<p>The importance of nitrogen-containing compounds in human life has drawn us to focus on the preparation of amine derivatives, combined with the limitations associated with traditional methods for the formation of C-N bonds has prompted us to develop new and efficient syntheses, of amine and ether derivatives and explore the mechanisms of the gold(I)-catalyzed reactions.</p><p>A mixture of AuCl[P(t-Bu)2o-biphenyl] (5 mol %) and AgOTf (5 mol %) served as an effective catalyst for the intermolecular hydroamination of allenes with arylamines to form N-prenylaniline and N,N-diprenylaniline derivatives. This gold(I)-catalyzed protocol was effective for the formation of arylamines at non-forcing conditions with wide substrate scope in both allene and aniline, in high yields with good regioselectivity diastereoselectivity.</p><p>The mechanism of the gold(I)-catalyzed hydroalkoxylation and hydroamination of alcohols and carbamates with allenes, catalyzed by AuIPrCl (IPr= 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidine) and AgOTf was investigated. The experimental rate laws for both reactions indicate first-order behavior in nucleophile and catalyst and zero-order behavior in catalyst. We propose an outer-sphere mechanism with turnover limiting protonolysis for the gold(I)-catalyzed hydrofunctionalization of allenes with alcohols or carbamates based on kinetic isotope effect, saturation behavior, and stereochemical analysis of hydroalkoxylation.</p><p>The mechanism of gold(I)-catalyzed hydroamination of allenes with arylamines was examined. Specifically, we explored the hydroamination of 3-methy-1,2-butadiene with aniline catalyzed by AuCl[P(t-Bu)2o-biphenyl] (5 mol %) and AgOTf (5 mol %) in dioxane at 45 °C to form N-prenylaniline and N,N-diprenylaniline. The kinetics of this reaction were determined to be first-order in aniline, allene, and catalyst. We have concluded that the mechanism for the gold(I)-catalyzed intermolecular hydroamination of allenes with arylamines involves outer-sphere attack of aniline on the gold-&#61552;-allene complex based on stereochemical analysis of the hydroamination product from the reaction of an enantiomerically enriched allene, (R)-1-phenyl-1,2-butadiene, with 3-bromoaniline.</p> / Dissertation

No description available.

Ce travail de thèse décrit la synthèse de nouveaux ligands chiraux pour des applications en catalyse asymétrique. Nous avons ainsi synthétisé différents allènes chiraux possédant des groupements phosphines et nous les avons testés sur des métaux de transition comme l'or(I). Les allènes possédant des oxydes de phosphine ont été préparés à partir de précurseurs de l'acétate propargylique correspondant avec des rendements modérés à élevés. Nous avons pu montrer que les allènes possédant un motif pyridine se coordinent efficacement avec de l'or(I), donnant deux nouveaux types de complexes d'or vinylique. Un complexe cationique vinylique avec un fragment triphénylphosphine d’or(I) permet de préparer des dérivés fonctionnalisés tels qu’un sel d'indolizinium et un iodure de vinyle. L’autre complexe contenant le groupement de chlore d’or a été utilisé comme catalyseur dans des réactions de cyclisation catalysées par de l'or. De plus, les différents allènes synthétisés ont été étudiés dans le cadre de réarrangements catalysés par l'or. Les allènes avec les groupements 3,5-methoxyphenyl et vinylallène peuvent conduire respectivement à des produits indényle et cyclopentadiényle, portant tous deux un centre stéréogène. En outre, un transfert complet de chiralité axiale en chiralité centrée a été observé sur le produit d’indényle -oxyde de phosphine à partir de l’allène optiquement pur. L’étape suivante, nous avons préparé quelques nouveaux précatalyseurs alléniques bisphosphine bimétalliques à base d’or. Ces nouveaux complexes peuvent être utilisés dans des réactions intermoléculaires et des réactions de cyclisation catalysées à l’or. Plusieurs produits carbocycliques et hétéocycliques ont été obtenus avec des rendements modérées à excellents. Ces complexes d’or chiraux peuvent être séparés par HPLC chirale préparative. Certains des excès énantiomériques obtenus dans les réactions des cycloisomérisations sont prometteurs. / This thesis has focused on the synthesis of new ligands bearing chirality for asymmetric catalysis. We first aimed to synthesize chiral allenes with phosphine moieties and use them as ligands of transition metals such as gold(I) species. Allenes bearing a phosphine oxide group were prepared from the corresponding propargylic acetate precursors in moderate to high yields. When substituted by a pyridine substituent, these substrates efficiently combined with gold(I) species to afford two types of new vinyl gold complexes. One cationic vinyl complex featuring a triphenylphosphine gold(I) moiety can be further functionalized to give an indolizinium salt and a vinyliodide derivative. The other one bearing a chlorogold(I) group can be used as a catalyst in gold-catalyzed cyclization. Moreover, other allenes have been investigated in gold(I)-catalyzed rearrangements. To our delight, the allenes featuring a 3,5-methoxyphenyl substituent and a vinylallene can produce respectively indenyl and cyclopentadienyl phosphine oxide products bearing stereogenic centers. In addition, a complete axial-to-center chirality transfer was observed on the indenylphosphine oxide product starting from the optically pure allene. In a next attempt, we have prepared some new digold-allenyl bisphosphine precatalysts. These new complexes can be used in gold-catalyzed intermolecular reactions and cyclization reactions. Several carbo- and heterocyclic products were produced in moderate to excellent yields. These chiral gold complexes could be separated by preparative chiral HPLC. Some promising enantiomeric excesses were observed in cycloisomerization reactions.

