Thesis (Ph.D.)--Mississippi State University. Department of Chemistry. / Title from title screen. Includes bibliographical references.

Title from first page of PDF document. Includes bibliographical references (p. 154-156).

Une des voies privilégiées pour réduire la teneur en soufre dans les essences commerciales est l'hydrodésulfuration sélective (HDS) des essences issues du procédé de FCC. Une essence étant composée d'un mélange de composés soufrés (1000 ppm) et d'oléfines (20-40%pds). Il est important de comprendre leur transformation de manière à améliorer l'HDS tout en minimisant l'hydrogénation (HYD) des oléfines. Par conséquent, la transformation de plusieurs molécules modèles soufrées (2-méthylthiophène, 3-méthylthiophène et le benzothiophène) et oléfiniques (hex-1-ène, 4-méthylpent-1-ène, 3,3-diméthylbut-1-ène et 2,3-diméthylbut-2-ène) a été étudiée dans les conditions opératoires d'HDS. Par une approche expérimentale couplée à de la modélisation cinétique, nous avons établi une échelle de réactivité entre les composés soufrés d'une part et les oléfines d'autre part. Le benzothiophène est le composé le plus réactif, mais aussi celui qui est le plus inhibiteur pour la transformation des autres composés soufrés. Concernant les oléfines, l'hex-1-ène est la plus réactive par rapport aux autres oléfines ramifiées. Lorsque ces composés sont en mélange, on constate des inhibitions mutuelles plus au moins conséquentes selon la structure des composés modèles. Ces effets qui résultent de compétitions à l'adsorption entre les molécules à la surface du catalyseur ont été modélisés et quantifiés (constantes cinétique et d'adsorption) à partir d'un modèle unique en considérant le formalisme de Langmuir-Hinshelwood. / A preferred route to reduce the sulfur content on the commercial gasoline is the selective hydrodesulfurization (HDS) process of FCC gasoline. A typical gasoline is composed by a mixture of sulfur (1000 ppm) and olefins (20-40%wt) compounds. Therefore, it is important to understand their transformation in order to improve the HDS and minimizing the olefin hydrogenation (HYD). Consequently, the transformation of various sulfur (2-methylthiophene, 3-methylthiophene and benzothiophene) and olefins (hex-1-ene, 4-methylpent-1-ene, 3,3-dimethylbut-1-ene and 2,3-dimethylbut-2-ene) has been studied under HDS operating conditions.By experimental and theoretical (kinetic modeling) approaches, a reactivity scale has been established between the sulfur compounds on one hand and olefins compounds on the other hand. The benzothiophene is the most reactive compound. However it is the most inhibitor compound for the transformation of others sulfur compounds. Regarding the olefins, the hex-1-ene is the most reactive compound among the others branched compounds. A mutual inhibition has been observed when those compounds are studied in mixture according with their structures. These effects result from competitive adsorption between the molecules on the catalyst surface. These results could be modeled and quantified (adsorption and kinetic constants) from a unique model considering the Langmuir-Hinshelwood formalism.

