Thesis advisor: Jeffery A. Byers / This dissertation discusses the development of iron-based catalysts for Suzuki-Miyaura cross-coupling reactions and some of the unique reactivity that was discovered as a direct result of these studies. Chapter one will review the area of iron-catalyzed cross-coupling with an emphasis placed on areas where iron provides complimentary reactivity to other metals. Chapter two will detail the initial discovery of conditions that allow for iron-catalysts to participate in the cross-coupling of aryl boronic esters and alkyl halides. Chapter three will discuss the the development of ligands for iron that allow for more general cross-coupling reactivity to be observed. Finally, chapter four will discuss the unique C-H funtionalization reactivty that has been observed as byproducts in chapters two and three. Digging deeper into this reactivty lead to the discovery of a completely novel three-component coupling reaction mediated by the iron complexes discovered in chapter three. / Thesis (PhD) — Boston College, 2020. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

>Magister Scientiae - MSc / Due to the negative impact on the environment and the associated biological risks on human and animal life, the need for eco-friendly synthetic protocols is critical. With the rapid advancement in nanotechnology, this extends to the synthesis of nanomaterials. Eco-friendly nanoparticle synthesis protocols have led to the use of fungi, plants and other biological substances, due to their remarkable ability in reducing metal ions. This led to the formation of very efficient hybrid catalysts, which are partially organic/inorganic composites. Palladium nanoparticles have drawn much interest due to its potential in catalytic applications and in photovoltaic cell development. In this study, the brown marine algae, Ecklonia radiata, was employed as a putative palladium nanoparticle bioreactor. Aqueous extracts of the algae were used as a supporting matrix for the synthesis of palladium nanoparticle (AE-PdNPs) catalysts according to the principles of green chemistry. The catalysts were then assessed for their capability in various carbon-carbon coupling reactions such as Suzuki-Miyaura, Sonogashira, and Heck coupling reactions. Selectivity studies were also performed. The PdNPs were compared to “model” polyvinylpyrrolidone palladium nanoparticles (PVP-PdNPs), synthesized according to literature methods. A variety of spectroscopic techniques were used to characterize the nanoparticles and the organic reaction products, including HRTEM, EDX, NMR, FTIR, DLS, TGA, UV-Vis, ICP-AES, GC-MS and XRD spectroscopy. qNMR was used to determine the product % yields. The aqueous extracts were characterised using NMR and a variety of assays, including total antioxidant potential, total reducing power and radical scavenging ability) to assess its ability to reduce the Pd metal salt. 2D NMR revealed polysaccharides and polyphenols to be the major and minor components, respectively, present in the extract. HRTEM images revealed the average size of the AE-PdNPs and PVP-PdNPs to be 12 nm and 8 nm, respectively. The images also showed the shapes of the NPs to be cubic for the AE-PdNPs and cubic or triangular for the PVP-PdNPs. SAED and XRD spectroscopy revealed the face-centred cubic phase and polycrystalline nature of the AE-PdNPs. No reliable data, other than the HRTEM images was obtained for the PVP-PdNPs. Zeta potential and DLS measurements confirmed the negative charge present on the surface of the nanoparticles, while the hydrodynamic radii were found to be 65 nm and 99 nm for the AE- and PVP-PdNPs, respectively, substantiating the presence of the capping agents. ICP-AES analysis revealed the Pd content of the NPs to be 48.8 and 28.9 ppm for the AE- and PVP-PdNPs. Following characterization, the PdNPs were assessed as potential catalysts in the Suzuki-Miyaura, Heck and Sonogashira carbon-carbon coupling reactions. Bromo and iodo substrates were employed, together with sterically hindered substrates, with a nitro moiety in the ortho or para positions. For the Suzuki-Miyaura reactions, both sets of PdNPs revealed slightly higher yields for the products synthesized using the bromo substrate (>90%), while low yields (40 – 55% yields) were obtained for the ortho substituted substrate in comparison to the para substrate (>90% yields). The Heck coupling reactions with butyl acrylate and 4-iodoacetphenone were successful (~70% yields), while reactions with 4-bromoacetophenone failed. However, the Sonogashira couplings did not proceed at all. With the series of reactions NPs showed some selectivity, with the AE-PdNPs consistently producing higher yields for the products obtained. This may be due to overall nature of the NPs, or due to the higher platinum loading content for the AE-PdNPs.

Hybrid materials synthesized by grafting of organic molecules onto silica surface have found numerous applications in chemistry, biochemistry, and chemical engineering. In particular, the functionalization of silica gel can be accomplished by various surface reactions of immobilized boronic acids. Suzuki coupling has been chosen due to several advantages, such as mild reaction conditions, tolerance to the aqueous environment, and high yields of the products. The objective of this work was to determine the most effective reaction conditions for modifying porous hybrid materials with large specific surface areas and high density of surface organoboron reactive sites by various functional groups. Prior to modification by Suzuki coupling, the surface of silica gel was functionalized by phenylboronic acid. Two methods were tested for immobilization of phenylboronic acid: hydrosilylation and thiol-ene coupling. The later radical reaction between surface alkylthiol groups and 4-vinylphenylboronic acid was found more effective. Obtained boronated silica gel was used for further functionalization by various aryl halides. Surface Suzuki coupling reaction was catalyzed by palladium acetate in the presence of cesium carbonate as a base, while dimethylformamide was chosen as a solvent. The coupling reactions proceeded at mild heating under constant sonication. Such ultrasonic irradiation was reported earlier to have an activating effect on Suzuki coupling. The analysis of the obtained products indicated formation of surface biaryl compounds, the highest yields have been obtained in reactions with iodobenzene and bromobenzene. Thus, novel functionalized organic/inorganic hybrid materials were successfully synthesized by surface modification of mesoporous silica gel.

