Thesis (M.C.S.)--Regent College, 1986. / Abstract. Vita. Includes bibliographical references (leaves 178-185).

Thesis (M.C.S.)--Regent College, 1986. / Abstract. Vita. Includes bibliographical references (leaves 178-185).

La synthèse de produits complexes se doit de prendre en compte de nouvelles méthodes desynthèse plus efficaces, dont la fonctionnalisation de liaisons carbone-hydrogène. Dans cecontexte, la catalyse homogène par les métaux de transition s’est avérée performante, tout encontrôlant la régio- et la chimiosélectivité de la réaction. Les travaux de thèse présentés dansce manuscrit témoignent de l’efficacité de cette stratégie pour la construction rapide decomplexité moléculaire.Dans un premier temps, nous nous sommes intéressés à l’utilisation de précurseurs chlorés, cequi a permis d’étendre significativement le champ d’application de l’arylation C(sp3)-Hintramoléculaire pallado-catalysée. Ces travaux ont conduit à la synthèse de nombreuxhétérocycles, difficilement accessibles par d’autres voies de synthèse plus traditionnelles.Dans un deuxième temps, le développement d’une méthodologie de double arylation C-Hnous a permis de synthétiser des molécules polycycliques aux squelettes originaux. Une seuleet même espèce catalytique permet dans ce cas de réaliser les deux opérations d’activation CHavec succès.Par la suite, nous avons montré qu’il était possible de synthétiser des composés énantioenrichispar arylation C(sp3)-H intramoléculaire asymétrique. Pour cela, les ligands chiraux detype phosphépine se sont avérés particulièrement performants, et induisent desénantiosélectivités prometteuses.Enfin, notre attention s’est portée vers la synthèse de polycycles par arylation C(sp3)-Hintramoléculaire deshydrogénante. Les résultats encourageants obtenus apparaissent commeune preuve de concept dans ce domaine, où très peu de travaux de recherche ont été rapportés. / The direct functionalization of C-H bonds constitutes a faster and more « atom-economical »synthetic approach. This concept is gradually modifying organic chemistry, because itprovides chemists of both academic and industrial worlds with new disconnection strategies,giving access to molecules of original structures and properties in a more efficient andecological manner.In this context, we first investigated the extension of the intramolecular palladium-catalyzedC(sp3)-H arylation, by using aryl chlorides as coupling partners. This methodology wasapplied to the synthesis of fused valuable five-membered carbocycles and heterocycles.A further part of this work focused on the synthesis of polycyclic molecules by double C-Harylations. Interestingly, a single batch of catalyst was able to perform both operations in onepot, which indicates that this concept can be used for the rapid construction of molecularcomplexity.Then, we focused our efforts on the enantioselective synthesis of indanes and heterocyclicanalogues by intramolecular C(sp3)-H arylation. The employment of a chiral binepine ligandplays a key role in this palladium-catalyzed process to achieve moderate to highstereoinduction.Finally, our work was devoted to the construction of fused thiophenes by intramolecular PdIIcatalyzeddeshydrogenative C(sp3)–H arylation.

