<b>Transition Metal Catalyzed Alkylation</b> We have reported methodology for the use of methanol as an alkylation reagent using catalytic rhodium or iridium species for the formation of branched products from methyl ketones. The synthetic utility of the dialkylated products was enhanced by performing a regioselective Baeyer-Villiger oxidation which allowed access to ester products. A range of different phosphine ligands were screened, and sterically hindered and electron rich phosphine ligands were found to favour the formation of enone and methoxy adducts under an O2 atmosphere. This interrupted hydrogen borrowing reaction enabled the in situ addition of a nucleophile to give more complex products. A range of tetrasubsitituted pyridines were then synthesized from 1, 5-dicarbonyl compounds formed in the methylenation/conjugate addition sequence. Finally, deuteration experiments suggest that the reaction proceeds via a monohydride mechanism, and the possibilities for the beneficial effect of O2 were discussed. <b>Synthesis of biotin derivatives</b> The streptavidin-biotin system was chosen for the studies of protein/ligand interactions at molecular level. A series of modified biotin ligands were designed and synthesized to introduce repulsive interations with streptavidin. The protein/ligand complexes were analyzed at high resolution by X-ray crystallography.

<strong>Introduction – Dearomatisation of Heteroaromatic Compounds</strong> The introduction provides a survey of dearomatisation reaction of heteroaromatics, with a particular focus on pyridines/pyridinium salts and furans. The mechanism, scope, and limitations of various approaches are covered, along with the goals of this project. <strong>Results and Discussion – Dearomatisation of Electron-Deficient Heteroaromatics</strong> This chapter initially explores the asymmetric addition of organometallic nucleophiles to pyridinium salts bearing a chiral counterion. Unfortunately, this approach ultimately proved unsuccessful, due to low observed enantioselectivities, and the low solubility of such salts. The second part of this chapter concerns the attempted asymmetric addition of dicarbonyl nucleophiles to electron-deficient furans, under conditions of chiral phase-transfer catalysts, affording bicyclic products in moderate enantioselectivity. Various alternative routes were also explored for the dearomatisation of furans and benzenoid systems. <strong>Introduction – Hydrogen Borrowing Alkylation Reactions with Alcohols</strong> The introduction surveys the range of methods available for the alkylation of various nucleophiles with alcohols under transition metal-catalysed conditions. Related methodologies are also explored, along with methods for the dehydrogenation of methanol. <strong>Results and Discussion - Rhodium-catalysed Methylation of Ketones Using Methanol</strong> This chapter describes the development of a novel ketone α-methylation using methanol. The development of reaction conditions is explored, followed by expansion of the substrate scope, including limitations of the methylation reaction. Mechanistic investigations support a methanol oxidation, aldol reaction/elimination, conjugate reduction pathway. Investigations into the role of O2 in the methylation reaction proved inconclusive. The utility of the reaction was also expanded via one-pot dialkylation reactions (work by Di Shen), Baeyer-Villiger oxidation of the products, and an attempted asymmetric transfer-hydrogenation. <strong>Results and Discussion - Interrupted Hydrogen Borrowing Reactions of Methanol</strong> This chapter looks to intercept intermediates from the α-methylation reaction. The selective methylenation of ketones is described, and a range of nucleophiles are screened for further functionalisation of ketones. Finally, a number of nucleophiles, including nitroalkanes, amines, peroxides and boronic acids are applied to one pot methylenation/conjugate addition protocols, affording complex products after two steps in one reaction vessel. <strong>Experimental</strong> Full experimental procedures and spectroscopic characterisation of compounds are provided.

