Thermal reactions and flash photolysis are used to study the olefin bond-migration promoted by tungsten carbonyls. Substitution of piperidine (pip) by 2- allylphenyldiphenylphosphine (adpp) in the cis-(pip)(η^1- adpp)W(CO)-4 complex was investigated, and no olefin bond-migration was observed. This suggests that a vacant coordinated site adjacent to the coordinated olefin is an essential requirement for olefin bond rearrangement. The rates of olefin attack on the photogenerated coordinatively unsaturated species, cis-[(CB)(η^1-ol- P)W(CO)-4] (CB = chlorobenzene, p-ol = Ph-2P(CH-2)-3CH=CH-2; n = 1-4) were measured. Kinetics data obtained both in pure CB and in CB/cyclohexane mixtures support a dissociative mechanism in which the W-CB bond is broken in the transition state. In contrast to results observed in studies of other related systems, no olefin bond-migration is noted. This observation is attributed to P-W coordination at all stages of the reaction, which precludes formation of a reactive intermediate containing a vacant coordination site adjacent to a P-ol bond.

Ru-catalyzed olefin metathesis is an exceptionally powerful, versatile methodology for the assembly of carbon–carbon bonds. The N-heterocyclic carbene (NHC)-stabilized, “second-generation” Ru catalysts have enabled groundbreaking recent advances, ranging from the RCM assembly of cyclic peptides as hepatitis C virus therapeutics, to the elaboration of renewable seed oils and phenylpropanoids into value-added products and chemicals. However, key limitations arise from facile catalyst decomposition. Despite a plethora of studies on the synthesis of new catalysts, and on the decomposition processes accessible to the precatalyst and resting-state species, the underlying principles that govern decomposition of the active intermediates have been surprisingly little examined. One important reason for this is their incredible reactivity: the four-coordinate methylidene intermediate RuCl2(H2IMes)(=CH2) is too short-lived to be observed, while the metallacyclobutane (MCB) intermediate RuCl2(H2IMes)(2-C3H6) can only be observed below –40 °C. This makes them extremely challenging, but also fascinating targets for study. Understanding the underlying chemistry that dictates their reactivity and decomposition is essential for informed catalyst and process redesign, and is thus of fundamental interest, but also considerable practical importance. This thesis work thus aims at understanding the decomposition of active intermediates relevant to the highly-active, second-generation class of catalysts. Emphasis is placed on examining a variety of metathesis contexts, as well as providing solutions. Treated first are the decomposition pathways that arise during metathesis of electron-deficient olefins, a frontier area in organic synthesis, and in the utilization of renewable resources. An unexpected correlation is revealed between rapid catalyst decomposition, and the presence of a stabilizing PCy3 ligand in the standard catalyst for this reaction. The nucleophilic phosphine ligand is shown to attack an acrylate olefin, forming enolates that function as potent Brønsted bases. Literature evidence suggests that such strong bases are innocuous towards the precatalyst, pointing towards a key role for the active intermediates in Brønsted base-induced catalyst decomposition. Precisely which intermediate is involved, as well as the site of deprotonation, is elucidated next. Prior to this work, the NHC ligand was widely believed to be the target for attack. However, through labelling experiments, analysis of the Ru and organic byproducts, and computational studies, deprotonation is shown to occur at the MCB ring. Moreover, MCB deprotonation is revealed to be unexpectedly general, and not contingent on the presence of either an exceptionally strong base, or an electron-deficient substrate. This understanding is key, given recent reports from pharma highlighting the adverse impact of base contaminants, as well as current interest in metathesis of amine-containing substrates. Next examined are the intrinsic decomposition pathways operative for the MCB and four-coordinate methylidene. Prior to this work, the only reported pathway for decomposition of these two species involved beta-elimination of the MCB ring as propene. However, beta-elimination is shown to play an unexpectedly minor role in catalyst decomposition: less than 40% propenes are observed, even under conditions expected to favour MCB elimination. Bimolecular coupling of the methylidene, with loss of the methylidene moiety as ethylene, is proposed to account for the difference. Thus, transiently-stabilized adducts RuCl2(H2IMes)(=CH2)(L)n (L = o-dianiline or pyridine) are synthesized at temperatures down to –120 °C. On warming, these adducts lose Ln and rapidly decompose via bimolecular coupling, with loss of the methylidene moiety as ethylene. These experiments provide the first unambiguous evidence for bimolecular coupling in the important "second-generation" Ru systems, nearly two decades after which this pathway was dismissed in leading papers and reviews. The last two sections focus on solutions. First, a powerful, straightforward solution to the “enolate problem” is developed, whereby the acrylate enolates are quenched and sequestered via reaction with a polyphenol resin. Then, methods for preventing catalyst decomposition during matrix-assisted laser desorption / ionization mass spectrometry (MALDI-MS) are developed, via elucidation of the instrumental and experimental factors that promote successful analysis. As one of the only MS methods capable of affording insight into neutral metal complexes and catalysts, MALDI has unique potential to enable routine analysis of catalyst speciation and decomposition in situ, under real catalytic conditions, for a wide range of catalytic reactions. Collectively, the findings in this thesis offer a much more complete understanding of the fundamental pathways accessible to the important, highly-active metathesis intermediates, and offer strategies likely to inform practice in both academic and industrial settings. This understanding is key to harnessing the full potential of metathesis methodologies.