Le radiomarquage de molécules d’intérêt avec des isotopes radioactifs est d'un grand intérêt pour la communauté scientifique, car il influe fortement sur le processus de découverte dans les sciences de la vie et en médecine nucléaire. Les molécules radiomarquées ont été largement utilisées pour évaluer les réactions biochimiques, pour mesurer la distribution in vivo d'une substance ou pour réaliser des tests RIA (RadioImmunoAssay). En médecine nucléaire, des radiopharmaceutiques pour la thérapie par ra-dio-isotopes (RIT) et des radiotraceurs pour des expériences d'imagerie telles que la TEP (tomographie par émission de positons), la tomographie par émission monophotonique (TEMP) ou la scintigraphie ont été décrites. Plusieurs isotopes de l'iode peuvent être utilisés à la fois pour le diagnostic et le traite-ment : 123I pour l'imagerie TEMP, 124I pour la TEP, 125I pour l'analyse biologique et 131I pour la radio-thérapie et la scintigraphie.Les méthodes classiques de radio-iodation reposent sur l'utilisation d'un précurseur pré-fonctionna-lisé, qui doit être synthétisé, isolé et purifié avant d'être introduit à l'étape de radio-iodation. La méthode par radioiododéstannylation est la méthode la plus populaire, bien que les précurseurs stannylés soient connus pour leur synthèse difficile et leur toxicité. Le développement de nouvelles méthodes de radio-iodation représente donc un grand intérêt dans le domaine de la radiochimie.Sur la base de travaux antérieurs, notre groupe a mis au point une méthode de radio-iodation de N-acylsulfonamides au moyen d’une radio-iodation C-H médiée par le palladium à température ambiante. Cette stratégie originale permet le radiomarquage de molécules d’intérêt dans des conditions très douces sans utiliser de précurseurs chimiques.Sur la base de la littérature, notre groupe développe actuellement une nouvelle méthode de radio-iodation de dérivés d’arylsilanes par radioiododésilylation dans des conditions douces. Cette méthodo-logie générale permet pour le moment le radiomarquage de dérivés d'arylsilanes activés en conditions douces. / Labeling of (bio)molecules with radioactive isotopes is of high interest to for the scientific commu-nity, as it strongly impacts the discovery process in life science and nuclear medicine. Radiolabeled molecules have been extensively used to assess biochemical reactions, to measure in vivo distribution of a substance or to preform RIA (RadioImmunoAssay). In nuclear medicine, radio-therapeutics for RIT (RadioIsotope Therapy) and radio-tracers for molecular imaging experiments such as PET (Positron Emission Tomography), SPECT (Single Photon Emission Computed Tomography) or scintigraphy have been described. Several useful isotopes of iodine can be used for both diagnosis and therapy: 123I for SPECT imaging, 124I for PET imaging, 125I for biological assays and 131I for radio-therapy and scintig-raphy.Classical methods of radioiodination methods use a prefunctionalized precursor, which must be syn-thesized, isolated and purified before being introduced to the radio-iodination step. The radioiodode-stannylation method is the most popular method, although stannylated precursors are known for their difficult synthesis and their toxicity. The development of new methods of radioiodination is therefore of great interest in the field of radiochemistry.Based on a previous work, our group has developed a method to radio-iodinate N-acylsulfonamides through a room temperature palladium mediated C-H radio-iodination. This original strategy allows radiolabeling of biomolecules in very mild conditions without the use of chemical precursors.Based on literature, our group is now developping a new method to radio-iodinate arylsilyl derivates through radioiododesilylation in mild conditions. This general methodology allows for the moment the radiolabeling of activated arylsilyl derivates in mild conditions.

This dissertation involves inorganic/organometallic catalysis models, in particular the functionalization of carbon-hydrogen and carbon-carbon bonds. Computational methods have been utilized to better understand the factors affecting the kinetics and thermodynamics of C−H and C−C bond activation/functionalization in this dissertation. Chapter 2 investigates methane C−H activation with a diiminopyridine nitride/nitridyl complex of 3d transition metals and main group elements via three competing pathways: 1,2-addition/[2 + 2] addition, insertion and H-atom abstraction/proton coupled electron transfer. Chapter 3 investigates a transition metal catalyzed C=C bond functionalization involving C−N bond formations to synthesize aziridines from aromatic and aliphatic alkenes. The study focuses on anionic 3d transition metal (M = Mn, Fe, Co and Ni) triphenylamide-amine complexes with nitrene active intermediates for the aziridination reactions. Chapter 4 investigates a disphenoidal Ni(II) azido complex participating in intramolecular C−H functionalization and amination via a putative Ni nitridyl intermediate and a 1,2-addition/[2 + 2] addition pathway. In Chapter 5, methane oxidative addition to the Cp*ML (Cp* = η5-C5Me5; M = Co, Rh, Ir , L = CO, PMe3) motif is compared and contrasted when the classic CO and PMe3 ligands are replaced with the cyclic alkyl(amino) carbene (CAAC) as ancillary ligands.

Thesis (D. Min.)--Gordon-Conwell Theological Seminary, 2005. / Abstract and vita. Includes bibliographical references (leaves 264-276).

Thesis (D. Min.)--Gordon-Conwell Theological Seminary, 2005. / Abstract and vita. Includes bibliographical references (leaves 264-276).

