en série racémique ou énantiosélective ainsi que des nucléosides phosphonates acycliques. Dans un effort de développement et/ou d’amélioration de leurs méthodes de synthèse, nous avons également étudié la contribution de complexes au ruthénium et au cuivre contenant un carbène Nhétérocyclique (CNH) dans des réactions de métathèse croisée et de cycloaddition 1,3-dipolaire de Huisgen. Enfin, en vue d’obtenir des outils efficaces utilisables en synthèse nucléosidique, nous avons développés des nouveaux complexes au palladium portant un ligand CNH et testé leurs réactivités dans des réactions de Narylation de Buchwald-Hartwig et d’hydrogénation d’oléfines. / In the last decades, nucleoside analogues have played a major role in the treatment of viral infectious diseases, such as AIDS, hepatitis, herpes, smallpox or influenza. Nevertheless, the apparition of new or mutated viruses highlights the need of more potent and resistant antiviral therapeutics. The intense search for clinically useful nucleoside derivatives has resulted in a wealth of new approaches for their synthesis. Among them, latetransition metal-catalyzed reactions are certainly the most important methods to access variety of appealing pharmacomodulations. In this research project, we were interested in the conception, the synthesis and the discovery of new nucleoside derivatives as antiviral agents against smallpox viruses. Hence, we have targeted racemic or enantiomerically pure 1,2,3-triazolo-carbanucleosides as well as acyclic nucleoside phosphonates. In our effort into the development or/and the improvement of their synthetic methodologies, we have also studied the contribution of ruthenium and copper complexes bearing N-heterocyclic carbene (NHC) ligands in cross-metathesis and Huisgen 1,3-dipolar cycloaddition reactions. Finally, in order to obtain efficient tools useful in nucleoside synthesis, we have developed new NHC-containing palladium complexes and examined their reactivity in Buchwald-Hartwig N-arylation and olefins hydrogenation reactions.

Ce travail de thèse est consacré à la synthèse de porphyrines fusionnées à des cycles imidazolium et à l’utilisation de ces derniers comme précurseurs de ligands carbènes N-hétérocycliques (NHC). Ces composés possèdent donc deux sites de coordination, interne (le macrocycle) et externe (le ligand NHC), permettant la synthèse de complexes dinucléaires. Cette étude est principalement axée sur la synthèse de métalloporphyrines conjuguées avec des complexes d’or(I) périphériques de type [(NHC)AuCl]. En vue d’application en thérapie photodynamique (PDT), la fonctionnalisation de ces complexes par des carbohydrates (mannose) a été réalisée par substitution des ligands chlorures des complexes d’or(I) périphériques. Les tests biologiques sur cultures cellulaires montrent une nette potentialisation des propriétés photodynamiques des photosensibilisateurs comportant des ligands mannoses liés à l’or(I). Suite à cette étude, la synthèse de porphyrines fusionnées à deux cycles imidazolium a été réalisée permettant pour la première fois la synthèse de complexes trinucléaires de type Au/M/Au (M = métal interne dans la porphyrine) possédant différentes géométries. Ces composés ont ouvert des perspectives intéressantes dans le but d’obtenir des photosensibilisateurs possédant deux groupements carbohydrates à leur périphérie. De plus, il a été mis en évidence que les complexes trinucléaires de type Au/Zn/Au peuvent être utilisés comme briques de construction moléculaires pour la synthèse de polymères organométalliques en vue d’applications en (photo)catalyse. / This PhD work is devoted to the synthesis of porphyrins fused to imidazolium rings and their use as precursors of N-heterocyclic carbene ligands (NHC). Therefore, these compounds possess two coordination sites, the internal (the macrocycle) and the external (the NHC ligand) ones, allowing the synthesis of dinuclear complexes. This study is mainly centered on the synthesis of metalloporphyrins conjugated with peripheral gold(I) complexes such as [(NHC)AuCl]. In view of applications in photodynamic therapy (PDT), the functionalization of these complexes by carbohydrates was achieved through the substitution of chloride ligands of peripheral gold(I) complexes. Biological tests on cell cultures show a clear potentialization of the photodynamic properties of the photosensitizers bearing mannose ligands bound to gold(I). Following this study, the synthesis of porphyrins fused to two imidazolium rings was achieved allowing for the first time the synthesis of trinuclear species such as Au/M/Au (M = inner metal in the porphyrin core) with different geometries. These compounds open interesting perspectives in view of obtaining photosensitizers having two carbohydrates at their periphery. Moreover, it was shown that trinuclear species such as Au/Zn/Au can be used as molecular building-blocks for the synthesis of organometallic polymers in view of applications in (photo)catalysis.

L'objectif de cette thèse a été de mettre au point l'introduction d'azoles en meso d'une porphyrine par couplage d'Ullmann; Divers azoles ont pu être introduit par cette méthode avec de bons rendements, par formation d'une liaison carbone-azote. il a même été possible avec certains azotes de réaliser des doubles couplages d'Ullmann, conduisant ainsi à des 5.15-diazolyle-porphyrines. De plus, ces même conditions réactionnelles ont été utilisées pour introduire un ou deux dérivés donneurs d'électrons (carbazole, phénoxazine, phénothiazine). L'introduction d'imidazole, de triazole et de benzimidazole en meso a permis, après alkylation, d'obtenir des précurseurs de carbènes N-hétérocycles (NHC). La coordination de deux équivalents de NHC sur un sel de palladium conduit à un dimère de porphyrines via coordination exocyclique. La géométrie de coordination trans-anti autour du palladium a été confirmée par l'obtention de la structure radiocristallographique de deux complexes. Les études par électrochimie de ces complexes ont révélé une communication interporphyrinique à l'état fondamental, mise en évidence par une succession de quatre vagues monoélectroniques en oxydation. / The purpose of this thesis was to functionalize the meso position of a porphyrinWith azoles using the Ullmann coupling. Various azoles were introduced with good yieldsby using this reaction, leading to the formation of a carbon-nitrogen bond. With someazoles a double Ullmann coupling was possible, resulting in the formation of 5,15-diazolyl-porphyrins. Moreover, the same conditions were used to introduce one ortwo electron-donating groups (carbazole, phenoxazine, phenothiazine). The insertionof imidazole, triazole and benzimidazole at the meso position allowed, afteralkylation, their use as N-heterocyclic carbene (NHC). Coordination of twoequivalents of NHC to a palladium salt led to a porphyrin dimer, as a bis-carbene complex. X-Ray structures revealed that the complex’s geometry was trans-anti. Electrochemistry studies of the various dimers showed interactions between the porphyrins, highlighted by four successive oxidation peaks.

