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The prevalence of fluorine in natural products is scarce. There are but a handful of compounds that have been discovered to date. This could be largely attributable to the occurrence of fluorine in nature as fluoride (F-). — One might recognize such nomenclature from the ingredients list on a toothpaste tube — In fact, naturally occurring fluoride is most commonly found as fluorite (CaF2) or cryolite (Na3AlF6). As such, the introduction of fluorine via biological pathways has been limited to use of aqueous F- (a very poor nucleophile). This fact — coupled with its naturally low concentration in water — has created the ripe conditions for this shortage. In a way this has proven fertile for synthetic chemists because nature has not yet evolved a method for the deconstruction of partially or fully fluorinated compounds. Considering the above, as synthetic methodologies for the construction of carbon-fluorine bonds became available, so too did the discovery of their valuable properties. So beneficial are these properties that C-F bond-containing compounds have become commonplace in many households throughout the world. For example, practically every home relies on these compounds for use in their refrigerators. Other examples of useful fluorinated materials include blowing agents, non-stick coatings, pharmaceuticals, agrochemicals, liquid crystals, and lubricants. With all these applications and seemingly easy availability of these compounds, it is interesting to learn that original synthetic methods are still being employed today. As such, the objective of this Thesis is to develop ‘greener’ routes for the synthesis of fluorocarbons. We hypothesized that by studying transition metal-fluoroalkyl complex-mediated reactions, a more efficient catalytic system could be developed. A foreseen complication arises from the thermodynamic stability of C-F, transition metal-F and transition metal-CRF bonds. Improvements to overcome these caveats include the use of first-row late transition metal complexes. Presented herein are additions to this body of knowledge by expanding on the reactivity of nickel, copper and silver fluoroalkyl complexes. The approach applied in this work, in line with ‘green’ chemistry principles, was to source readily available fluorinated reagents, i.e. fluoroalkenes and fluoroarenes, to reduce the number of steps for the synthesis of new fluorinated compounds. Chapter 2 builds on the well-established oxidative cyclization of C2 fluoroalkenes to nickel (0), which yields new C4 units. The use of a bulky N-heterocyclic carbene ligand was found to enhance reactivity by reducing the coordination number at nickel. Examples of room temperature Cα-F and Ni-CF bond activation and functionalization reactions are presented. Chapters 3, 4 and 5 re-examine the insertion of fluoroalkenes into silver and copper fluorides and hydrides. Building on precedent of addition reactions to hexafluoropropene, this fluoroalkene was examined first. In so doing, a versatile and inexpensive copper heptafluoroisopropyl reagent was developed (Cu-F addition to (CF3)CF=CF2. With easy access to new heptafluoroisopropyl complexes, they were systemically studied for their applications in catalysis. This revealed key features, particularly the lability of the M-hfip bond, which could be detrimental to catalytic reactions. As such, a nickel complex-mediated carbonylative heptafluoroisopropylation reaction and copper complex-mediated nucleophilic addition to electrophiles were developed. When a copper hydride was used instead, the in situ generated fluoroalkyl [Cu-H addition to (CF3)CF=CF2] was susceptible to β-fluoride elimination. Chapter 4 expands this methodology to achieve the catalytic consecutive hydrodefluorination of fluoroalkenes, demonstrating the scope and limitations of this system. Furthermore, the critical role of the phosphine ligand in accessing an L3Cu-H addition and unusual β-fluoride elimination mechanism is highlighted. However, tetrafluoroethylene proved resistant to this reaction because the fluoroalkyl resting state of this alkene, Cu-CF2CF2H, is unusually robust. Chapter 5 investigates the utility of this fragment and others in C(sp2)-RF cross-coupling and nucleophilic substitutions. With focus on new routes for late stage fluorination and examples of nickel (0) complex-catalyzed selective C-F bond functionalization reactions, Chapter 5, continues studies for low-temperature and DMAP-assisted conditions for aryl-F cross-coupling reactions with boronic acid esters. Lastly, Chapter 6 reviews the advances presented in this Thesis, provides a link to the expected lasting impacts and attempts to provide guidance to future research on transition-metal complexes in the synthesis of C-F or C-RF containing compounds. Moreover, with the introduction of a new hydrodefluorination technology, previously scarce fluoroalkenes (e.g. 1,2-difluoroethylene) can now be used more freely, potentially leading to the development of new refrigerants or materials applications.

