Over the last two centuries, the discovery and application of catalysts has had a substantial impact on how and what chemicals are produced.Given their broad significance, our group has focused on developing new catalyst systems that are recoverable and reusable, in an attempt to reduce concomitant costs. Our efforts have centered on constructing a recyclable chiral heterogeneous catalyst capable of effecting asymmetric hydrogenations of olefins with high stereoselectivity. A class of phosphinoimidazoline ligands, developed by researchers at Boehringer-Ingelheim, known as BIPI ligands, have proven efficacious in the asymmetric reduction of alkenes. However, these chiral ligands are homogeneous and coordinated to precious metals, rendering them irrecoverable and expensive. To address these issues, our group has derivatized the BIPI ligand-metal complex and immobilized it to the surface of graphene oxide as well as polystyrene. Their efficacy and recyclability toward the asymmetric hydrogenation of a functionalized olefin have been evaluated. Another facet of our work has included developing a cost effective synthetic process to artemisinin, the gold standard drug in the treatment of malaria.As a natural product, artemisinin’s worldwide supply remains highly unpredictable, contributing to great price volatility.Combining the benefits of catalysis and the advantages of continuous flow chemistry, our research has sought to develop an economical approach to convert a biosynthetic precursor, artemisinic acid, to artemisinin in three chemical transformations. High-throughput experimentation allowed us to screen a prodigious number of catalysts and identify those effective in the asymmetric hydrogenation artemisinic acid to dihydroartemisinic acid, the first step in the transformation. This screening directed us to an inexpensive, heterogeneous ruthenium catalyst. The second step of the process includes the photooxygenation of dihydroartemisinic acid, which involves photochemically generated singlet oxygen. We have evaluated a commercially available heterogeneous photocatalyst packed in a transparent bed, surrounded by light emitting diodes in the continuous photooxygenation of dihydroartemisinic acid to dihydroartemisinic acid hydroperoxide. The third and final step, an acid induced hock cleavage, initiates an intricate cascading reaction that installs an endoperoxide bridge to deliver artemisinin. Our process afforded a 57% yield from dihydroartemisinic acid to artemisinin.

La photochimie est devenue une méthode utile et efficace en synthèse organique. La complémentarité avec la chimie traditionnelle thermique en fait une alternative de choix, en plus de pouvoir accéder à des réactivités inopérantes à d’autres régimes. La première partie de cette thèse présente l’élaboration d’un montage photochimique pour la chimie en débit continu et des méthodes photochimiques pour la synthèse de carbazoles par photocyclisation 6π de triaryles amines. La comparaison entre deux méthodes photochimiques, l’une visible, l’autre UV sera aussi examiné à la première partie. L’irradiation UV donne de meilleurs rendements en général, mais n’admet pas certains groupes fonctionnels qui sont toléré sous la lumière visible. De plus une certaine complémentarité est observée entre les deux méthodes. La deuxième partie explore le développement d’un photocatalyseur au cuivre(I) pour la synthèse de 1,2-diols par une étape de PCET. Un photocatalyseur compétent pour la dimérisation d’aldéhydes et de cétones activées par une étape de PCET a ainsi pu être synthétisé. Ce photocatalyseur est issu de l’étude d’une librairie de complexes de cuivre(I) qui a permis de déterminer quels ligands seraient en mesure de catalyser une étape de PCET. En somme, une exploration de la photocyclisation de triaryles amines a permis de solidifier les connaissances sur leur comportement de cyclisation et la synthèse d’un nouveau catalyseur bifonctionnel permettant des PCET promet des avancés dans l’activation homolytique de carbonyles. / Photochemistry and photocatalysis have had a significant impact in organic synthesis, often offering low-energy alternatives to traditional thermal chemistry, or even affording complementary reactivity. The thesis is divided into two sections describing photochemical methods for the synthesis of carbazoles and 1,2-diols. The first section described the conception of a flow chemistry apparatus and a comparison of two photochemical methods, one using visible light and another using UV-light for carbazole synthesis via flow chemistry. While UV irradiation affords better yields, it does not tolerate sensitive functionals groups that are accessible when irradiated in the visible range. The chemoselectivity of the carbazoles synthesis is also examined with both methods. The second section explores the development of copper(I) photocatalysts for promoting a reductive proton-coupled electron transfer (PCET). General guidelines and structure/activity relationships were established for the PCET process through evaluation of a 50-member library of heteroleptic copper complexes bearing one diamine and one bisphosphine. Furthermore, it was demonstrated that a copper photocatalyst could be designed a priori to incorporate a hydrogen-bond donor within its framework to promote PCET reactions. The newly designed catalyst was applied in a photochemical pinacol coupling and was capable of transforming substrates that were unreactive using existing technology, even with a hydrogen bond donor that was orders of magnitude less acidic than common additives. Mechanistic studies demonstrated that the copper catalyst functioned via reductive quenching before PCET, which could not have been easily predicted given the literature precedent. The thesis describes the preparation of molecules such as pinacols and heterocycles that are of high value. Importantly, the new photochemical methods developed lower the energy requirements for synthesis, decrease reaction times and use continuous flow technology that would facilitate and intensify scale-up. In sum, the research herein contributes to efforts to promote sustainable and greener methods of synthesis for fine chemicals.

