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This thesis covers the development of catalytic methodologies for the mild and chemoselective reductions of amides. The first part of the thesis describes the use of a Fe(II)/NHC catalyst for the deoxygenation of aromatic tertiary amides to corresponding amines. The protocol is characterized by low catalyst loading, mild reaction conditions and the use of air and moisture stable polymethylhydrosilaxane (PMHS) as the hydride source. The second part concerns the development of a protocol for the room temperature deoxygenation of a wide range of tertiary amides to amines using catalytic amounts of Et2Zn and LiCl together with PMHS. The system displayed high levels of chemoselectivity tolerating various reducible groups such as nitro, nitrile, and olefin functionalities, and was shown to be applicable for the reduction of aromatic, heteroaromatic and aliphatic tertiary amides. The attempts to expand the scope of the Fe-based protocol to accommodate benzylic tertiary amides led to the development of a transition metal-free catalytic system based on KOtBu for the formation of enamines. The final products constitute an important class of precursors for a wide range of valuable compounds in organic chemistry. Moreover, avoiding the use of transition metals in the protocol allowed the desired products to be obtained without the hazardous metal contaminants. The last chapter of the thesis describes the Mo(CO)6-catalyzed hydrosilylation of amides. The Mo-based catalyst was proven to mediate the deoxygenation of α,β-unsaturated tertiary and secondary amides to the corresponding allylamines without reduction of the olefinic bonds. Further development of the catalytic system revealed an unprecedented chemoselectivity in the hydrosilylation of aromatic and certain aliphatic tertiary amides in the presence of a variety of reducible groups along with aldehydes and imines that were tolerated for the first time. Moreover, it was possible to control the reaction outcome by variation of the reaction temperature to obtain either amines or aldehydes as the major products. The synthetic utility of the developed Mo(CO)6-catalyzed protocols was further demonstrated in the synthesis of the pharmaceuticals Naftifine and Donepezil.

The amine-activated iron-catalysed hydrosilylation of alkenes and alkynes has been developed, and has been found to selectively provide the anti-Markovnikov product. It was established that a range of amines could be used to activate an iron(II) pre-catalyst containing triflate counter ions in situ, with diisopropylethylamine facilitating the highest reactivity (Scheme A1). Pre-catalyst and amine loadings as low as 0.25 mol% and 1 mol%, respectively, could be used for the gram-scale hydrosilylation of 1-octene with phenylsilane, in air. The activator-free iron- and cobalt-catalysed hydrosilylation of alkenes and alkynes was subsequently established, by using pre-catalysts containing tetrafluoroborate counter ions. The methodology was extended to the hydroboration and hydrogenation of olefins. The activation has been proposed to occur via the in situ formation of a hypervalent silicon ‘ate’ complex, formed as a result of the hydrolysis of the BF4 - counter ion. It was found that the iron-catalysed system provided anti-Markovnikov hydrosilylation products, whereas Markovnikov products were formed preferentially when using the cobalt pre-catalyst (Scheme A2). Consequently, the regioselectivity of hydrosilylation could be easily altered.

Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Chemistry." Includes bibliographical references (p. 236-254).

Selective 1,2-hydrosilylation of 1,3-dienes is a challenging problem to solve for transition metal catalysis. Butadiene, specifically, would be a useful substrate because 3-butenylsilane products have promise as superior coupling reagents for hybrid organic/inorganic materials synthesis. In this thesis, we describe the first selective 1,2-hydrosilylation of conjugated dienes, including butadiene. / Chemistry and Chemical Biology

Thesis (PhD)--University of South Australia, 1996

Carbosilane dendrimers have been prepared via iterative hydrosilylation/alkenylation reactions using a variety of chlorosilanes (HSiMe₃₋nC1n)and alkenyl nucleophiles (CH₂=CHCH₂MgBr and CH₂=CHMgBr). Characterization by multinuclear NMR spectroscopy of the stepwise trifurctate dendrimers RED₃ (E=Si; R=Ph; D=Dendritic carbosilane fragment) assists end-group counting (NMR, R vs D) and can be related to analogous spheroidal ED₄ and hexafunctional E₂D₆ systems (E=Si or Ge). Typical D units contain (prnSiMe₃₋n)N Nb linkers; where pr=(CH₂)₃, N=generation number, Nb=branch multiplicity at silicon. For higher symmetry ED₄ and E₂D₆ systems (and also trifurcate) the Nb=1 (1B series) or Nb=2 (2B series) also allows for end-group counting by proton NMR spectroscopy (Ph:D:Me). ²⁹Si NMR chemical shifts have been developed for topographical mapping of dendritic structure. Peripheral and core substitution reactions have been examined for a series of trifurcate and related Ge₂D₆ ‘masked trifurcate' dendrimers. Replacement of end groups with a range of substrates is facilitated by the reactivity of the intermediate silicon chlorine bonds formed by hydrosilylation reactions. Selective removal of the core phenyl group (via triflic acid), or alternatively oxidative Ge-Ge cleavage, allows for unprecedented ‘bifunctionalization’; offering routes into dendrimer periphery:core electron transfer (‘photon-harvesting’) processes. Methodology for a ‘rapid-synthesis’ of hyperbranched structures has been developed and examined on a range of initial core molecules. Use of multinuclear NMR spectroscopy via comparison with step-wise products, as well as GPC chromatography, gives some insight into the overall architectures produced. Alteration of Si branch point from Nb=2 to Nb=3, using presynthesised ‘hypercores’ facilitates an alternate method of end group counting for higher symmetry cores. This methodology allows for population counting at large N in dendrimer generation G(N) (D interior vs D periphery). / Graduate

