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Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

Asymmetric conjugate addition of bis(pinacolato)diboron followed by aldol cyclisation of enone diones under the action of a chiral copper catalyst has been developed. This enantioselective process, using a chiral bisphosphine as ligand, allows the formation of bicyclic alcohols with four contiguous stereocentres in high diastero- and enantioselectivity. This catalytic system has been applied to the parallel kinetic resolution of a racemic β- ketoamide. Further functionalization of the bicyclic alcohols synthesised was also possible. A domino addition of arylboronic acids and cyclisation of alkynones via an undescribed iridium 1-4-migration process has been developed. A range of tricyclic compounds using a variety of arylboronic acids have been synthesised in good yields and high diasteroselectivity. The use of chiral bisphosphine ligand together with an iridium salt allows the formation of enantioenriched compounds in moderate yield.

Supramolecular chemistry allows the rapid formation of complex systems through self-assembly. These systems often possess unique properties not observed for conventional covalent constructs and have potential applications in areas such as sensing, drug delivery and catalysis. Metallosupramolecular container compounds have been shown to catalyse reactions with both regio- and stereo-selectivity in methods analogous to enzyme type catalysis. Separately, visible-light photoredox catalysis has recently gained considerable interest as an efficient, green and mild method for the rapid synthesis of many chemical compounds. In order to combine the favourable properties of both supramolecular catalysis and visible-light photoredox catalysis, a number of photoredox active metallosupramolecular assemblies were designed, synthesised and analysed. Initial steps were taken to stabilise a known iridium-based M6L4 luminescent cage compound to allow guest encapsulation to take place. The incorporation of isocyanide donors as strong ligands improved the stability of model compounds but synthesis of an analogous three-dimensional assembly was unsuccessful. Instead, a “complex-as-ligand” approach was taken that allowed the straight-forward formation of Pd2L4 systems from a range of photoactive iridium complexes. Importantly, unlike many other photoactive systems, the complexation to palladium did not drastically affect the photoredox properties of the constituent iridium complexes. Multiple approaches were then taken to improve both the stability and guest binding properties of the photoactive assembly in an effort to achieve supramolecular photoredox catalysis. Utilising a model system, a general method was thus developed for enhancing the association constants of neutral guests in organic solvents by switching to large, non-coordinating counter ions that provided reduced competition for the internal binding site. In combination with this increased binding affinity, a range of guest properties were adjusted by association with the hydrogen bond donor environment of the internal cavity. The encapsulation of quinone based oxidants led to unexpected and novel reaction pathways not observed in the bulk phase. As such, this work represents a significant advancement in development of metallosupramolecular systems capable of regio- and stereo-selective photoredox catalysis.

Transition edge sensors are the detectors of choice for a wide range of applications; from dark matter search, neutrino search, to cosmic radiation detection from near infrared to millimeter wavelengths. We are developing transition edge sensors using superconducting iridium thin films and we are proposing their use for future dark matter and neutrino search experiments. Our Ir films are deposited using an radio frequency (RF) magnetron sputtering and photolithographic techniques and measured using an adiabatic refrigerator capable of reaching temperatures of a few tens of mK. This thesis presents a detailed description of superconducting iridium thin films from the fabrication process to the characterization of the film properties at room temperature and low temperature. Alternative options for the bias circuit used to read out the TES signals will be discussed, we are proposing the use of RLC resonant circuits and transformers instead of SQUIDS.

The research described in this thesis focuses on the catalytic asymmetric hydrogenation of prochiral olefins using N, P – chelated iridium catalysts. This catalytic system is tolerant to a wide range of substrates and performs better than the well-known ruthenium- and rhodium-catalytic systems for substrates devoid of coordinating groups in proximity of the olefin. Low catalytic loadings (often <1 %) and the high atom efficiency of this reaction make it a synthetically useful method of chiral molecule synthesis. The primary aim of this thesis was to develop new catalysts that rapidly and efficiently hydrogenate a broad range of alkenes asymmetrically. Papers I and II describe the synthesis and evaluation of new, highly efficient, chiral N, P – ligated iridium complexes. These catalysts were obtained in relatively few steps, while leaving open possibilities to modify and fine-tune their structure. Their versatility is ideally suited to both industrial uses and to equip any catalyst box. Paper III deals with a common problem of defluorination of vinylic fluorides during the hydrogenation. The catalyst designed in that work performs well for several substrates giving very low defluorination rates making it a good starting point for further improvements to cover a broader scope of vinyl fluorides. The structures of the catalysts from papers I and III also offers an easy approach to attach the catalyst ligands to a solid support. Paper IV explores hydrogenation of vinyl boronates, which gives synthetically interesting borane compounds with high enantioselectivities. Taking into account the rich chemistry of organic boranes, these compounds are very important. Paper V deals with hydrogenation of diphenylvinylphosphine oxides and vinyl phosphonates, another important classes of substrates that give chiral phosphorous containing compounds of interest in many fields of chemistry: such as medicinal chemistry and organocatalysis. In papers VI and VII we explore the Birch reaction as a source of prochiral olefins. By combining asymmetric hydrogenation with it, we obtain a powerful method to create chiral compounds with excellent enantioselectivities that are next to impossible to make by other routes. The products of the asymmetric hydrogenation are further modified by other well-known transformation to create other induced stereogenic centres.