Nitrogen is a vital element for the existence of life, as shown by its frequent presence in essential biomolecules, and inclusion into valuable drugs. Sulfonamides and their heterocycle counterpart, sultams, are N-containing functional groups and metabolically stable amide isosteres. Sulfa drugs, which contain these moieties, have a broad spectrum of medical applications. The industrial value of sultams has prompted the development of novel methods for their synthesis, and metal-catalyzed C-H amination reactions with nitrene precursors have recently shown promise. The current thesis presents a survey of conditions for benzo[d]sultam synthesis via intramolecular C-H amination of N-acyloxysulfonamides. Initially, using Ru(Bpy)3(PF6)2 as a photocatalyst and Et3N as a base enabled benzo[d]sultam formation by tertiary C-H amidation. The photoredox conditions were optimized to accommodate other 2,6-disubstituted-N-acyloxysulfonamides upon omission of the base, which consistently gave sulfonamide byproducts. Control reactions indicated that a thermal base-induced reaction was simultaneously occurring, both enabling productive C-H amidation and byproduct formation. Systematic optimization of base-induced conditions enabled sultam synthesis from 2,6-dialkyl- and tertiary ortho-monoalkyl-precursors in moderate yield, but sulfonamide formation still impeded the reaction.   An additional control reaction indicated that a thermal Ruthenium-catalyzed C-H amidation reaction was possible. Indeed, heating N-acyloxysulfonamides in the presence of Ru(Bpy)3(PF6)2 and in the absence of light and base enabled efficient C-H amidation, particularly with DCE as a solvent. A representative scope of 12 benzo[d]sultams was then synthesized including entries derived from ortho-monoalkyl-N-acyloxyarylsulfonamides. Aside from optimizing an efficient reaction for the synthesis of benzo[d]sultams through the cyclization of N-acyloxyarylsulfonamides, including the challenging primary C-H amidation of orthomonomethyl-substrates, the unique reaction conditions developed in this thesis set precedent for future investigation of hydroxylamine derived nitrene precursors. The optimization and design of superior ruthenium catalysts could allow for more challenging C-H amination reactions with hydroxysulfonamide derivatives and similar N-oxy nitrene precursors.