Nous avons développé trois accès synthétiques performants à des cyclopentènones fonctionnalisées en exploitant des réactivités inattendues que nous avons découvertes. Nous avons aussi effectué la première synthèse d’isostères des flavaglines substitués par un groupement formylamino ou mésylamino en position 1b et ainsi démontré l’importance de l’hydroxyl en cette position pour la cytotoxicité de ces composés. De plus, nous avons aussi contribué à l’exploration du potentiel thérapeutique des flavaglines et d’un autre ligand des prohibitines, la fluorizoline, dans le traitement des cancers et de l’inflammation chronique des intestins, ainsi que dans la prévention des effets adverses des chimiothérapies au niveau cardiaque. / We have developed three novel synthetizes of functionalized cyclopentenones based on unexpectedreactivities that we discovered.We also developed the first synthesis of flavaglines isostere substituted by a formylamino or mesylaminogroup on the position of 1b, and demonstrated the importance of a hydroxyl group on this position forcytotoxicity.Moreover, we contributed to the exploration of the therapeutic potential of flavaglines and another ligand ofprohibitins, fluorizoline, in the treatment of cancers and intestinal chronic inflammation, and also in theprevention of the cardiac adverse effects in anticancer treatments.

Le portentol est un polypropionate qui possède une structure spirocyclique très originale. Cette molécule, dont il n'existe encore aucune synthèse totale, a été isolée du lichen Rocella portentosa à la fin des années 1960. Dans le but d'accéder au squelette du portentol, nous avons développé une méthodologie visant à synthétiser des spirotétrahydropyranes fonctionnalisés via une cyclisation de Prins. Au cours de ce travail, un phénomène de dédoublement cinétique dynamique a aussi été mis en évidence. La stachybotrine C, isolée à partir de la bactérie Stachybotrys parvispora, possède des propriétés neurotrophiques et neuroprotectrices très intéressantes. Deux voies de synthèse ont été envisagées pour préparer ce produit naturel. La première voie repose sur une réaction d'hydroarylation d'un éther propargylique catalysée à l'or, suivie d'une oxydation régiosélective du chromène résultant. La seconde voie fait intervenir une étape clé d'époxydation/cyclisation d'un alkénylphénol obtenu suite à un réarrangement de Claisen. Ces travaux nous ont permis d'accomplir la synthèse totale de la stachybotrine C, de réviser sa structure et de déterminer sa configuration absolue. / Portentol is a polypropionate with an unusual spirocylic structure. This natural product, which has never been synthesized, has been isolated from the lichen Rocella portentosa. To access the spiranic moiety of the portentol, we have developed a methodology to synthesize spirotetrahydropyranes through a Prins cyclization. Through the study of the scope of this reaction, an usual dynamic kinetic resolution has been highlighted. Stachybotrin C, isolated from the bacteria Stachybotrys parvispora, exhibits interesting neuritogenic and neuroprotective properties. To prepare this natural product, two synthetic routes have been investigated. The first one is based on a gold-catalyzed hydroarylation of a propargyllic ether followed by a regioselective oxidation of the resulting chromene. The second pathway involves as a key step an epoxydation/cyclisation of a phenol prepared via a Claisen rearrangment. We accomplished the synthesis of stachybotrin C, revised its structure and established its absolute configuration.