Cette thèse décrit le développement de nouvelles réactions de difonctionnalisation catalytique d’oléfines impliquant des transferts de nitrène médiés par des complexes de dirhodium(II).La première partie de ce manuscrit s’articule autour de la réactivité d’alcènes riches en électrons, c’est-à-dire substitués par un hétéroatome. L’application des conditions de transfert de nitrène catalytiques a permis la fonctionnalisation oxydante des positions C2 et C3 de l’indole. En utilisant cette stratégie, il est donc possible d’effectuer formellement des réactions d’oxyamination intermoléculaire et de diamination intramoléculaire. Dans ce dernier cas, le motif indoline formé étant présent dans certains produits naturels, la synthèse totale de la Pestalazine B a pu être initiée. Le champ d’application de ces réactions a été étendu aux énamides en collaboration avec le groupe du Professeur Isabelle Gillaizeau.La seconde partie de ce travail concerne le développement de la réaction d’oxyamination d’oléfines aromatiques et aliphatiques. Le champ d’application de cette réaction a été étudié en détail tandis que des expériences témoins et des analyses RMN ont permis de proposer un mécanisme original.Enfin, dans un dernier temps, nous avons démontré que par extension du concept, l’application des transferts de nitrène catalytiques permet de réaliser des réactions de diamination intermoléculaire d’oléfines. / This manuscript describes the development of new reactions for the difunctionalization of alkenes that involve dirhodium(II)-catalyzed nitrene transfers.The first part of the studies focuses on the reactivity of electron-rich alkenes, i.e. substituted by a heteroatom. The application of catalytic nitrene transfers has led to the development of oxidative conditions for the difunctionalization of the 2,3-π-bond of indolic derivatives. The strategy, thus, has allowed to perform formal reactions of intermolecular oxyamination and intramolecular diamination. The latter gives access to indoline skeleton found in the structure of several natural products such as Pestalazine B, the total synthesis of which has been initiated. The scope of intermolecular oxyamination has then been extended successfully to enamides in collaboration with the group of Professor Isabelle Gillaizeau.The second part of the experimental work has been aimed at applying the catalytic oxyamination to aromatic and aliphatic alkenes. The scope of the reaction has been extensively studied while test experiments and NMR analysis have allowed to propose an unexpected mechanism based on the Lewis acid character of the metallanitrene.Finally, the scope of catalytic nitrene transfers has been extended to the intermolecular diamination of alkenes with the development of bis(arenesulfonyl)imide-type reagents.

Unspecific peroxygenase (EC 1.11.2.1) represents a group of secreted hemethiolate proteins that are capable of catalyzing the selective mono-oxygenation of diverse organic compounds using only H2O2 as a cosubstrate. In this study, the peroxygenase from Agrocybe aegerita (AaeUPO) was found to catalyze the hydroxylation of various linear (e.g n-hexane), branched (e.g. 2,3-dimethylbutane) and cyclic alkanes (e.g. cyclohexane). The size of n-alkane substrates converted by AaeUPO ranged from gaseous propane (C3) to n-hexadecane (C16). They were mono-hydroxylated mainly at the C2 and C3 position, rather than at the terminal carbon, and the corresponding ketones were formed as a result of overoxidation. In addition, a number of alkenes were epoxidized by AaeUPO, including linear terminal (e.g. 1-heptene), branched (2-methyl-2-butene) and cyclic alkenes (e.g. cyclopentene), as well as linear and cyclic dienes (buta-1,3-diene, cyclohexa-1,4-diene). Furthermore, the