<p>Total synthesis of massarinolin A, purpurlides B, D, E, 2,3-deoxypurpurolide C, phleghenrines A and B were finished. A halogen bond promoted michael addiation was discovered during mechanism study toward diamination of allenes. Computational chemsitry study conducted toward the selectivity of 2+2 reaction supported the proposed key reaction during total synthesis of gibberellic acid 18.</p>

Les macrocycles peptidiques sont des molécules ayant une importance pharmaceutique grandissante. Le cycle restreint le nombre de conformations accessibles et peut potentiellement améliorer un certain nombre de paramètres pharmacocinétiques et pharmacodynamiques, en comparaison avec un analogue linéaire. La synthèse de macrocycles exige de favoriser la réaction intramoléculaire par rapport à la réaction intermoléculaire, ce qui est souvent réalisé par dilution du milieu dans l’ordre du mM. Les contraintes de concentration rendent certaines réactions de macrocyclisation peu pratiques. Par exemple, les processus photochimiques sont intrinsèquement sensibles à la concentration et à la pénétration de la lumière. Leur efficacité peut être améliorée en réduisant la longueur du trajet optique de la lumière dans une solution, mais cette solution est difficilement transposable aux procédés de macrocyclisation. Le chapitre 1 de ce mémoire introduit les concepts de macrocyclisation et de réaction photochimique. Le chapitre 2 introduit, d’une part, les réactions de macrocyclisation photochimique et, d’une autre, le travail de conception réalisé par Émilie Morin d’un réacteur hybride en flux continu favorisant ce type de réaction. Le chapitre 3 explicite les démarches effectuées pour réaliser les objectifs de ce mémoire. Plus précisément, l’oxydation aérobique photocatalytique de thiols en disulfure dans le réacteur hybride permet l’isolation de cinq macrocycles avec de meilleurs rendements qu’en montage en batch. Le couplage de Glaser-Hay est utilisé pour dériver un des macrocycles synthétisés dans le réacteur hybride. Enfin, l’investigation préliminaire de deux autres systèmes photocatalytique/photochimique est abordée pour leur application future dans le réacteur nouvellement développé. / Peptide macrocycles are molecules of increasing pharmaceutical importance. Their restricted conformations can potentially improve a number of pharmacokinetic and pharmacodynamic parameters, compared to their linear analogs. The synthesis of macrocycles requires favoring the intramolecular reaction over the intermolecular reaction, which is often achieved by dilution in the order of mM. The constraints of concentration make certain macrocyclization reactions unpractical. For example, photochemical processes are inherently sensitive to concentration and light penetration. Their efficiency can be improved by reducing the length of the optical path of the light in a solution, but the solution is difficult to transfer to macrocyclization processes. Chapter 1 of the thesis introduces the concepts of macrocyclization and photochemical reactions. Chapter 2 introduces photochemical macrocyclization reactions and the design work carried out by Émilie Morin of a continuous flow hybrid reactor. Chapter 3 explains the steps taken to achieve the objectives of the thesis. More specifically, the photocatalytic aerobic oxidation of thiols to disulfide in the hybrid reactor allows the isolation of five macrocycles with better yields than in batch. The Glaser-Hay coupling is used to derivatize one of the macrocycles synthesized in the hybrid reactor. Finally, the preliminary investigation of two other photocatalytic/photochemical systems is discussed for their future application in the newly developed reactor.

No description available.