Significant developments have been made in the field of C–H activation. However, various disadvantages, mainly low reactivity and selectivity, limit their usage in large-scale synthesis. It is crucial to understand the mechanisms and the nature of the transient species involved in the C–H activation paths to develop effective catalytic routes for homogeneous C–H functionalization reactions. Computational techniques are employed in this study to throw light on these processes. Chapter 1 briefly introduces C–H activation and functionalization reactions. After classifying the reactions on the basis of mechanisms, computational studies on the mechanisms of C–H activation reactions are described. The challenges involved in the discovery of efficient homogeneous C–H functionalization catalysts and progress made in the field are discussed. The insights provided to overcome the problems associated with the catalytic C–H functionalization reactions in a few examples are highlighted. In Chapter 2, DFT model studies are carried out to estimate the affinity and selectivity of 16-electron half-sandwich d6-metal fragments (η5–C5H5)Re(CO)2 and (η6–C6H6)W(CO)2 for binding with alkane C–H bonds. Different C–H binding sites of pentane, at the M06 level of theory have been evaluated. The effects of ancillary ligand variations on the metal–pentane binding strength are studied by substituting different ligands such as N-heterocyclic carbene (NHC), PF3 and NO+ for one of the carbonyl ligands. Isomers of the metal-pentane C–H σ-complexes studied in this chapter are shown in Scheme 1. Binding energies of the terminal methyl C–H bonds (C1 and C5) are significantly lower than those of the methylene C–H bonds (C2, C3 and C4) in all the cases. The metal–pentane binding interactions of the rhenium complexes are significantly stronger than those of the corresponding tungsten analogs. The PF3 complexes have slightly greater binding energies compared to the CO complexes, in both Re(I) and W(0) analogs. These results are in conformity with the experimental results. The electron-deficient nitrosyl complexes have the highest binding energies. These results illustrate that by proper tuning of the electronic factors of the transition-metal fragments with different ancillary ligands, the alkane C–H binding affinity can be controlled. Energy decomposition analyses (EDA) are carried out to determine the nature of the interaction between the metal fragments and pentane C–H bonds. Scheme 1. Formation of pentane C–H σ-complexes Chapter 3 addresses the energetics of various intramolecular site-exchange (chain walking) processes and C–H oxidative addition reactions (Scheme 2) of the pentane C–H σ-complexes studied in Chapter 2. Four possible site-exchange processes such as 1,2-, 1,3-, 1,4- and 1,5-migration processes are studied using DFT/M06 level of theory. η2-(H,H)···M type transition states are located for these migrations (Scheme 2). The 1,3-migration is the most favorable process. Two different pentyl hydride isomers, as shown in Scheme 2, are obtained for oxidative addition of methyl and methylene C–H bonds of pentane for all systems, at same level of theory. Oxidative insertion of metal into the methyl C–H bonds is more favorable than insertion into the methylene C–H bonds for all complexes. The activation energies of all site-exchange and C–H oxidative addition processes of the Re(I) complexes are significantly greater than those of the corresponding W(0) complexes. For all these processes, the activation barriers of the electron-deficient NO+ complexes are the greatest among all ligand systems studied, in both Re(I) and W(0) systems. These results are consistent with the experimental results and suggest that the experimentally observed pentyl hydride isomer [(η5–C5H5)Re(CO)(PF3)H(C5H11)] might be Isomer B and not Isomer A (Scheme 2). The C–H oxidative addition reactions are less favorable than dynamic site-exchange processes in all complexes. These results imply that the metal fragments migrate along the pentane chain more easily than insert into the pentane C–H bonds. Scheme 2. Alkane chain walking and C–H oxidative addition reactions Chapter 4 deals with the mechanisms and energetics of a unique metal migration process of an olefin complex that proceeds via olefinic (C–H)···Metal interaction. Migration of the Re(I) fragment from one π face of the olefin to the opposite π face in [(η5–C5H5)Re(NO)(PPh3)(PhCH═CH2)]+ has been documented experimentally by Gladysz and coworkers. The experimental results provide evidences for an intramolecular mechanism for this process (i.e., without styrene dissociation from Re(I)) and based on kinetic isotope effects (KIE), the involvement of a trans C–H bond is indicated. Either oxidative addition or a vinylic (C–H)···Re interaction could account for the experimentally observed kinetic isotope effect. In this study, the free energy of activation for the migration of Re from one enantioface of the olefin to the other through various pathways is computed using DFT calculations at the B3LYP and M06 levels. Two pathways, one that involves migration of Re through a trans (C–H)···Re interaction and another that involves oxidative addition of Re into the trans C–H bond, are identified as possible paths (Scheme 3) at the B3LYP level. Surprisingly, at the M06 level, DFT computes a lower energy path for the conducted tour mechanism that is not consistent with the experimental KIE. But the computed energy profiles for the reaction are consistent with the experiment when computations are carried out at the B3LYP level. Scheme 3. Mechanisms of olefin π face exchange reaction In Chapter 5, the mechanistic studies of C–H metathesis of d6 half-sandwich complex [(η5–C5Me5)Ru(CH3)(CO)(C6H6)] are discussed. A 1-step mechanism that proceeds via a four-center transition state and a 2-step Oxidative Addition and Reductive Coupling mechanism (OA/RC) are identified as possible mechanisms (Scheme 4) using DFT/M06 level of theory. The 1-step mechanism is more favorable than the 2-step mechanism. As in the oxidative addition intermediate, metal–hydrogen bond is observed in the four-center transition state of the 1-step mechanism. This mechanism is referred to as Oxidative Hydrogen Migration (OHM) rather than σ-Bond Metathesis (σ-BM) which proceeds via a transition state without M−H bonding. The effects of metal (M = Fe(II), Ru(II) or Os(II)) and ancillary ligand (L = H–, NHC, CO or NO+) variations on the mechanisms and energetics of the model Cp complex [(η5–C5H5)M(CH3)(L)(C6H6)] are also studied (Scheme 4). Scheme 4. Oxidative hydrogen migration vs Oxidative addition/reductive coupling Increase in the electron-density on the metal center, using electron-donating ligands such as H−, favors the formation of the oxidative species (intermediate or transition state) and reduces the activation barriers of the C–H metathesis reaction. Similarly, the electron-withdrawing NO+ ligand, which reduces the electron density on the metal center, increases the activation energies of the C–H metathesis reaction or disfavors the formation of the oxidative species. Factor affecting the choice of the mechanism of the C–H metathesis reaction is found to be the net charge transfer between the two fragments [(η5–C5H5)M(CH3)(L)] and benzene in [(η5–C5H5)M(CH3)(L)(C6H6)]. The computational studies reported in this thesis provide valuable insight into the mechanisms and energetics of C–H binding, activation and fluxional processes of the (C–H)···Metal σ alkane and alkene complexes. These studies will be helpful in solving problems associated with the C–H activation reactions. Reference Thenraj, M.; Samuelson, A. G. Organometallics 2013, 32, 7141. (For structural formula and figures pl see the abstract pdf file.)

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