Due to its unique properties and high surface area, Graphene has become a good candidate as an effective solid support for metal catalysts. The Nobel Prize in Physics for 2010 was awarded to Andre Geim and Konstantin Novoselov "for groundbreaking experiments regarding the two-dimensional material graphene". Microwave-assisted synthesis of various metallic nanostructured materials was investigated for CO oxidation applications. These metallic nanostructured materials were used to convert CO to CO2 as an effective approach for carbon monoxide elimination due to its harmful effect on health and environment. In particular, this dissertation is focusing on palladium as a transition metal that has a unique ability to activate various organic compounds to form new bonds. The prepared graphene-supported metallic nanostructured materials were successfully used to investigate Suzuki cross-coupling reaction as an important reaction in the field of pharmaceutical applications. In this research, nanostructured materials were used as solid support catalysts which showed remarkable improvements in the aspects of size, surface structure, catalytic selectivity, shape and recyclability. The nano porous structure and superparamagnetic behavior of (Fe3O4) nano particles that were used as an effective ingredient in graphene-supported palladium catalyst improved the catalytic activity and the catalyst recyclability simply by using an external magnetic field. This research has been divided into two main categories; the first category is to investigate other metal oxides as a solid support for palladium to be used in CO oxidation catalysis. The second category will focus on improving of solid support systems of palladium – magnetite catalyst to increase recyclability. The final stage of this investigation will study the use of these solid supported metal catalysts in continuous heterogeneous processes under flow reaction conditions. The structural, morphological and physical properties of graphene-based nanocomposites described herein were studied using standard characterization tools such as TEM, SEM, X-ray diffraction, XPS and Raman spectroscopy.

The PhD thesis concerns the synthesis of novel zeolite materials, investigation of their properties and their possible use in catalytic application. The work was focused on the two- dimensional zeolites. The thesis was worked out at the Department of Synthesis and Catalysis at J. Heyrovský Institute of Physical Chemistry, AS CR. Germanosilicate UTL (Si/Ge molar ratio 4.0-6.5) was found to undergo unique structural changes in the neutral or acid environment leading to transformation of its three-dimensional framework into two-dimensional layered material denoted IPC-1P. The UTL degradation, so called top-down synthesis, was enabled due to a presence of double-four-units (D4Rs), which can be seen as supporting units/pillars between the rigid layers. The preferential location of Ge in D4Rs makes the units an ideal target for their selective degradation. The interlayer space in lamellar IPC-1P was modified by swelling with long-organic chain surfactant (material IPC-1SW). To keep the interlayer space permanently expanded (up to 3.3 nm) the silica amorphous pillars were subsequently introduced (material IPC-1PI). The integrity of the layers and their preserved UTL character was confirmed in all members of IPC-1 family by HRTEM and electron diffraction measuring. The layers of IPC-1P were condensed back...

This thesis details investigations into organocatalytic reactions promoted by N Heterocyclic Carbenes (NHCs) that proceed via an assumed azolium enolate intermediate. Initial research focused on the catalytic asymmetric synthesis of β-lactones via an NHC-catalysed formal [2+2] cycloaddition of alkylarylketenes and chloral. This process operated in good yield (typically >70%) and moderate diastereoselectivity (typically ~75:25 dr, anti:syn) for a range of alkylarylketenes. The enantioselectivity was consistently high for the major anti diastereomer (typically >80% ee) and minor syn diastereomer (typically >70% ee). Interestingly, when a ketene bearing a 2 substituent on the aryl ring, or one that included an α-branched alkyl group was used, an exclusive asymmetric chlorination pathway was accessed. This is, to the best of our knowledge, the first use of chloral as an electrophilic chlorination agent. This methodology was found to be applicable to a range of 2-arylsubstituted alkylarylketenes in good yield and enantioselectivity (typically >70% yield and up to 92% ee). The scope of this reaction with respect to the aldehyde moiety was then analysed with 2-nitrobenzaldehyde providing β-lactone products in excellent dr (up to 94:6 syn:anti) and with good yield and enantioselectivity (typically >60% yield and >80% ee). Importantly these β-lactone products were amenable to further derivatisation with transformation to β-amino- and β-hydroxy acids. Following the identification of an NHC-catalysed chlorination reaction using chloral, the development of a general procedure was undertaken. Following a wide screen of electrophilic chlorination sources, 2,3,4,5,6,6 hexachlorocyclohexa 2,4 dienone was identified as optimal, operating in excellent yield (up to 97%) but in moderate to poor levels of enantioselectivity (21−61% ee). Efforts to expand the practicality of azolium enolate processes focused on the use of α-aroyloxyaldehydes as bench stable mono-substituted ketene surrogates. A range of differentially substituted α-aroyloxyaldehydes allowed access to δ-lactones via the NHC-catalysed [4+2] cycloaddition between azolium enolates and β,γ unsaturated α ketoesters. Following initial optimisation the reaction proceeded in exquisite diastereo- and enantiocontrol (typically >95:5 dr and >99% ee).