La réaction de macrocyclisation par métathèse est une réaction clé en synthèse organique et qui comporte de nombreux défis. Les méthodes traditionnelles de macrocyclisation impliquent par exemple la haute dilution du mélange réactionnel et l’emploie d’une pompe seringue. Dans cette thèse de doctorat, une méthode qui évite l’emploi des techniques de haute dilution a été développée. Cette méthode a été appliquée à la synthèse de cyclophanes macrocycliques. De plus, la synthèse totale de la néomarchantine A, un macrocycle bisbibenzylique, a été réalisée en 12 étapes à partir de produits commercialement disponibles avec un couplage d’Ullmann, un couplage de Wittig et une macrocyclisation par métathèse comme réactions clés. La chimie en débit continu, une méthode facilement applicable en milieu industriel, a été explorée. Cette technologie a été appliquée à l’étape clé de macrocyclisation par métathèse pour la synthèse de la néomarchantine A ainsi que pour la synthèse d’un musc macrocyclique breveté par la compagnie « International Flavors and Fragrances (IFF) ». / The macrocyclic metathesis reaction is a key reaction in organic synthesis and possesses numerous challenges. Traditional methods typically involve high dilution conditions and the use of a syringe pump. In this doctoral thesis, a method that avoids the use of dilution technics has been developed. This method has been applied to the synthesis of macrocyclic cyclophanes. Furthermore, total synthesis of neomarchantin A, a bisbibenzyl macrocycle, has been done in 12 steps from commercially available reagents with an Ullmann coupling, a Wittig coupling and a macrocyclic metathesis reaction as key steps. Continuous flow chemistry, a method easily applicable in an industrial setting, has been explored. This technology was applied to the key macrocyclization step of the neomarchantin A and for the synthesis of a macrocyclic musk patented by International Flavors and Fragrances (IFF).

Polymer foams belong to the solid foams family which are versatile materials, extensively used for a large number of applications such as automotive, packaging, sport products, thermal and acoustic insulators, tissue engineering or liquid absorbents. Composed of air bubbles entrapped in a continuous solid network, they combine the properties of the polymer with those of the foam to create an intriguing and complex material. Incorporating a foam into a polymer network not only allows one to use the wide range of interesting properties that the polymer offers, but also permits to profit from the advantageous properties of foam including lightness, low density, compressibility and high surface-to-volume ratio. Generally, the properties of polymer foams are strongly related to their density and their structure (bubble size and size distribution, bubble arrangement, open vs closed cells). Having a good control over foam properties is thus achieved by first controlling its density and structure.We developed a technique in which solid foams are generated essentially in a two-step process: a sufficiently stable liquid foam with well-controlled structural properties is generated in a first step, and then solidified in a second one. With such a two-step approach, the generation of solid foams can be divided into a number of well-separated sub-tasks which can be controlled and optimised separately. The transition from liquid to solid state is a sensitive issue of a great importance and therefore needs to be controlled with sufficient accuracy. It is essentially composed of three key steps: foam generation, mixing of reactants and foam solidification and requires the optimisation of foam stability in conjunction with an appropriate choice of both foaming time and solidification time. Furthermore, a good homogeneity of the polymer foam calls for a good mixing of the different reactants involved in the foaming and the polymerisation.A particularly powerful demonstration of the advantages of this approach is given by solidifying monodisperse liquid foams generated using millifluidic technique, in which all bubbles have the same size. In a liquid foam, equal-volume bubbles self-order into periodic, close-packed structures under gravity or confinement. As such, monodisperse foams provide simultaneous control over the size and the organisation of the pores in the final solid with an accuracy which is expected to give rise to a better understanding of the structure-property relationship of porous solids and to the development of new porous materials.We therefore aim to explore the new spectrum of properties, which polymer foams offer when we introduce an ordered structure into them since the most widely used polymer foams nowadays have disordered structures. The goal of our study is to demonstrate the feasibility of this two-step approach for different classes of polymers, including biomolecular hydrogel, superabsorbent polymer and polyurethane.For the generation of the structured polymer foams we use Lab-on-a-Chip technologies which allow the "shrinking" of large-scale set-ups to micro/millimetic scale. It permits also to perform "flow chemistry" in which the various liquid and gaseous ingredients of the foam are injected and mixed in a purpose-designed network of the micro- and millifluidic Lab-on-a-Chip. We adjust this approach according to the requirements of each polymer system, i.e. the foaming and the mixing techniques are chosen to fit the properties of each system, and can be exchanged to fit the properties of the studied systems.