Mesoporous silica gel was functionalized by various organic functional groups using thiol-ene coupling of surface thiol groups with 4-vinylphenylboronic acid followed by Suzuki coupling with aromatic halides. For better performance, the synthesis was conducted under sonication. The presence of surface functional groups was confirmed by thermoanalysis, FT-IR spectroscopy and characteristic reactions of these groups. Solid-phase conditions of the synthesis eliminate the risk of side reactions of boronic acids.

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Non-ionic deep eutectic solvent (ni-DES) possesses various advantages such as good solvation, biodegradability, and non-toxicity which makes it a perfect and environmentally friendly solvent for organic synthesis. A Pd (OAc)2 catalyzed, Suzuki reaction of aryl bromide and N-heteroaryl halide with arylboronic acid in green and novel solvent (ni-DES) is described. In this work, the possibility of using ni-DES and the impact of this solvent on the scope of the reaction is studied. It is illustrated that using the mixture of N-alkyl derivatives of urea and acetamide as a green solvent for Suzuki reaction is achievable even though the desired amount of product was not obtained. However, the high yield in ni-DES can be obtained by choosing 4-bromobenzotrifluoride or 4-bromoanisole as the aryl bromide with arylboronic acid that possess the electron donating groups. Despite that, for getting more yield through Suzuki reaction in ni-DES more studies on optimization are required.

In chapter 1, we describe development of a mild and efficient method for SNAr iodination of 6-chloropurine 2'-deoxynucleosides and nucleosides. Our studies demonstrate that 6-iodopurine nucleosides are excellent substrates for certain transition metal-catalyzed cross-coupling reactions. In chapter 2, we describe synthesis of protected 6-fluoro, 6-chloro, 6-bromo and 6-sulfonylpurine nucleosides. Comparisons among 6-fluoro-, 6-chloro-, 6-bromo, 6-iodo and 6-sulfonylpurine nucleosides for SNAr reactions with various N, O and S nucleophiles were investigated. Our results demonstrate that the 6-fluoropurine nucleoside is the best substrate for SNAr reactions among the four 6-halopurine nucleosides with oxygen, sulfur and aliphatic amine nucleophiles, and also with an aromatic amine plus TFA as a catalyst. However, the 6-iodopurine nucleoside is the best substrate for the aromatic amine without acid. With oxygen and sulfur nucleophiles, the 6-sulfonylpurine nucleoside reacted even faster than the 6-fluoropurine nucleoside. In chapters 3 and 4, nickel- and palladium-based systems with imidazolium-carbene ligands can catalyze efficient Suzuki cross-couplings of arylboronic acids and 6-[(imidazol-1-yl)-, (1,2,4-trizaol-4-yl), fluoro, alkylsulfanyl and alkylsulfonyl]purine 2'-deoxynucleosides and nucleosides to give the corresponding 6-arylpurine products.

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La récupération et le recyclage des catalyseurs représentent un véritable challenge économique, sanitaire et environnemental. Depuis quelques années, l’utilisation des nanoparticules magnétiques comme support de catalyseurs a émergé comme une voie alternative pour leur recyclage. En effet, les catalyseurs supportés sur des nanoparticules magnétiques peuvent être facilement isolés et recyclés par décantation magnétique avec un simple aimant. Dans ce travail, nous décrivons la synthèse de métallodendrons porteurs de site catalytiques diphosphinopalladium et leur greffage sur des nanoparticules magnétiques cœur-écorce. L’intérêt majeur de ce travail a été de montrer la grande efficacité du recyclage des catalyseurs notamment en milieu aqueux. L’utilisation judicieuse des structures dendritiques a permis d’augmenter la fonctionnalisation de la surface des MNPs. Ceci nous a permis de préparer des catalyseurs supportés très performants dans des réactions de couplage de Suzuki et de Sonogashira / The recovery and recycling of catalysts represent a real challenge for economic, health and environmental reasons. Since few years, the use of magnetic nanoparticles as catalysts supports has emerged as an alternative for their recovery. Indeed, magnetic nanoparticles-supported catalysts could be easily isolated and recycled from the reaction medium by magnetization with a simple magnet. In this work, we report the synthesis of metallodendrons bearing pallado phosphine catalysts and their grafting onto core-shell magnetic nanoparticles. The main interest of this work was to demonstrate the efficiency of the recycling especially in aqueous media. Judicious use of dendritic structures has increased the surface functionalization of nanoparticles. Therefore, it was possible to prepare highly performant catalysts for Suzuki and Sonogashira cross-coupling reactions.