Sphingosine 1-phosphate (S1P) is a lipid chemoattractant molecule. Once formed, S1P can be transported extracellularly by S1P transporters spinster homolog 2 (Spns2) or major facilitator domain containing 2B (mfsd2b). In the extracellular space, S1P can bind to S1P-specific G-protein coupled receptors (S1PR), which initiate many signaling pathways. A critical role of extracellular S1P is its ability to cause lymphocyte egress, which can have implications for inflammatory and autoimmune diseases. For this reason, there has been a growing interest in exploring potential spns2 inhibitors to further elucidate their therapeutic potential. Initial screenings confirmed that fused heterocycles, including phthalimide and benzoxazoles, demonstrated moderate inhibition of Spns2 using a HeLa cell assay. An extensive structure-activity relationship (SAR) study of these scaffolds was performed to analyze the impact of various amine head groups, regioisomers, and alkyl tails on performance. It was determined that 2-aminobenzoxazoles with secondary amines were potent inhibitors of the transporter. Additionally, the position of the lipophilic tail moiety played a large role in activity. From these modifications, SLB1122168 (2.44p) was found to be our lead compound. It was determined that (2.44p) had an IC50 of 94 ± 6 nM and was shown to be efficacious in decreasing lymphocyte count by 55% in a dose-dependent manner in both rat and mice models. The discovery of (2.44p) can serve as a novel chemical tool to investigate Spns2 biology and use it as a probe to determine the potential of Spns2 as a drug target. Organoboron compounds are useful synthetic intermediates in forming C-X, C-C, and C-H bonds. One way to synthesize these compounds is through copper catalysis. Copper is favorable to other transition metals because it is an Earth-abundant, low-cost metal that can be utilized in regio- and stereoselective reactions. Conjugated 1,3-enynes are important functional groups that iii are found in active natural products, organic synthetic intermediates, and materials. Previous methods used rare transition metals, designer ligands, or harsh acidic conditions to synthesize such compounds. In this dissertation, we developed a stereoselective one-pot copper-catalyzed semi-reduction of 1,3-diynes to produce (Z)-1,3-enynes. This method uses Cu(OAc)2, HBpin and Xantphos to successfully synthesize (Z)-1,3-enynes that were tolerated well over a broad substrate scope, including heterocyclic, alkyl, and aryl substituents. It was determined that this reaction went through a 2-boryl intermediate which was facilitated by a CuH species. / Doctor of Philosophy / Autoimmune diseases are caused by immune cells attacking healthy cells. The signaling lipid sphingosine-1-phosphate (S1P) plays a major role in trafficking immune cells, in which immune cells follow the S1P gradient from low concentrations (secondary lymphoid tissues) to high concentrations (lymph). In the case of multiple sclerosis, immune cells can attack healthy neurons that cause a myriad of symptoms. Currently, there are four drugs approved by the Food and Drug Administration (FDA) targeting the S1P pathway for multiple sclerosis. In all cases, these drugs act as S1P-receptor (S1PR) functional antagonists, which decreases the amount of extracellular S1P, which in turn decreases the immune cells in the lymph that can attack healthy cells. Unfortunately, all four drugs exhibit on-target cardiovascular side effects. To circumvent the on-target side effects seen in current FDA-approved drugs, other nodes of the S1P pathway have been assessed for multiple sclerosis. One node of interest is spinster homolog 2 (Spns2), a transporter of S1P, whose inhibition has also been shown to decrease extracellular S1P. In this dissertation, we will be assessing various inhibitors for their in vitro and in vivo properties. 1,3-Enynes are a functional group found in medicinally relevant compounds and can be used as intermediates to make more complex compounds. Current methods to make this functional group use expensive rare metals or harsh acidic conditions. We developed new methods that utilized copper, an abundant metal, and boron, an atom whose empty p orbital allows for unique reactivity. Utilizing a copper-hydride species allowed us to semi-reduce 1,3-diynes to (Z)-1,3-enynes, where water was used instead of acid to allow for the semi-reduction to occur. This reaction was shown to tolerate a wide range of substrates and gave good to excellent yield.