Myo-inositol is ubiquitous in nature and is found at the structural core of a diverse range of biologically important derivatives, including phosphatidylinositols, inositol phosphates and mycothiol. The synthesis of myo-inositol derivatives is notoriously difficult due to the need to control both regio- and enantioselectivity. As a result, synthetic routes to derivatives of this type are often lengthy and low yielding. The first biosynthetic step in the production of all myo-inositol metabolites is the isomerisation of D-glucose 6- phosphate to L-myo-inositol 1-phosphate as mediated by L-myo-inositol 1-phosphate synthase (INO1). For the protozoan parasite Trypanosoma brucei, INO1 is essential for survival and its version of the enzyme (TbINO1) has a high turnover. This makes TbINO1 an attractive candidate for the biocatalytic production of L-myo-inositol 1- phosphate, and a potential starting point for drastically shortened syntheses of important myo-inositol derivatives. The production of L-myo-inositol 1-phosphate by TbINO1 has been optimised to achieve complete conversion in reaction conditions that facilitate product isolation. Due to problems with an in-batch process, the TbINO1 enzyme was immobilised and the process was transferred to a flow system. This has allowed for production of significant quantities of L-myo-inositol 1-phosphate with a high level of purity. L-myo-inositol 1- phosphate obtained from the flow system has been used to prepare mycothiol glycosylation acceptor, 1,2,4,5,6-penta-O-acetyl-D-myo-inositol, in a concise synthesis with a greatly improved yield over the literature.

Les protéoglycanes sont des macromolécules composées de glycosaminoglycanes (GAGs), liés de manière covalente à une protéine porteuse. Les GAGs sont impliqués dans de nombreux processus biologiques, comme la croissance et la prolifération des cellules, et également dans de nombreuses pathologies, incluant l’arthrose, la maladie d’Alzheimer et des cancers. Leur biosynthèse fait intervenir des O-glycosyltransférases et commence par la formation de la zone de liaison tétrasaccharidique. Celle-ci initie la formation de deux types de chaînes de GAGs, les héparines / sulfates d’héparine avec l’action de l’EXTL3 et les sulfates de chondroïtines ou de dermatanes avec l’action de la CSGalNAcT-1. Dans cette biosynthèse, la zone de liaison peut être sulfatée mais le rôle de ces sulfatations est encore peu connu.L’objectif de ce travail était de synthétiser des disaccharides de la zone de liaison ainsi que les trisaccharides de transfert, avec le premier sucre aminé des chaînes de GAGs, diversement monosulfatés ou non, dans le but de comprendre le rôle de ces sulfatations sur les enzymes de bifurcation.Différentes méthodes d’activation, micro-ondes et chimie en flux continu, ont également été testées pour sulfater des mono-, di- et trisaccharides. / Proteoglycans are macromolecules composed of glycosaminoglycans chains (GAGs) covalently linked to a core protein. GAGs are implicated in many biological processes, such as cells growth and proliferation, and they are also involved in several diseases including osteoarthritis, Alzheimer’s disease and cancers. Their biosynthesis involves the action of O-glycosyltransferases and starts with the formation of a tetrasaccharidic linkage region. This GAGs linkage region initiates the formation of two types of GAGs chains, heparin/heparan sulfates with the action of EXTL3 and chondroitin sulfates/dermatan sulfates with the action of CSGalNAcT-1. In this biosynthesis, the linkage region may be sulfated, but the role of these sulfations is still poorly understood.The objective of this work was to synthetize disaccharides of the linkage region and transfer trisaccharides, with the first aminosugar of the GAGs chains, variously monosulfated or not, in order to study the role of sulfations on the bifurcation enzymes.Different activation methods, microwaves and flow chemistry, were also tested to sulfate mono-, di- and trisaccharides.