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No description available.

As hydrogel products are manufactured and used for applications ranging from biomedical to agricultural, it is useful to characterize their behavior and interaction with other materials. This thesis investigates the adhesion between two different solvated semi-interpenetrating polymer network (S-IPN) silicone hydrogels and a cyclo-olefin (COP) polymer through experimental, analytical, and numerical methods. Interfacial fracture data was collected through the application of the wedge test, a relatively simple test allowing for the measurement of fracture properties over time in environments of interest. In this case, the test was performed at discrete temperatures within range of 4Ë C to 80Ë C. Two COP adherends were bonded together by a layer of one of the S-IPN silicone hydrogels. Upon the insertion of a wedge between the two adherends, debonding at one of the two interfaces would initiate and propagate at a decreasing rate. Measurements were taken of the debond length over time and applied to develop crack propagation rate versus strain energy release rate (SERR) curves. The SERR values were determined through the application of an analytical model derived for the wedge test geometry and to take into account the effects of the hydrogel interlayer. The time-temperature superposition principle (TTSP) was applied to the crack propagation rate versus SERR curves by shifting the crack propagation rates with the Williams-Landel-Ferry (WLF) equation-based shift factors developed for the bulk behavior of each hydrogel. The application of TTSP broadened the SERR and crack propagation rate ranges and presented a large dependency of the adhesion of the system on the viscoelastic nature of the hydrogels. Power-law fits were applied to the master curves in order to determine parameters that could describe the adhesion of the system and be applied in the development of a finite element model representing the interfacial fracture that occurs for each system. The finite element models were used to validate the analytical model and represent the adhesion of the system such that it could be applied to future geometries of interest in which the S-IPN silicone hydrogels are adhered to the COP substrate. <i>[Files modified per J. Austin, July 9, 2013 Gmc]</i> / Master of Science

No / In tensile stretching, many polymers undergo strain localization. The geometrical form of the localization can take the form of either a shear band or an approximately symmetric neck. We present a constitutive model of the early stages of deformation that predicts which form the localization will take. The model consists of an Eyring process acting with a Gaussian network that is implemented numerically. A Levy-Mises flow rule associated with the Eyring process has a tendency to produce shear bands. A relatively stiff Gaussian network is used in a model of polycarbonate that ensures that most of the strain is taken up by the Eyring process, resulting in shear banding. In contrast, a relatively soft Gaussian network is used in a model of polyethylene, which takes up the greater part of the strain, resulting in a neck. The predictions are compared with experiments. For polyethylene, a two-Eyring-process model is introduced for better accuracy.

This diploma thesis is focused on the preparation of enantiomerically pure compounds based on organocatalytic allylic substitution using Baylis-Hillman carbonates. As selected substrates for the allylic substitution were chosen α-azidoketones such as azidoacetophenone, 2-azido-1-indanone and then heterocyclic compounds (N-phenylrhodanine and its derivate) belonging to the pharmaceutical privileged compounds. Other substrate for allylic substitution was allylmalononitrile. In addition, this thesis includes with synthesis of cyclic compounds based on the reaction of products of allylmalononitrile with B-H carbonates using olefin metathesis.

Doctor of Philosophy / Department of Chemistry / Duy H. Hua / Carbon nanotubes are allotropes of carbon comprising of one or more grapheme sheets seamlessly joined together to form a cylinder. They are classified as single-walled carbon nanotubes (SWNTs) or multi-walled carbon nanotubes (MWNTs). They have potential applications ranging from conductive and high reinforcement material components, nano interconnection in electronic devices to drug delivery in biological systems. Current methods of production are high temperature arc-discharge, laser ablation of graphitic materials and chemical vapor deposition. These methods give tubes that are impure and highly heterogeneous in length, diameter and chirality thus leading to mixture metallic and semiconducting tubes. Effective application of such carbon nanotubes requires cumbersome, harsh and expensive purification and sorting into like forms. Such treatments usually compromised the structural integrity of the tubes and hence their mechanical and electrical properties. Also pristine carbon nanotubes are insoluble in most solvents. Solubility in basic organic solvents is crucial prior to their application, which requires some level of chemical manipulation or functionalization on the tubes. Currently methods of functionalization are unpredictable and limited to few oxidation reactions. A novel rational synthetic chemical approach to [12, 12] arm-chair carbon nano tube with pre-defined diameter and length has been explored utilizing cheap and simple organic building blocks and results achieved so far have been presented in this dissertation. Two approaches were employed to form the carbon-rich beltene (32) before its final conversion to the target single-walled carbon nanotube (SWNT) 1. A survey on carbon nanotubes and their related structures including their potential applications and properties are presented in chapter 1. In the second chapter an iron template-assisted olefin metathesis via a ferrocene intermediate served as an anchor for an effective cyclization. In chapter 3, an un-assisted olefin metathesis pathway was explored. Both approaches use a series of benzyl halide carbonylation coupling and Diels-Alder reactions to synthesize some of the key intermediates. The protocol presented in this dissertation may be used to produce functionalized carbon nanotubes with predefined length and diameter tailored for specific applications to be produced in kilogram scale for the first time since its discovery in 1991. Such an approach is expected to address most if not all of the problems associated with the traditional methods of producing carbon nanotubes.