conversion of terminal alkynes (e.g. 1- octyne) gave the corresponding 1-alkyn-3-ol in low yield. Some of the reactions proceeded with complete regioselectivity and - in the case of linear alkanes, terminal linear alkenes and alkynes - with moderate to high stereoselectivity. The conversion of n-octane gave (R)-3-octanol with 99% enantiomeric excess (ee) and the preponderance of the (S)-enantiomer reached up to 72% ee of the epoxide product for the conversion of 1-heptene. Catalytic efficiencies (kcat/ Km) determined for the hydroxylation and respectively epoxidation of the model compounds cyclohexane and 2-methyl-2-butene were 2.0 × 103 M-1 s-1 and 2.5 × 105 M−1 s−1. The results obtained in the deuterium isotope effect experiment with semideuterated n-hexane and the radical clock experiment with norcarane clearly demonstrated that the hydroxylation of alkanes proceeds via hydrogen abstraction, the formation of a substrate radical and a subsequent oxygen rebound mechanism. Moreover, stopped-flow experiments and substrate kinetics proved the involvement of a porphyrin radical cation species (compound I; AaeUPO-I) as reactive intermediate in the catalytic cycle of AaeUPO, similar to other hemethiolate enzymes (e.g. cytochrome P450 monooxygenases, P450s). / Die Gruppe der Unspezifischen Peroxygenasen (EC 1.11.2.1) umfasst extrazelluläre Häm-Thiolat-Enzyme, die mittels H2O2 als Cosubstrat die selektive Monooxygenierung unterschiedlicher organischer Verbindungen katalysieren. In der vorliegenden Arbeit konnte gezeigt werden, dass die von Agrocybe aegerita sekretierte Peroxygenase (AaeUPO) verschiedene lineare (z. B. n-Hexan), verzweigte (z. B. 2,3-Dimethylbutan) und zyklische Alkane (z. B. Cyclohexan) hydroxyliert. Die Größe der von der AaeUPO umgesetzten Substrate reichte vom gasförmigen Propan (C3) bis hin zu n-Hexadekan (C16). Die Alkane wurden bevorzugt am zweiten und dritten Kohlenstoffatom (C2 und C3) hydroxyliert; eine Hydroxylierung am terminalen Kohlenstoff konnte nur vereinzelt und in geringem Umfang beobachtet werden. Die Überoxidationen der primär gebildeten, sekundären Alkohole führte außerdem zur Entstehung der entsprechenden Ketonderivate. Darüber hinaus wurde eine Vielzahl linearer terminaler (z. B. 1-Hepten), verzweigter (z. B. 2-Methyl-2-Buten) und zyklischer Alkene (z. B. Cyclopenten) sowie linearer und zyklischer Diene (1,3-Butadien, 1,4-Cyclohexadien) durch die AaeUPO epoxidiert. Die Umsetzung terminaler Alkine (z. B. 1-Octin) führte zur Entstehung der jeweiligen 1-Alkin-3-ole. Manche dieser Reaktionen verliefen ausgeprägt regioselektiv und, im Falle der linearen Alkane sowie der linearen terminalen Alkene und Alkine, mit mittlerer bis hoher Stereoselektivität. So ergab beispielsweise die Umsetzung von n-Octan einen Enantiomerenüberschuss größer 99% für (R)-3-Octanol; die Epoxidierung von 1-Hepten lieferte einen Enatiomeerenüberschuss (ee) von bis zu 72% für das (S)-Enantiomer. Die katalytischen Effizienzen, die für die Hydroxylierung bzw. Epoxidierung der Modellverbindungen Cyclohexan und 2-Methyl-2-Buten ermittelt wurden, betragen 2.0 × 103 M-1 s-1 und 2.5 × 105 M−1 s−1. Der ausgeprägte Deuterium-Isotopen-Effekt, der im Zuge der Umsetzung von semideuteriertem n-Hexan beobachtet wurde sowie die Ergebnisse des Radical-Clock-Experiments mit Norcarane als Substrat bestätigten, dass die Hydroxylierung von Alkanen über Wasserstoffabstraktion, die Bildung eines Substratradikals und anschließende direkte Sauerstoffrückbindung verläuft. Die Stopped-Flow-Experimente belegen zudem das Auftreten eines Porphyrin-Kationradikal-Intermediates (Compound I; AaeUPO-I) im katalytischen Zyklus der AaeUPO (vergleichbar mit dem reaktiven Intermediat der P450-Monooxygenasen).