[pt] Materiais nanoestruturados como nanocristais semicondutores de telureto de cádmio (QDs de CdTe) e nanopartículas metálicas de prata (NPsAg) têm sido utilizados como nanosondas analíticas, explorando suas propriedades de luminescência e de ressonância de superfície plasmônica localizada (LSPR), respectivamente, sejam em dispersão coloidal ou em filmes finos. Em função das suas configurações experimentais, sistemas microfluídicos podem ser utilizados tanto para síntese de materiais nanoestruturados quanto para análise de analitos de interesses biológicos. No presente estudo, QDs-CdTe encapados com ácido tioglicólico (TGA) foram sintetizados em batelada e em regime de fluxo contínuo a partir da injeção dos precursores de cádmio e telúrio por bombas-seringas para um sistema de tubos de aço passando por fornos tubulares horizontais com controladores de temperatura (110-140 graus Celsius). Para otimizar os parâmetros experimentais foram variados a taxa de vazão volumétrica (0,15 - 0,03 mL min(-1)) e a razão molar de Cd:Te (1:0,3 - 1:1,5). Os resultados demonstraram que o efeito da razão molar na síntese de QDs apresentou ser mais significativo em comparação à variação da temperatura, obtendo QDs com FWHM de 64 – 86 nm. Filmes luminescentes poliméricos de PVA e PDMS foram desenvolvidos pelas técnicas de impregnação, mistura de QDs na matriz polimérica e por spin coating. Pela técnica de spin coating foram produzidos filmes de 58,7 nm. Filmes de QDs sobre substrato de vidro foram obtidos pelo processo de silanização da superfície do vidro. Todos os filmes apresentaram instabilidade de luminescência ao longo do tempo. Dispersões coloidais de NPsAg revestidas com ligantes orgânicos citrato e tartarato, nas razões Ag+:ligante (1:1 e 1:0,5), foram sintetizadas a partir da injeção dos ligantes e nitrato de prata por bombas-seringas em um microrreator tubular polimérico. As NPsAg-citrato e NPsAg-tartarato apresentaram cargas superficiais negativas e tamanhos médios de 12,5 nm. As bandas LSPR foram observadas para monitorar a interação entre as nanosonda de prata e os fármacos aminoglicosidico em fluxo contínuo mediante um fotômetro acoplado a uma cela de fluxo. Nas concentrações iguais ou maior que 2 × 10(-7) mol L(-1), produziu uma mudança no perfil espectral da nanosonda de NPsAg, com o decaimento do sinal no comprimento de onda 404 nm e o surgimento de uma nova banda em 480 nm, resultante da aglomeração das nanopartículas. Além disso, as NPsAg-tartarato foram depositadas sobre substrato de vidro para realização de filmes fino com objetivo de desenvolver, em parceria com a Universidade Federal de Pernambuco (UFPE), um biosensor baseado na ressonância plasmônica localizada (LSPR) para determinação do antígeno Candida albicans. / [en] Nanostructured materials such as cadmium telluride semiconductor nanocrystals (QDs-CdTe) and silver nanoparticles (NPsAg) have been used as analytical nanoprobes, exploiting their luminescence properties and localized plasmonic surface resonance (LSPR), respectively, both in colloidal suspension or on thin solid films. Due to their experimental set-up, microfluidic systems can be used, both, for synthesis of nanostructured materials and for the analytic detection of biological and pharmaceutical compounds. In the present study, thioglycolic acid (TGA) coated QDs-CdTe were synthesized in batch and in a continuous flow regime from the injection of cadmium and tellurium precursors by syringe pumps into a steel tubes through horizontal tubular furnaces with temperature controllers (110 - 140 Celsius degrees). To optimize the experimental conditions, we modulate the volumetric flow rate (0.15 - 0.03 mL min(-1)) and the Cd:Te molar ratio (1:0.3 - 1:1.5). The results showed that the effect of the molar ratio on the synthesis of QDs was more significant compared to the temperature variation, obtaining QDs with FWHM of 64 - 86 nm. Polimeric luminescent films with PDMS e PVA were developed with impregnation, mixing QDs-TGA in PDMS and PVA and spin coating techniques. By the spin coating technique we produced luminescent film of 58.7 nm thickness. QDs-TGA film on glass substrate were obtained by means of surface silanization.All the film showed luminescence instability over time. Colloidal dispersions of NPsAg coated with the organic citrate and tartrate ligands in the Ag+/ligand ratios (1:1 and 1:0.5) were synthesized from the injection of organic ligands and silver nitrate by syringe pumps into a polymeric tubular micro-reactor. NPsAg-citrate and NPsAg-tartrate presented negative surface charges and average sizes of 12.5. The SPR band was monitored to follow the interation between the silver nanoprobe with kanamycin and neomycin drugs by means of a flow cell coupled to a photometry. At concentrations equal or greater than 2 × 10(-7) mol L(-1) the LSPR band changed its spectral profile. LSPR maximum band, centered at 404 nm, decaied and appeared a new band at 480 nm resulting from the agglomeration of the nanoparticles. Moreover, in a partnership with the Federal University of Pernambuco (UFPE), NPsAg-tartarate were deposited on glass for the realization of thin film with the object to development a biosensor based on localized plasmon resonance (LSPR) for determination of Candida albicans antigen.