Bien que les agents anticancéreux à base de platine soient bien établis en clinique, plusieurs paramètres restent à optimiser, notamment leur toxicité et les phénomènes de résistances. La combinaison platine-carbènes N-hétérocycliques (NHCs) a montré des résultats prometteurs dans la lutte antitumorale. Ainsi, afin de développer des agents anticancéreux innovants, ce travail résume les modifications structurales étudiées dans le but d’augmenter la cytotoxicité tout en réduisant les effets secondaires des complexes. Une stratégie développée ici porte sur l’introduction de pnictogènes par échange de ligand pour observer un effet synergétique. Autrement, les efforts se sont concentrés sur les complexes de NHC-platine(IV) de leur synthèse à l’étude de leur stabilité, activité anticancéreuse et mécanisme d’action. Finalement, la combinaison des NHC-Pt à des nanotransporteurs a été étudiée afin d’améliorer leur biocompatibilité et sélectivité. / Although platinum-based anticancer drugs are well established, several shortcomings have raised concerns, namely their toxicity and resistance mechanisms. Therefore, improved anticancer drugs are strongly awaited to substitute drugs currently used in clinics. Remarkably, the combination of N-Heterocyclic Carbenes (NHCs) to platinum has recently demonstrated very promising results as anticancer agents. In the aim to access novel drugs, this work emphasizes several structural modifications to improve the cytotoxicity and lower side effects. One strategy developed herein focus on the introduction of pnictogens by ligand exchange to access a synergistic effect. Otherwise, efforts mainly focused on NHC-platinum(IV) complexes from their synthesis to stability investigation and anticancer activities and mechanism of action. Finally, the combination of NHC-Pt drugs to nanodelivery devices has been investigated in order to improve both their biocompatibility and selectivity toward cancer cells.

Etant donné le rôle des sucres dans de nombreux processus physiopatholologiques importants, le développement de nouveaux outils chimiques pour la glycobiologie est primordial. Une nouvelle approche, consistant à fonctionnaliser sélectivement la liaison C-H anomérique des sucres par insertion d’un métallocarbène, a été développée, offrant ainsi un accès aux α- et β-cétopyranosides. Celle-ci est basée sur l’utilisation d’un bromoacétate ancré en position 2 du sucre, qui joue un rôle clé au sein d’une séquence réactionnelle glycosylation stéréosélective/diazotransfert/fonctionnalisation. En effet, ce bromoacétate permet de contrôler la stéréosélectivité de la réaction de glycosylation par assistance anchimérique ; puis, il permet l’installation du précurseur de carbène afin de favoriser la quaternarisation de la position anomérique. La validation de l’approche sur des méthyl-glycosides modèles a ensuite permis son application à des disaccharides. Ces études ont par ailleurs mis en évidence la tolérance de la transformation vis-à-vis de plusieurs groupements protecteurs communs en chimie des sucres. Enfin, une étude mécanistique, effectuée sur des substrats deutérés, puis complétée par des calculs DFT, a mis en évidence que l’étape de fonctionnalisation impliquait un mécanisme concerté ou dissociatif selon l’orientation équatoriale ou axiale de la liaison C-H anomérique respectivement. / Due to the major roles of carbohydrates in numerous physiopathological processes, it is essential to develop new chemical tools for glycobiology. A new approach, consisting in the selective functionalization of the anomeric C-H bond of carbohydrates by insertion of a metal-carbene, has been developed, thus offering a new access toward α- and β-ketopyranosides. This is based on the use of a key bromoacetate grafted at position 2 of the sugar, which is the corner stone of a stereoselective glycosylation/diazotransfer/functionalization sequence. Indeed, this group firstly controls the stereoselctivity of the glycosylation step by anchimeric assistance; then, it allows the convenient installation of the carbene precursor to promote quaternarization of the anomeric position. The validation of the concept on model methyl-glycosides has allowed its application on disaccharides. In addition, the sequence has shown good tolerance toward many protecting groups commonly used in carbohydrate chemistry. On the basis of mechanistic studies involving deuterium labeled substrates and DFT calculations, we have shown that this functionalization step follows a concerted or stepwise process depending on the equatorial or axial orientation of the anomeric C-H bond, respectively.

This work deals with the enantioselective synthesis of chiral cyclohexenones from substituted 4-nitroisoxazoles and α-bromo-α,β-unsaturated aldehydes using of N-heterocyclic carbenes (NHC) as organocatalysts. The work includes the preparation of commercially unavailable NHC-precursors and the synthesis of starting materials, substituted 4-nitroisoxazoles and α-bromo-α,β-unsaturated aldehydes. The second part of the work deals with the optimization of reaction conditions of the enantioselective synthesis of chiral cyclohexenones, proceeding via an azolium dienolate intermediate, and the detailed substrate scope screening.