L’objectif principal de cette thèse a été de développer de nouveaux systèmes catalytiques efficaces pour la dépolymérisation de la biomasse et des plastiques. La stratégie choisie pour favoriser cette transformation a été l’hydrosilylation de liaisons C-O. Le catalyseur d’iridium(III) de Brookhart s'est révélé particulièrement efficace pour l’hydrosilylation la lignine conduisant à des produits aromatiques purs avec des rendements très élevés. Il a également été utilisé pour la dépolymérisation réductrice de plastiques oxygénés qui ont permis d’isoler les monomères et des composés de haute valeur ajoutée.Dans un second temps, une dépolymérisation plus « verte » de polycarbonates et de polyesters a été mise en œuvre. Celle-ci ne fait intervenir ni métaux ni solvant grâce à l’utilisation du fluorure de tetra-n-butyle amonium comme catalyseur. Enfin, l’uranium appauvri, considéré comme un déchet de l’industrie nucléaire, a été valorisé comme catalyseur pour la réduction des liaisons C-O. Il a été découvert qu’un complexe de triflate d'uranyle favorisait efficacement le couplage réducteur de l'aldéhyde en présence d'hydrosilanes conduisant à l'éther symétrique. / The main objective of this thesis is the development of new efficient catalytic systems for the depolymerization of biomass and plastics. The chosen strategy to promote such transformations was the hydrosilylation of C-O bonds. Brookhart's iridium(III) catalyst was found to be very effective for hydrosilylation of lignin leading to pure aromatic products isolated in very high yields. It was also used for the reductive depolymerization of oxygenated plastics, allowing the isolation of monomers and valuable chemicals.In a second step, a "greener" depolymerization of polycarbonates and polyesters was implemented. This does not involve metals or solvents through the use of tetra-n-butyl amonium fluoride as a catalyst for hydrosilylation. Finally, depleted uranium, considered as a waste product of the nuclear industry, was valorized as a catalyst for the reduction of C-O bonds. It has been discovered that a uranyl(VI) triflate complex efficiently promotes reductive coupling of the aldehyde in the presence of hydrosilanes leading to symmetric ethers.

La détection rapide et sensible des agents pathogènes est d’une très grande importance pour la biosécurité. Les biopuces sont bien adaptées à cet effet, car elles permettent la détection multiplexe des cibles. Une limitation cruciale des biopuces est leur manque de fiabilité et de sensibilité. L’objectif de cette thèse est de développer une architecture reproductible de biopuces à base de couche mince de silicium amorphe carboné (a-SiC:H) déposée sur un réflecteur en aluminium pour une détection fiable et sensible des pathogènes. Nous avons choisi comme système modèle l’interaction de la toxine alimentaire ochratoxine A (OTA) avec son aptamère AntiOTA de longueur 36mer. Les aptamères (simples brins d’ADN) sont de plus en plus utilisés comme sondes en raison de leur grande spécificité et affinité vis-à-vis d’une large gamme de cibles (i.e. protéines, bactéries…). La stratégie de fabrication consiste en un greffage de monocouches organiques d’acides carboxyliques via des liaisons Si-C robustes, suivi de l’accrochage covalent des aptamères par un couplage peptidique. Les processus de greffage ont été mis au point sur silicium cristallin permettant la quantification des couches greffées par spectroscopie infrarouge en mode ATR (Attenuated total reflexion). La quantification IR des interactions OTA – AntiOTA a été montrée pour la première fois sur des surfaces par IR-ATR. La spécificité de l’aptamère a été démontrée en utilisant une molécule chimiquement similaire (warfarin), pour laquelle l’AntiOTA ne montre aucune affinité. Ces protocoles bien contrôlés ont été transférés sur l’architecture de la biopuce a-SiC:H. Les aptamères immobilisés sont hybridés avec des brins complémentaires marqués avec des fluorophores. En présence de l’OTA une déshybridation des brins complémentaires est attendue, conduisant à une diminution du signal fluorescent. Différentes longueurs de brins complémentaires ont été comparées, montrant jusqu’à 13% de diminution due à l’interaction de l’OTA. / Rapid and sensitive detection of pathogenic targets play a crucial role in biosecurity. Biochips are ideal for this, as they allow easy and multiplex detection of targets. A crucial limitation in biochips is that they often suffer from low reliability and sensitivity. The goal of this thesis is to develop a stable and reproducible architecture for biochips based on an amorphous silicon carbon alloy (a-SiC:H) deposited on an aluminium back-reflector for reliable and sensitive detection of pathogens. On these biochips we introduced the interaction of the food and feed toxin ochratoxin A (OTA) with its 36mer aptamer AntiOTA as a model system. Aptamers (single strands of DNA) are ideal as probes for biochips as they display high specificity and affinity towards a wide range of targets (i.e. proteins, bacteria…). The well-controlled multi-step fabrication process consists of the reliable photochemical grafting of acid-terminated organic monolayers on silicon surfaces by robust Si C bonds, which in turn were functionalized with aptamers by stable peptide coupling. Carrying out this process on crystalline silicon allowed monitoring and quantification of every step by infrared spectroscopy (IR-ATR). The interaction OTA – AntiOTA was shown for the first time on surfaces by IR, and an IR in situ calibration allowed the quantification of OTA which was bound by the aptamers on the surface. The specificity of AntiOTA towards OTA was demonstrated by using a chemically similar molecule (warfarin), for which AntiOTA shows no affinity. The well-controlled protocols were transferred to the a-SiC:H biochip. The immobilized aptamers were hybridized with complementary and fluorescent-labeled DNA-strands. In presence of OTA, dehybridization of the complementary strands is expected, resulting in a decrease of fluorescent signal. Different lengths of complementary strands were compared, exhibiting up to 13% signal decrease due to OTA.

Thèse de doctorat : Sciences chimiques. Polymères : Bordeaux 1 : 2009. / Titre provenant de l'écran-titre.