Recently, there has been a growing interest in semiconductor and semiconducting oxide nanowires for applications in electronics, energy conversion, energy storage and optoelectronic devices such as field effect transistors, solar cells, Li- ion batteries, gas sensors, light emitting diodes, field emission displays etc. Semiconductor and semiconducting oxide nanowires have been synthesized widely by different vapor transport methods. However, conditions like high growth temperature, low vacuum, carrier gases for the growth of nanowires, limit the applicability of the processes for the growth of nanowires on a large scale for different applications. In this thesis work, studies have been made on the growth of semiconductor and semiconducting oxide nanowires at a relatively lower substrate temperature (< 500 °C), in a high vacuum (1× 10-5 mbar), without employing any carrier gas, by electron beam and resistive thermal evaporation processes. The morphology, microstructure, and composition of the nanowires have been investigated using analytical techniques such as SEM, EDX, XRD, XPS, and TEM. The optical properties of the films such as reflectance, transmittance in the UV-visible and near IR region were studied using a spectrophotometer. Germanium nanowires were grown at a relatively lower substrate temperature of 380-450 °C on Si substrates by electron beam evaporation (EBE) process using a Au-assisted Vapor-Liquid-Solid mechanism. High purity Ge was evaporated in a high vacuum of 1× 10-5 mbar, and gold catalyst coated substrates maintained at a temperature of 380-450 °C resulted in the growth of germanium nanowires via Au-catalyzed VLS growth. The influence of deposition parameters such as the growth temperature, Ge evaporation rate, growth duration, and gold catalyst layer thickness has been investigated. The structural, morphological and compositional studies have shown that the grown nanowires were single-crystalline in nature and free from impurities. The growth mechanism of Germanium nanowires by EBE has been discussed. Studies were also made on Silicon nanowire growth with Indium and Bismuth as catalysts by electron beam evaporation. For the first time, silicon nanowires were grown with alternative catalysts by the e-beam evaporation method. The use of alternative catalysts such as Indium and Bismuth results in the decrease of nanowire growth temperature compared to Au catalyzed Si nanowire growth. The doping of the silicon nanowires is possible with an alternative catalyst. The second part of the thesis concerns the growth of oxide semiconductors such as SnO2, Sn doped Indium oxide (ITO) nanowires by the electron beam evaporation method. For the first time, SnO2 nanowires were grown with a Au-assisted VLS mechanism by the electron beam evaporation method at a low substrate temperature of 450 °C. SEM, XRD, XPS, TEM, EDS studies on the grown nanowires showed that they were single crystalline in nature and free of impurities. The influence of deposition parameters such as the growth temperature, oxygen partial pressure, evaporation rate of Sn, and the growth duration has been investigated. Studies were also done on the application of SnO2 nanowire films for UV light detection. ITO nanowires were grown via a self-catalytic VLS growth mechanism by electron beam evaporation without the use of any catalyst at a low substrate temperature of 250-400 °C. The influence of deposition parameters such as the growth temperature, oxygen partial pressure, evaporation rate of ITO, and growth duration has been investigated. Preliminary studies have been done on the application of ITO nanowire films for transparent conducting coatings as well as for antireflection coatings. The final part of the work is on the Au-assisted and self catalytic growth of SnO2 and In2O3 nanowires on Si substrates by resistive thermal evaporation. For the first time, SnO2 nanowires were grown with a Au-assisted VLS mechanism by the resistive thermal evaporation method at a low substrate temperature of 450 °C. SEM, XRD, XPS, TEM, and EDS studies on the grown nanowires showed that they were single crystalline in nature and free of impurities. Studies were also made on the application of SnO2 nanowire films for methanol sensing. The self-catalytic growth of SnO2 and In2O3 nanowires were deposited in high vacuum (5×10-5 mbar) by thermal evaporation using a modified evaporation source and a substrate arrangement. With this arrangement, branched SnO2 and In2O3 nanowires were grown on a Si substrate. The influence of deposition parameters such as the applied current to the evaporation boat, and oxygen partial pressure has been investigated. The growth mechanism behind the formation of the branched nanowires as well as nanowires has been explained on the basis of