Les molécules chirales représentent environ 60% des médicaments présents sur le marché pharmaceutique et plus de 80% des médicaments en développement avec plus de 150 milliards de dollars de chiffre d’affaire pour l’année 2002. Les intermédiaires chiraux sont fortement demandés dans l’industrie pharmaceutique atteignant 15 milliards de dollars de chiffre d’affaire en 2009. D’autres domaines en sont demandeurs avec une répartition d’environ 15% dans l’agrochimie et 5% pour la parfumerie. L’obtention de composés d’intérêt pharmaceutique de façon asymétrique est un réel défi et une réelle nécessité. Ces molécules possèdent une architecture spatiale qui entraîne des interactions spécifiques et des affinités particulières avec les enzymes ou des récepteurs biologiques chiraux. L’utilisation de catalyseurs pour accéder à des composés organiques chiraux et plus précisément l’oxydation d’alcanes prochiraux ou d’oléfines constitue un domaine en essor ces dernières décennies. Pour parvenir à synthétiser des molécules chirales, l’industrie pharmaceutique s’est tournée vers l’utilisation de biocatalyseurs en partie pour réaliser différentes réactions stéréo-contrôlées avec la nécessité de séparer les mélanges racémiques par résolution enzymatique. Cependant, les biocatalyseurs présentent un inconvénient majeur qui est généralement le faible rendement en composé chiral recherché et nécessite un savoir faire pour la manipulation de ces enzymes. Les métalloporphyrines sont des catalyseurs comportant un macrocycle tétrapyrrolique et différentes fonctionnalisations en positions méso. Ces molécules ont fait l’objet de nombreuses études qui ont conduit à la synthèse de métalloporphyrines chirales très complexes. Malheureusement, leur synthèse est souvent longue avec de faibles rendements et leur application à un nombre limité de substrats ne permet pas leur généralisation. Ce travail de thèse, développé pour la première fois au laboratoire, s’inscrit dans le cadre d'un contrat CIFRE, dans le but de parvenir à la synthèse de porphyrines chirales facilement accessibles, applicables dans des réactions d’oxydation énantiosélectives efficacement (stabilité). Le premier objectif visé est la synthèse de porphyrines chirales dont la structure ciblée comporte des groupements hétérocycliques azotés chiraux en position méso, reliés par une liaison carbone-hétéroatome (C-N). Nous avons pu atteindre 4 séries de porphyrines qui ont été évaluées dans des réactions d’oxydation énantiosélectives (époxydation, hydroxylation). Le deuxième objectif visé est d’exploiter les propriétés électroniques particulières des porphyrines permettant l’application des porphyrines en tant que photosensibilisant après photoactivation en thérapie anticancéreuse. L’étude des paramètres physiques est primordiale pour déterminer la longueur d’onde d’activation et le rendement quantique. Nous avons souhaité utiliser nos porphyrines et leurs précurseurs en tant qu’agents antiparasitaires, sans photoactivation dans un premier temps, conduisant à la découverte d’activités très intéressantes sur certaines espèce de leishmanies. Enfin, leur application sur P. falciparum nous a permis d’isoler une molécule avec une activité très intéressante. Dans les deux cas, des manipulations avec photoactivation sont en cours. / Chiral molecules represent about 60% of drugs in pharmaceutical market and over 80% of drugs in development with more than 150 billion dollars in 2002. Chiral intermediates are in high demand in the pharmaceutical industry producing a turnover of 15 billion dollars in 2009. Other areas are seekers of chiral molecules with a distribution of about 15% in agrochemicals and 5% for the perfume. Asymmetrically production of compounds of pharmaceutical interest is a real challenge. These molecules have a spatial architecture that results in specific interactions and affinity with the enzymes or biological chiral receptors. The use of catalysts to synthesis chiral organic compounds, and more specifically to oxidize alkenes and alkanes having prochiral positions, is a very important area extensively studied in recent decades with few positive results. To achieve the synthesis of chiral molecules, the pharmaceutical industry has turned to the use of biocatalysts, in part, to perform various stereo-controlled reactions with systematically followed by separation of the different isomers by different methodes. However, biocatalysts have a major disadvantage relative to low yields of chiral compound and requires expertise for handling these enzymes. Metalloporphyrins are tetrapyrrolic macrocyle substituted in meso position with various functional groups and incorporating metals (Fe, Mn, Co, Ru). These molecules have been extensively studied and led to the synthesis of many complex chiral metalloporphyrins. Unfortunately, their synthesis is often long with low yields and their application to a limited number of substrates is a major drawback. The first objective of this work is the synthesis of original chiral porphyrins. The targeted structure contains chiral heterocyclic nitrogen groups in two meso positions, connected by a carbon-heteoatom bond (C-N). We were able to reach 4 porphyrins-series that have been evaluated as catalyst in oxidation reactions (epoxidation, hydroxylation). The second objective is to take advantage of specific electronic properties of porphyrins for applications as photosensitizer after photoactivation for cancer by photodynamic therapy. The use of this therapy increased during last decades but poor specificity and solubility of the different porphyrins used in clinic against many cancers prompt us to investigate this area. The study of the physical parameters is essential to determine wavelength activation and quantum yield of a photosensitizer. We wanted to use our porphyrins and their precursors as antiparasitic agents, with and without photoactivation against L. donovani, L. major, T. brucei brucei. Malaria is caused by a protist of the genus of Plasmodium. This parasite has an iron deficiency on one hand and cannot biosynthesize certain amino acids. Strucure analogy of porphyrins with heme led us to evaluate antimalarial activity of several porphyrins against P. falciparum.