Doctor of Philosophy / Department of Chemical Engineering / Peter H. Pfromm / Characterization of the interactions of hydrogen with catalytic metal surfaces and the mass transfer processes involved in heterogeneous catalysis are important for catalyst development. Although a range of technologies for studying catalytic surfaces exists, much of it relies on high-vacuum conditions that preclude in-situ research. In contrast, atomic force microscopy (AFM) provides an opportunity for direct observation of surfaces under or near actual reaction conditions. Tapping-mode AFM was explored here because it expands AFM beyond the usual topographic information toward speciation and other more subtle surface information. This work describes using phase-angle data from tapping-mode AFM to follow the interactions of hydrogen with palladium. Both gas-solid and liquid-solid interfaces were studied. Real-time AFM phase-angle data allowed for the observation of multiphase mass transfer to and from the surface of palladium at atmospheric pressure and room temperature without the need for complex sample preparation. The AFM observations were quantitatively benchmarked against and confirm mass transfer predictions based on bulk hydrogen diffusion estimates. Additionally, they support recent studies that demonstrate the existence of multiple hydrogen states during interactions with palladium surfaces.

N-Heterocyclic carbenes (NHCs) have emerged as appropriate replacements for phosphines in transition metal catalyzed cross-coupling chemistry. The advantages of NHCs over phosphines include ease of handling, minimal toxicity, stability and powerful electron donating properties. Improvement of catalytic processes has become increasingly relevant in light of prospective applications of organic transformations in industry as well as in synthetic laboratories. To that end, NHCs represent an important class of catalysts and catalyst modifiers which mandate continued research efforts. Prospective applications of processes catalyzed by NHCs and NHC-metal catalysts provide a strong impetus to develop them and related methodologies. This dissertation focuses on the development of NHCs and NHC ligated metal complexes in various catalytic transformations. NHC ligated palladium catalysts were synthesized in simplified protocols amenable to large-scale industrial applications. The catalysts were utilized in developing different valuable coupling methodologies. Significant advances were achieved in Suzuki-Miyaura, á-arylation of ketones and Kumada-Tamao-Corriu cross coupling reactions. The focus of the work was to make the synthesized catalysts and their activity in these methodologies acceptable to wider range of applications. The strongly nucleophilic nature and easily tunable steric and electronic properties of NHCs have been exploited to mediate organic transformations by utilizing NHCs as catalysts. The metal-free catalysis has an added advantage of being more environmentally friendly. NHCs have proven to be excellent transesterification catalysts for reactions of alcohol and esters. An efficient catalytic system, widening the scope of N-heterocyclic carbenes catalyzed transesterification/acylation reaction of alcohols is described. The methodology has been expanded to include secondary alcohols as well as phosphorus based esters.

N-Heterocyclic Carbenes (NHC) present a viable alternative to traditional phosphine ligands in a variety of organometallic mediated catalytic reactions. Singlet ground-state carbenes are stabilized by the push-pull presence of two adjacent nitrogen atoms in an imidizolium 5-membered ring, allowing neutral electron donor properties. The ability to synthesize a variety of NHC ligands with differing steric and electronic properties is possible by changing the sustiuents on the nitrogen atoms of the imidizolium. Tunable characteristics and enhanced chemical and thermal stability give NHC’s an advantage over phosphines in many catalytic systems. This dissertation focuses on the use N-Hetercyclic Carbenes in a variety of organometallic complexes. The synthesis of NHC complexes with a variety of transition metals is described. The transition metals complexed with NHC’s include palladium, iridium, nickel and ruthenium. The catalytic activity of the metal-NHC complexes is investigated as well.

