This thesis concerns the use of various potent oxidants in organic synthesis. The main focus is directed at selectively introducing trifluoromethyl groups into compounds containing double or triple bonds. All reactions proceed under mild conditions and can in most cases be performed on the bench-top. We have developed three different procedures for transformations of activated alkenes and alkynes as well as quinones. In paper I the selective introduction of a trifluoromethyl group together with an oxygen functionality to double and triple bonds is demonstrated. Paper II is focused on the related chemoselective cyanotrifluoromethylation in which a cyano group is added instead of the oxygen functionality. Paper III describes a new procedure for C–H trifluoromethylation of quinones. Our studies on the mechanistic aspects of the above reactions are described in Paper IV. In these studies we investigated the ligand and substituent effects in Cu-catalyzed reactions. Paper V is focused on a conceptually new palladium-catalyzed allylic C–H acyloxylation of olefins under oxidative conditions. The procedure uses an inexpensive, safe and environmentally benign oxidant, sodium perborate, which is activated with acetic anhydride. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Submitted.</p>

Les mécanismes chimiques détaillés de combustion des carburants à basse température font intervenir un nombre important d'espèces et de réactions. Les logiciels de génération automatique permettent de faire face à cette complexité. Ces logiciels font appel à des corrélations permettant de prédire les propriétés thermodynamiques (enthalpies de formation, entropies et capacités calorifiques) et cinétiques (constantes de vitesse) associées aux espèces et aux réactions. Ces corrélations reposent cependant, généralement, sur un nombre limité de données de référence. Dans ce travail de thèse, nous avons utilisé une méthode faisant appel à la chimie quantique pour développer de nouvelles corrélations pour le logiciel de génération automatique EXGAS. En ce qui concerne les données thermodynamiques, des groupes de Benson associés aux fonctions hydroxyle et hydroperoxyle ont été évalués, ainsi que des énergies de liaison C-H, et O-H de fonctions hydroxyle et hydroperoxyle. En ce qui concerne les données cinétiques, nous nous sommes plus particulièrement intéressés aux réactions d'isomérisation des radicaux alkylperoxyles et hydroxyalkylperoxyles, ainsi qu'aux réactions de formation d'éthers cycliques. Nous avons également étudié l'impact de certaines règles de globalisation et introduit de nouvelles réactions pour rendre compte de la formation de produits de combustion jusqu'ici négligés ou sommairement prédits par les modèles. Les résultats obtenus ont été introduits dans des mécanismes chimiques détaillés générés par EXGAS. Ces mécanismes ont servi de base pour réaliser des simulations de la combustion du propane et du n-butane à basse température. Les résultats de ces simulations ont été comparés à des résultats expérimentaux récents afin de valider les calculs effectués. Les résultats des simulations ont montré que la prise en compte des nouvelles corrélations ainsi que la modification des règles de globalisation dans les mécanismes permettaient d'améliorer la prédiction de certains polluants mineurs pouvant avoir un impact sanitaire et environnemental majeur / Detailed chemical kinetic models for the low-temperature combustion of fuels involve a large number of species and reactions. Automatic generation of kinetic mechanisms is a powerful tool to deal with this complexity. These softwares are based on correlations that predict thermodynamic (enthalpies of formation, entropies and heat capacities) and kinetic (rate constants) properties associated with species and reactions. However, these correlations are generally based on a limited number of reference data. In this work, we used a method involving quantum chemistry to develop new correlations for EXGAS, a software for the automatic generation of kinetic mechanisms. For thermodynamic data, new Benson groups associated with hydroxyl and hydroperoxyl functions were evaluated. Bond dissociation energies of C-H bonds and O-H bonds of these groups were also evaluated. For the kinetic data, we focused our study on the isomerization reactions of alkylperoxyl and hydroxyalkylperoxyl radicals, and on the reactions of formation of cyclic ethers. We also studied the impact of some rules of globalization and introduced new reactions to account for the formation of minor combustion products usualy neglected or imperfectly predicted by the current models. The results obtained have been introduced into detailed chemical mechanisms generated by EXGAS. These mechanisms were used to simulate the combustion of propane and n-butane at low temperatures. The results of these simulations were compared with recent experimental results to validate the calculations. The simulations showed that taking into account the new correlations and the modifications of the rules of globalization in the mechanisms improved the prediction of some minor pollutants that can have major health and environmental impacts