Au cours de ce travail de recherche, nous nous sommes intéressés à la réaction d'hydrosilylation asymétrique de diverses cétones aromatiques catalysée par des complexes chiraux du cuivre. Un premier système catalytique mis au point à partir du fluorure de cuivre (II) et du ligand (S)-BINAP (1 mol %) a permis d'atteindre 92 % d'excès énantiomérique en alcools chiraux obtenus. L'aspect fondamental de ce procédé réside dans l'effet accélérateur de l'oxygène. Nous avons alors mis au point une méthode de réduction de diverses cétones aromatiques dans des conditions douces et à l'air. Un deuxième système catalytique, plus efficace en termes de réactivité et de sélectivité, mis au point à partir de fluorure de cuivre (I) et de ligands diphosphines chiraux a permis de réduire de façon catalytique et énantiosélective diverses cétones aromatiques. L'effet accélérateur de l'oxygène est nettement plus marqué comparé au système au fluorure de cuivre (II). L'optimisation est réalisée en présence de ligands encombrés de la famille de la MeO-BIPHEP. Une méthode de réduction de cétones aromatiques pratique, douce, efficace, sélective (jusqu'à 95 % e.e.) et avec des taux catalytiques particulièrement intéressants (< 0,05 mol %) est alors proposée. L'étude mécanistique entreprise nous a permis de préciser certaines étapes du cycle catalytique envisagé pour cette réaction et de souligner la complexité de la réaction étudiée. Mots-clés : catalyse asymétrique, hydrosilylation asymétrique, hydrure de cuivre, effet de l'oxygène, étude mécanistique. / During this research work, we have studied the asymmetric hydrosilylation reaction of various aromatic ketones catalysed by chiral copper complexes. The first system, based on copper fluoride (II) and (S)-BINAP as ligand (1 mol %), allowed us to achieve up to 92% e.e. in chiral alcohols. The fundamental aspect of this reaction is based on the accelerating effect of oxygen. A smooth method of various aromatic ketones was therefore established under air atmosphere. A second catalytic system, based on copper fluoride (I) and diphosphine ligands, was developed. This system was found to be more efficient in terms of reactivity and selectivity for the reduction of various aromatic ketones than the first system. An increase in sensitivity to the accelerating effect of the oxygen was observed with this copper (I) system. Some optimisations have shown than hindered ligands such as MeO-BIPEPH furnish up to 95% e.e. in the presence of a very low catalytic loading (< 0,05 mol %). Those conditions allowed the reduction of aromatic ketones in practical, soft, efficient and selective conditions. The mechanistic study enabled us to get a better understanding of the catalytic cycle but also pointed out the complexity of the reaction. Keywords: asymmetric catalysis, asymmetric hydrosilylation, copper hydride, oxygen effect, mechanistic investigation.

The synthesis of metal-redox active ligand complexes is described, along with reactivity studies aimed at facilitating novel C-N bond forming reactions. A copper bis(iminosemiquinone) structure is characterized, analyzed and its reduction series are characterized and the reactivity of the Cu(II) bis(amidophenolate) analog is investigated with tosyl azide. The identification of the major reaction product and its characterization is detailed, with reaction sensitivities and heavily distorted x-ray diffraction single crystal structure generating a complex data set. The characterization of the isolated product is ongoing, with EPR studies aimed at identifying the radical nature of the complex. Unusual solvent effects and solubility issues have been noted with these initial EPR studies and more data is necessary before analysis can be properly attempted. An ytterbium bis(amidophenolate) complex was synthesized and its reactivity studied with aryl azides. Initial reactivities generate the first documented lanthanide tetrazenes in-lieu of the targeted ytterbium imido. Reactivities and characterization of these complexes support a stable, heavily ionic tetrazene-metal complex with no observed redox nature, UV light sensitivities, or imido azide-tetrazene equilibrium observed in various tetrazene transition metal complexes. Synthesis of a sterically blocked ytterbium imido was attempted, utilizing DMAP. Initial isolation was achieved with characterization and reactivity studies supporting the imido nature of the complex. The weak coordinating of the DMAP provided instability that proved in opposition to crystallization, however, so the imido could not be confirmed. Initial reactions using alternative steric hinderance from triphenylphosphine oxide and pyridine N-oxide prove promising to increasing the stability of the presumed ytterbium imido. Organic synthesis was performed generating a potential antibacterial agent. The synthesis of cyclopropenes was initiated as antagonists for ETR proteins in fruits and plants. The intermediates proved highly sensitive to harsh chemical conditions, which was overcome utilizing a tin-mediated Barbier allylation. The cyclopropene alcohol synthon was synthesized, though protecting group optimization is necessary.

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