Hydrogenation of "largely unfunctionalized" alkenes has been an active area of research for about a decade. Many catalysts have been prepared but we noticed that comparatively few substrates have been studied and none of these hydrogenations provided useful chirons for the organic synthesis area. That motivated us to investigate asymmetric hydrogenations of chiral acyclic alkenes, which are seldom used for hydrogenations and usually the reactions are fully substrate controlled. It emerged that such reactions could provide a concise entry points into chirons that can be used to prepare many natural products. Asymmetric hydrogenations of functionalized, but not coordinatively functionalized, alkenes have been used to prepare several chirons for syntheses ofpolyketide natural products using our N,carbene Crabtree's catalyst analog. Starting from optically active starting materials (eg Roche esters, lactic acid, glyceraldehyde dimethyl ketals, amino acids), highly optically active chiral alkenes can be made in several steps with high yield. With the iridium catalyzed asymmetric hydrogenations, chiral ethers, 1,3-hydroxymethyl chiron, alpha-methyl-beta-hydroxy-gamma-methyl chiron, alpha-methyl-gamma-alkyl-gamma-amino acid can be obtained with high stereoselectivities. With those well developed methodologies, (-)-dihydromyoporone, (-)-spongidepsin, (-)-invictolide have been prepared with high efficiency. Not like the vinyl acetate, which can be hydrogenated quite well with many Rh catalysts, the alkyl vinyl ether does not have a coordination functional group nearby, hence it is a difficult substrate for asymmetric hydrogenation and there are relatively few iv reports. Also the simple alkyl enol ether is quite acid sensitive and the Pfatlz's type N,PIr catalysts cannot hydrogenate the simple alkyl enol ethers well under the standard hydrogenation conditions. We explored many alkyl enol ethers and found some of them can be hydrogenated efficiently (50 bar H2, 1 mol percent N,carbene-Ir catalyst, 25 degree C) with high enantioselectivities (up to 98 percent ee). This study led us to suspect that more protons were produced when N,P-Ir catalyst precursors were used relative to the corresponding carbene catalyst since the former only gave complex mixture when being used. DF calculations and several other experiments supported this postulation.

Asymmetric hydrogenation as a general route to polypropionates has been explored for allylic alcohols, acids, and derivatives, which has led to the generation of 2,4-dimethylated hexane derivatives. Quantitative yields in most cases and enantioselectivities greater than 98% were obtained. A remarkable stereofacial inversion was observed when an ester or acid was present in the allylic position instead of an alcohol or alcohol derivative. This led to the construction of all four diastereomers of the hexanol series from a single enantiomer of hydrogenation catalyst. Also described are an attempted synthesis of (-)-lardolure, a formal synthesis of the methyl ester portion of the preen gland extract from the domestic goose Anser anser, and a total synthesis of an extract from the fungi A. cruciatus. The synthesis of these compounds demonstrated shortcomings of the known catalyst system showing enantioselectivities for polymethylated compounds was high, while diastereoselectivity was low. Methodology to develop new N-heterocyclic carbene catalysts was developed using the cyanide coupling of aldimines to generate electronically tunable 1,3,4,5-tetraaryl complexes, and X-ray, IR, and calculations were used to elucidate their electronic characteristics. These studies indicate that the 4,5-positions have as great an influence on the metal-ligand bond as the 1,3-positions. In addition, they are among the most electron-donating 2- metalated N-heterocyclic carbenes found thus far. An intrinsic relationship between catalytic activity and electron donating ability was found in transfer hydrogenations.

Thesis (Ph.D.)--Brown University, 2008. / Source: Dissertation Abstracts International, Volume: 69-06, Section: B, page: 3583. Adviser: William Trenkle. Includes bibliographical references.

The efficient construction of complex organic molecules mandates that an assortment of methods for forming C-C bonds be available to the practicing synthetic chemist. The addition of carbon based nucleophiles to carbonyl compounds represents a broad class of reactions used to achieve this goal. Traditional methodology requires the use of stoichiometrically preformed organometallic reagents as nucleophiles in this type of reaction. However, due to the moisture sensitivity, excessive preactivation and inevitable generation of stoichiometric waste required for the use of these reagents, alternative methods have become a focus of the synthetic organic community. The research presented in this dissertation describes a new class of C-C bond forming reactions enabled through catalytic transfer hydrogenation. Here, the development and implementation of efficient green methods for carbonyl addition employing π-unsaturates as surrogates to preformed organometallic reagents is described. Additionally, this research describes the first systematic studies toward using alcohols as electrophiles in carbonyl allylation, propargylation and vinylation reactions. / text