A importância que a catálise representa para a sociedade pode ser vista em números: 90% dos processos da indústria química e mais de 20% de todos os produtos industriais comercializados no mundo utilizam uma ou mais etapas catalíticas. Assim, desenvolver catalisadores eficientes, ativos e seletivos é a solução para criar tecnologias mais limpas e sustentáveis. Além disso, reações químicas que geram novas ligações C-C estão entre as transformações mais relevantes na química orgânica e são a base desse trabalho. Os catalisadores de ródio apresentados aqui fazem parte de um trabalho minucioso de desenvolvimento, síntese e caracterização de nanopartículas e suportes magnéticos funcionais que foram utilizados em transformações de diversas moléculas. O estudo inicial com nanopartículas de ródio suportadas, em reações de hidrogenação do cicloexeno, serviu para a compreensão de como se comportam essas nanoestruturas e da influência que diferentes ligantes orgânicos e estabilizantes podem ter em uma aplicação catalítica bastante conhecida. O sistema catalítico mostrou-se bastante ativo e reutilizável,despertando o nosso interesse ao seu aperfeiçoamento para aplicação em reações de hidroformilação. Antes da síntese de catalisadores suportados, estudos com nanopartículasnão-suportadas mostraram que um sistema modificado pela adição de fosfinas era necessário para ativação do catalisador e que o estabilizante utilizado afetava a atividade catalítica. Assim, para possibilitar o ancoramento eficiente das espécies ativas, uma modificação da superfície do suporte magnético com a metildifenilfosfina foi realizada. A fosfina funcionalizada sobre o suporte viabilizou sua interação com as espécies ativas e evitou a sua lixiviação, possibilitando o reuso do catalisador. A reação de hidroformilação do oct-1-eno atingiu 96% de conversão e 82% de seletividade para aldeídos, em 6 horas a 80°C. A carga metálica do catalisador foi de apenas 0,2%. Buscando aumentar a eficiência na etapa de imobilização do metal e uma melhor atividade catalítica que possibilitasse o uso de substratos mais complexos, o suporte magnético foi modificado com um polímero hiper-ramificado. Essa modificação possibilitou aumentar a quantidade de grupos fosfinas sobre o suporte, assim como levou a um significativo aumento na carga de metal. A reação de hidroformilação de produtos naturais foi possível e, com o composto estragol, conversões de 100% foram alcançadas em 6 horas, com seletividade de 70% para aldeídos. Mesmo com evidências que sugerem a formação de espécies ativas moleculares, o suporte modificado possibilitou que o catalisador mantivesse sua atividade e seletividade por pelo menos seis reações sucessivas. Os materiais desenvolvidos apresentaram estabilidade quando manuseados ao ar, sem prejudicar sua vida útil e fácil separação. / The importance of catalysis to society may be seen in numbers: 90% of chemical production processes and more than 20% of all industrial products sold in the world use one or more catalytic steps. Thus, the development of efficient, active, and selective catalysts is crucial for creating cleaner and sustainable technologies. In addition, chemical reactions that generate new C-C bonds are among the most important transformations in organic chemistry and are the basis of this work. Rhodium catalysts presented herein are part of a careful investigation, which included the development, synthesis and characterization of metal nanoparticles and magnetic functional supports for use in the transformation of various molecules. The initial study of supported rhodium nanoparticles in cyclohexene hydrogenation reactions has driven our understanding of the behavior of these nanostructures, and the influence that different ligands and stabilizers may have in a well-known catalytic application. The identification of a highly active and recyclable catalytic system aroused our interest for its improvement for application in hydroformylation reactions. Prior to the synthesis of supported catalysts, studies with non-supported nanoparticles revealed that a modified system with the addition of phosphines was required for activation of the catalyst and the stabilizer used affected the catalytic activity. Thus, to enable efficient immobilization of the active species, the surface of the magnetic support was modified with methyldiphenylphosphine. The catalyst preparation removed, at least partially, the stabilizer adsorbed on the nanoparticles surfaces. The phosphine-functionalized support anchored the active species and avoided their leaching, allowing the reuse of the catalyst. The hydroformylation reaction of oct-1-ene reached 96% of conversion and 82% of selectivity to aldehydes, in 6 hours at 80°C. The metal loading of the catalyst was only 0.2%. Seeking to increase the efficiency in metal immobilization step and a better catalytic activity that would enable the use of more complex substrates, the magnetic support was modified with a hyperbranched polymer, which allowed an increase in the amount of external phosphines, as well as a significant increase in metal loading on the support. The hydroformylation reaction of natural products was possible and, with the estragole compound, 100% of conversion was achieved in 6 hours with 70% of selectivity to aldehydes. Despite evidence that suggests the formation of active molecular species, the modified support has enabled the catalyst to retain its activity and selectivity for at least six successive reactions. The materials developed could be handled in air without damaging their catalytic activity, durability and separation properties.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Includes bibliographical references. / Ph.D.

This thesis details the development and exploration of a catalytic carbonyl-olefin metathesis reaction. A catalytic transformation of this type has not been accomplished previously and stoichiometric processes were neither general nor desirable. A simple hydrazine catalyst was found to effect this reaction with the use of strained olefins. The development and optimization of this reaction, including the hydrazine catalyst, conditions and substrates, is discussed. Computational studies of the reaction mechanism are included. A stepwise process in which less strained olefins can undergo the reaction is also explored. Lastly, some initial explorations of transition metal complexes as catalysts for a carbonyl-olefin metathesis reaction are discussed, as well. In the second portion of this thesis, the use of cyclopropenimines as achiral organic superbases will be detailed. Previously, the Lambert group has developed this class of compounds as viable catalysts for asymmetric Michael and Mannich reactions. Cyclopropenimines are more basic than other commonly used organic bases, and therefore, can activate less acidic substrates. A simple, achiral cyclopropenimine was developed for use in base catalyzed or mediated processes. Several reactions have been explored as a comparison of cyclopropenimines to other commonly used bases.