a self-catalytic vapor-liquid-solid growth mechanism. The highlight of this thesis work is employing e-beam evaporation and resistive thermal evaporation methods for nanowire growth at low substrate temperatures of ~ 300-500 °C. The grown nanowires were tested for applications such as gas sensing, transparent conducting coatings, UV light detection and antireflection coating etc. The thesis is divided into nine chapters and each of its content is briefly described below. Chapter 1 In this chapter, a brief introduction is given on nanomaterials and their applications. This chapter also gives an overview of the different techniques and different growth mechanisms used for nanowires growth. A brief overview of the applications of semiconductors and semiconductor oxide nanowires synthesized is also presented. Chapter 2 Different experimental techniques employed for the growth of Si, Ge, SnO2, In2O3, ITO nanowires have been described in detail in this chapter. Further, the details of the different techniques employed for the characterization of the grown nanowires were also presented. Chapter 3 In this chapter, studies on the growth of Germanium nanowires by electron beam evaporation (EBE) are given. The influence of deposition parameters such as growth temperature, evaporation rate of germanium, growth duration, and catalyst layer thickness was investigated. The morphology, structure, and composition of the nanowires were investigated by XRD, SEM, and TEM. The VLS growth mechanism has been discussed for the formation of the germanium nanowires by EBE using Au as a catalyst. Chapter 4 This chapter discusses the growth of Si nanowires with Indium and Bismuth as an alternate to Au-catalyst by electron beam evaporation. The influence of deposition parameters such as growth temperature, Si evaporation rate, growth duration, and catalyst layer thickness has been investigated. The grown nanowires were characterized using XRD, SEM, TEM and HRTEM. The Silicon nanowires growth mechanism has been discussed. Chapter 5 This chapter discusses the Au-catalyzed VLS growth of SnO2 nanowires by the electron beam evaporation method as well as Antimony doped SnO2 nanowires by co-evaporation method at a low substrate temperature of 450 °C. The grown nanowires were characterized using XRD, SEM, TEM, STEM, Elemental mapping, HRTEM, and XPS. The effect of deposition parameters such as oxygen partial pressure, growth temperature, catalyst layer thickness, evaporation rate of Sn, and the growth duration of nanowires were investigated. The SnO2 nanowires growth mechanism has been explained. Preliminary studies were made on the possible use of pure SnO2 and doped SnO2 nanowire films for UV light detection. SnO2 nanowire growth on different substrates such as stainless steel foil (SS), carbon nanosheets films, and graphene oxide films were studied. SnO2 nanowire growth on different substrates, especially SS foil will be useful for Li-ion battery applications. Chapter 6 This chapter discusses the self catalyzed VLS growth of Sn doped Indium oxide (ITO) nanowires by the electron beam evaporation method at a low temperature of 250-400 °C. The grown nanowires were characterized using XRD, SEM, TEM, STEM, HRTEM, and XPS. The effect of deposition parameters such as oxygen partial pressure, growth temperature, evaporation rate of ITO, and the growth duration of the nanowires were investigated. Preliminary studies were also made on the possible use of self-catalyzed ITO nanowire films for transparent conducting oxides and antireflection coatings. ITO nanowire growth on different and large area substrates such as stainless steel foil (SS), and Glass was done successfully. ITO nanowire growth on different substrates, especially large area glass substrates will be useful for optoelectronic devices. Chapter 7 In this chapter, studies on the growth of SnO2 nanowires by a cost-effective resistive thermal evaporation method at a relatively lower substrate temperature of 450 °C are presented. The grown nanowires were characterized using XRD, SEM, TEM, HRTEM, and XPS. Preliminary studies were done on the possible use of SnO2 nanowire films for methanol sensing. Chapter 8 This chapter discusses the self-catalytic growth of SnO2 and In2O3 nanowires by resistive thermal evaporation. The nanowires of SnO2 and In2O3 were grown at low temperatures by resistive thermal evaporation using a modified source and substrate arrangement. In this arrangement, branched SnO2 nanowires, and In2O3 nanowires growth was observed. The grown nanowires were characterized using XRD, SEM, TEM, HRTEM, and XPS. The possible growth mechanism for branched nanowires growth has been explained. Chapter 9 The significant results obtained in the present thesis work have been summarized in this chapter.