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.

No description available.

There are two sections to this research dissertation. Part one includes syntheses of fused-ring heterocycles derived from thiazole, oxazole, benzoxazole and benzothiazole derivatives and trifluoroacetylations of in situ generated N-methyl cyclic ketene-N,O/Sacetals. Attempted functionalized polymer syntheses from plant-derived 5-(hydroxymethyl) furfural are discussed in part two. Three 2-methylthiazoles, 2,4,5-trimethyloxazole, 2-methylbenzoxazole and 2- methyl-benzothiazole were each reacted with benzoyl chloride in acetonitrile/triethylamine to generate benzyl-vinyl esters. Base hydrolysis of these benzyl-vinyl esters formed 2-(heterocyclic)-1-phenylethenols which exist in both ketoenol tautomeric forms. These tautomers were used as starting materials for fused-ring heterocycle syntheses. Each tautomeric pair react with dimethyl acetylenedicarboxylate in methanol giving the 5,6-ringused 8-benzoyl-5-oxo-5H-thiazolo-, 8-benzoyl-5-oxo-5H-oxazolo-, 4-benzoyl-1-oxo-1H-benzo[4,5]oxazolo- and 4-benzoyl-1-oxo-1H-benzo[4,5]thiazolo [3,2-a]pyridinecarboxylate derivatives. Two novel 5,7-ringused 9-benzoyl-2,3- dimethyl-5,6-dihydrothiazolo- and 9-benzoyl-2,3-dimethyl-5,6-dihydrooxazolo[3,2-a] azepine-5,6,7,8-tetracarboxylates formed when the tautomers formed from 2,4,5- trimethyl thiazole and 2,4,5-trimethyl oxazole were reacted with DMADC. These tautomers react with 1,3-diacid chlorides in acetonitrile/triethylamine affording the 5,6-ringused 8-benzoyl-6,6-dialkyl-6H-thiazolo- and 8-benzoyl-6,6- dimethy-6H-oxazolo-, 4-benzoyl-2,2-dimethyl-1H-benzo[4,5]thiazolo- and 4-benzoyl- 2,2-dimethyl-1H-benzo[4,5]oxazolo[3,2,-a]pyridinedione derivatives. Functionalized 5,6- ringused 8-benzoyl-6H-thiazolo- and 8-benzoyl-6H-oxazolo[3,2]pyrimidine-5,7- diones, and 4-benzoyl-1H-benzo[4,5]thiazolo- and 4-benzoyl-1H-benzo[4,5]oxazolo[3,2- c]pyrimidine-1,3(2H)-diones formed reacting the tautomers with N-chlorocarbonyl isocyanate in THF/triethylamine. Significant ring size and substituent effects were observed in trifluoroacetylations of in situ-generated cyclic ketene-N,O/S acetals. In situ-generated 3,4,4-trimethyl-2- methylene-oxazolidine, 3-methyl-2-methylene-oxazolidine and 3-methyl-2-methylene- 1,3-oxazinane each formed β,β-bistrifluoroacetylated products. However, 3-methyl-2- methylene-oxazolidine also afforded a γ-lactam by an iodide-catalyzed rearrangement of its β,β-bistrifluoroacetylated derivative. In situ-generated 3-methyl-2-methylenethiazolidine gave both β-mono- and β,β-bistrifluoroacetylation products. 5-(Hydroxymethyl)furfural synthesized from sucrose was converted to 2,5- bis(hydroxymethyl)furan (2,5-BHMF). 7-Oxanorbornene-type Diels-Alder adducts synthesized from 2,5-BHMF were used as monomers for both ring opening metathesis polymerizations (ROMPs) and polycondensations. ROMP, followed by polycondensation or vise versa were expected to give highly functionalized cross-linked polymers. ROMP of the monomers using three Grubbs’ 1st, 2nd and 3rd generation catalysts were unsuccessful due to the presence of hydroxymethyl groups at one or both bridgeheads that could coordinate Ruthenium. With one bridgehead methyl present ROMP proceeded. Low molecular weight polyesters were synthesized via polycondensation. One was crosslinked using ROMP, but not to its gel point.

No description available.

Aqueous-biphasic organometallic catalysis is, as illustrated by the industrial hydroformylation of propene and butene, one of the most promising ways to overcome the intrinsic problem of catalyst separation in organometallic catalysis. However, for poorly water-soluble substrates, mass transfer limitations bring the reaction rate below any that could be economically viable, greatly limiting the scope of this elegant technology. We have studied three different strategies to overcome this limitation. We developed additives that speed up the reaction whilst retaining fast phase separation and good metal retention. Evidence suggests that those additives affect the reaction by forming emulsions with poor stability under the reaction conditions These emulsions increase the interfacial surface area but break after settling for a short time. We also developed ligands that allow the catalyst to be reversibly transported between an aqueous and an organic phase upon addition and removal of carbon dioxide. This allows the reaction to be carried out under homogeneous conditions, only limited by intrinsic kinetics, and the catalyst to be separated by aqueous extraction triggered by carbon dioxide. The catalyst can be returned to a fresh organic phase by flushing out the carbon dioxide. By applying this methodology for the hydroformylation of medium chain length alkenes, very high reaction rates were obtained and the catalyst could be recycle three times with excellent retention of activity and low metal leaching. This methodology could also be reversed with the reaction being carried out in an aqueous phase in the presence of carbon dioxide and extracting the catalyst into an organic solvent using nitrogen flushing. Finally, we briefly investigated the use of an oscillatory baffled reactor as a mean for mass transfer improvement for aqueous-biphasic hydroformylation. This new type reactor did not improve the performance of the system under the investigated conditions, but may require less energy input for equivalent agitation and mixing.