<p>This thesis contains seven papers dealing with iridium and ruthenium based catalytic asymmetric reductions, either of ketones into chiral alcohols, or olefins into chiral alkanes. The first part of the thesis describes how we have designed and evaluated new bicyclic ligands containing either <i>N</i>,<i>S</i> or <i>N</i>,<i>N</i> chelating atoms. The ligands have been evaluated in the asymmetric Ir-catalyzed transfer hydrogenation of acetophenone. The complexes evaluated induced good enentioselectivity of the product. Moreover we have also utilized a commercially available chiral diamine (QCD-amine) as a ligand in the Ru-catalyzed hydrogenation of prochiral ketones, with excellent enantioselectivity for some of the substrates used. As part of this work we investigated, both theoretically and experimentally, the mechanism of this hydrogenation. Based on these results we have proposed a new reaction mechanism for this type of hydrogenations which involves active participation of the solvent in the catalytic cycle. The last part of the thesis describes the design, synthesis and evaluation of <i>N</i>,<i>P</i> and <i>N</i>₂<i>C</i>-carbene,<i>N</i> ligands for the Ir-catalyzed hydrogenation of carbon-carbon double bonds. The selectivities obtained in these investigations are among the best reported so far for a broad variation of substrates. A selectivity model for this hydrogenation has been derived and used in the rationalization of the results. As a part of this work we have synthesized and evaluated a new class of substrates, vinyl silanes, and showed that the scope of the hydrogenation reaction can be expanded to this new substrate class.</p>

No description available.

This thesis contains seven papers dealing with iridium and ruthenium based catalytic asymmetric reductions, either of ketones into chiral alcohols, or olefins into chiral alkanes. The first part of the thesis describes how we have designed and evaluated new bicyclic ligands containing either N,S or N,N chelating atoms. The ligands have been evaluated in the asymmetric Ir-catalyzed transfer hydrogenation of acetophenone. The complexes evaluated induced good enentioselectivity of the product. Moreover we have also utilized a commercially available chiral diamine (QCD-amine) as a ligand in the Ru-catalyzed hydrogenation of prochiral ketones, with excellent enantioselectivity for some of the substrates used. As part of this work we investigated, both theoretically and experimentally, the mechanism of this hydrogenation. Based on these results we have proposed a new reaction mechanism for this type of hydrogenations which involves active participation of the solvent in the catalytic cycle. The last part of the thesis describes the design, synthesis and evaluation of N,P and N2C-carbene,N ligands for the Ir-catalyzed hydrogenation of carbon-carbon double bonds. The selectivities obtained in these investigations are among the best reported so far for a broad variation of substrates. A selectivity model for this hydrogenation has been derived and used in the rationalization of the results. As a part of this work we have synthesized and evaluated a new class of substrates, vinyl silanes, and showed that the scope of the hydrogenation reaction can be expanded to this new substrate class.

A synthetic approach to produce lysergic acid by virtue of an asymmetric ring opening (ARO) of symmetrical 3,6-disubstituted-7,10-hydroxymethyl bridgehead substituted oxabicycles is described. The use of a Rhodium(I)/JosiPhos(R,S) catalyst system to effect an ARO using an amine nucleophile furnishes an enantiopure tetrahydronapthalene intermediate with the amine conveniently installed at the 6 position as in lysergic acid, with appropriate stereochemistry; further which, two subsequent annulations are necessary to form the fused 3,5-substituted indole and tetrahydropyridine to complete the synthesis. Progress of this work is described herein along with future directions. The second chapter in this thesis describes the modular and stereoselective synthesis of tetrasubstituted helical alkenes via a palladium-catalyzed domino reaction under Catellani conditions. These helical alkenes possess potentially interesting photochemical properties as molecular motors / switches, and can be applicable in the materials sciences as molecular machines.

A synthetic approach to produce lysergic acid by virtue of an asymmetric ring opening (ARO) of symmetrical 3,6-disubstituted-7,10-hydroxymethyl bridgehead substituted oxabicycles is described. The use of a Rhodium(I)/JosiPhos(R,S) catalyst system to effect an ARO using an amine nucleophile furnishes an enantiopure tetrahydronapthalene intermediate with the amine conveniently installed at the 6 position as in lysergic acid, with appropriate stereochemistry; further which, two subsequent annulations are necessary to form the fused 3,5-substituted indole and tetrahydropyridine to complete the synthesis. Progress of this work is described herein along with future directions. The second chapter in this thesis describes the modular and stereoselective synthesis of tetrasubstituted helical alkenes via a palladium-catalyzed domino reaction under Catellani conditions. These helical alkenes possess potentially interesting photochemical properties as molecular motors / switches, and can be applicable in the materials sciences as molecular machines.