A dissertation submitted to the Faculty of Science, University of the Wtlwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science / This dissertation focusses on the deactivation of SAP0-34 and modified SAPOs during methanol conversion under various conditions, in comparison to H-ZSM-5. SAPO-34 was found to deactivate rapidly during methanol conversdon. This was shown by the decrease in activity, surface area and pore volume of the catalyst. The deposited "coke" was analysed by in situ diffuse reflectance infra-red Fourier Transform spectroscopy,solid-state magic angle spinning nuclear magnetic resonance, gas chromatography mass spectroscopy (GCMS) of the HF- and dichloromethane-extracted to "coke"; and GCMS of the organic specfes released during regeneration of the catalyst and trapped in resin capillary inlet tubes.The "coke" consisted of alkylated aromatics and naphthalenes which probably formed on the surface or in the large cavities of SAPO-34. The amount of "coke" deposited during methanol conversion increased with reaction temperature, decreased with dilution of the methanol with water or nitrogen. and decreased with increased pressure, Incorporation of Ni into the SAPO framework did not decrease the rate of deactivation, but the "coke" that Has deposited was less bulky than that deposited in SAPO-34. Modification of the SAPO-34 with trlmethyl silylchloride decreased the rate at deactivation of the catalyst. / AC 2018

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the Degree of Doctor of Philosophy. Johannesburg, 2015 / Bimetallic platinum nanoparticles were synthesized for application as anode catalysts for low temperature fuel cells such as direct methanol fuel cells (DMFCs). Two distinct synthesis procedures were used; namely conventional synthesis with post-synthesis heat treatment, and secondly polyol microwave-irradiation without further heat-treatment. The aim was to synthesize interesting and novel bimetallic nanostructures and relate their shape and morphologies to their methanol oxidation reaction (MOR) activities and their CO tolerance. Due to the high cost of the conventional synthesis processes as well as their use of harmful solvents, microwave-irradiation was explored as a possible synthesis procedure. It is a greener and more environmentally friendly approach with possibilities of mass production of the nanoparticles. For both the synthesis procedures, the reducing agent, the precursor salts, surfactants, pH of the solution and molar ratios were varied to determine the effect on the shape, size and ultimately the electrocatalytic activities of the Pt-Co and Pt-Ni nanoparticles. For the conventional synthesis procedure, the main parameter of comparison was the strength of the reducing agents, where NaBH4 and N2H4 were used under the same reaction conditions. In this study, the strength of the reducing agent affected the properties of the Pt-Co and Pt-Ni nanoparticles, such that, the stronger the reducing agent, the higher the degree of alloying and the more electrocatalytically active the materials. The drawback in the conventional synthesis was however low current outputs, in the microamps range, which necessitates a need to explore other synthesis procedures. Microwave-irradiation was thus used as an alternative synthesis procedure in an attempt to produce more active bimetallic platinum nanoparticles. Different reaction parameters were changed in this process to optimize the synthesis process, namely the pH of the solution, the amount of surfactant and the Pt-Ni molar ratio. In changing the reaction parameters, there was an observed change in the structure of the nanoparticles, with an average size in the order of 5 nm and different MOR activities. Furthermore, it was found that the activity was highest for the optimum amount of PVP and NaOH concentration of 500 mg and 1.0 M NaOH. In general, the MW synthesized nanoparticles achieved current values in the microamps to amps range, making it a more attractive synthesis procedure compared to the conventional method. The CO tolerance of the materials is an important aspect, as one of the main drawbacks of the commercial application of fuel cells is the propensity of Pt to get poisoned by CO during the methanol dissociation process. Therefore CO stripping measurements were performed on the MW-irradiated catalysts. The catalysts produced in this work showed good resistance towards CO. In general, the behaviours of the catalysts were dependent on the amount of surfactant and the molar ratio of the starting solution. The mechanism of CO tolerance in this case was determined as the bifunctional model, where the Ni-oxide and Ni-hydroxide species donate O to the electrooxidation of CO to CO2. In conclusion, the study of microwave-irradiated bimetallic nanoparticles performed here, resulted in highly active catalysts, which are even more active than commercial Pt/C nanoparticles.