Nesta Dissertação, foram realizadas reações de copolimerização de 1,3-butadieno com diferentes alfa-olefinas (1-hexeno, 1-octeno e 1-dodeceno) utilizando-se um sistema catalítico do tipo Ziegler-Natta ternário constituído por versatato de neodímio, hidreto de diisobutilalumínio e cloreto de t-butila. O sistema catalítico também foi avaliado em reações de homopolimerização com cada alfa-olefina. As condições reacionais, tanto da síntese do catalisador como das reações de polimerização, foram mantidas constantes. Foi estudada a influência de diferentes teores de cada alfa-olefina (1, 3, 5, 10, 20 e 30 % em relação ao 1,3-butadieno) sobre a conversão da polimerização, a microestrutura, a massa molar, as propriedades viscosimétricas e a estabilidade térmica dos polímeros obtidos. Foi avaliada, ainda, a influência do tamanho da cadeia da alfa-olefina sobre as características da polimerização. Os polímeros foram caracterizados por espectroscopia na região do infravermelho (FTIR), cromatografia por exclusão de tamanho (SEC), viscosimetria capilar e termogravimetria (TG). A microestrutura dos polímeros, praticamente, não variou com a adição das alfa-olefinas. A massa molar numérica média (Mn) não sofreu alterações significativas, enquanto que a massa molar ponderal média (Mw) apresentou tendência ao aumento, quanto maior foi a incorporação de comonômero. A viscosidade intrínseca não apresentou uma tendência com a adição da alfa-olefina na reação, permanecendo na faixa de 2,015 a 3,557 dL/g. A estabilidade térmica do copolímero mostrou uma tendência a aumentar com a incorporação das alfa-olefinas / In this work, were performed copolymerization reactions of 1,3-butadiene with different alpha-olefins (1-hexene, 1-octene and 1-dodecene), using a ternary catalytic system of Ziegler-Natta, constituted by neodymium versatate, diisobutylaluminum hydride and t-butyl chloride. The catalytic system was also evaluated in homopolymerization reactions with the alpha-olefins. The reaction conditions, both the catalyst synthesis as the polymerization reactions, were kept constant. The influence of different content of each alpha-olefin (1, 3, 5, 10, 20 and 30% compared to 1,3-butadiene) on the polymerization conversion, the microstructure, molar mass, viscometric properties and thermal stability of polymers was studied. The influence of alpha-olefin chain size on polymerization characteristics was also evaluated. The polymers were characterized by infrared spectroscopy (FTIR), size exclusion chromatography (SEC), capillary viscometry and thermogravimetry (TG). The polymer microstructure, practically, did not change with the addition of alpha-olefins. The number average molecular mass (Mn) has not changed; while the weight average molecular mass (Mw) trended to increase. The intrinsic viscosity did not show a trend with the alpha-olefin addition, remaining in the range from 2.015 to 3.557 dL/g. The copolymer thermal stability showed a tendency to increase with the incorporation of alpha-olefins