This thesis is composed of two central themes of research Chapters 2-6 describe efforts to understand and increase the activity of iminium ion catalysts. Chapters 7-9 are free-standing investigations exploring concepts and observations that were encountered through the course of the research. Chapter 1 briefly introduces iminium ion catalysis before discussing the experimental and theoretical techniques that are routinely applied to investigate reaction mechanism. The discussion of techniques is divided into three sections structural, kinetic and theoretical methods. This is followed by a passage that highlights the reported techniques that have been applied to understand mechanisms of iminium ion catalysed processes. Chapter 2 highlights the work previously conducted within the group developing catalysts for the iminium ion catalysed Diels-Alder reaction and describes a SAR study designed to understand the relationship between the cc-effect and P-EWG components of catalysts to aid future catalyst design. The study found that the components work independently. Chapter 3 describes a further SAR study conducted to provide evidence for the role of the P-EWG in increasing catalyst activity. The important conclusions drawn were that P-EWG was not acting as a proton shuttle as previously hypothesised and that EWG's that do not contain a carbonyl group could be exploited to increase the activity of a catalyst. Chapter 4 describes investigations into mechanistic aspects of the catalytic cycle for the iminium ion catalysed Diels-Alder reaction. The isolation of key iminium ion intermediate allowed for structural studies and kinetic investigations of the individual steps of the catalytic cycle. The Diels-Alder cycloaddition was found to be the RDS and the physical reasons for this were understood. The hypothesis was formed that a lowering in the LUMO energy of the dienophile by including a strong p-EWG into the catalyst would accelerate the overall catalytic cycle. Chapter 5 describes the application of our findings to the design and synthesis of more active catalysts based around the scaffold of MacMillans imidazolidinone catalyst. The inclusion of an additional p-EWG within the catalyst scaffold provided unprecedented levels of activity supporting our hypothesis. The development and evaluation of a predictive theoretical tool for catalytic activity is also discussed. Chapter 6 shows the preliminary development of piperazinones as catalyst for the iminium ion catalysed Diels-Alder reaction of aldehydes and ketones. Chapter 1 describes our efforts to develop a chiral dynamic resolution procedure for the iminium ion catalysed Michael addition reaction of nitroalkanes to cc,p-unsaturated ketones. Chapter 8 reports the development of a one-pot monocarboxymethylation procedure for primary amines and diamines using glyoxylic acid under mild conditions. Chapter 9 describes the first aminocatalytic method for the preparation of non-natural and natural bis-indolyl alkanes.

Due to the environmental problems arising from the combustion of fossil fuels and their depletion, the production and use of renewable fuels have grown rapidly in recent years. Hydrogen is among the promising fuels of the future as the only material that can be produced from the burning of hydrogen in air is water. The production of hydrogen by the photocatalytic water splitting method involving a semiconductor is a promising development in the field of energy and the environment, and this technique was employed in this work. TiO₂ and palladium were the main photoactive support and loaded metal used in this project, respectively. The hydrogen production, whether from water/methanol solution or water alone, was investigated by illumination of the catalyst by UV irradiation produced from an Xe arc lamp. The reactions were performed in liquid or gas phase under an argon atmosphere as an inert gas. The gaseous products were collected and analysed using gas chromatography. The main method used in Pd loading was the impregnation method. 0.5% and 0.1% wt Pd loading were the best in terms of hydrogen production rate in liquid and gas phase reactions respectively. 0.5% Pd/TiO₂ (P25) was used in the remaining experiments to investigate some of the variables, to maximize the rate of H₂ production. Glycerol displayed an activity and produced hydrogen and carbon dioxide, as in the case of methanol but in much higher quantities. Loading of mesoporous TiO₂ by a different weight of Pd, which had a high surface area, gave less hydrogen than Pd/P25 whether in liquid or gas phase reactions. The efficiency of Pd loaded titania (P25, pure anatase or anatase prepared by CHFS) doped by non-metals such as nitrogen, silver or strontium was low and less than Pd/TiO₂. Hydrogen produced over Pd/TiO₂, Au/TiO₂ and TiO₂ from water photolysis was also very low. The recombination between hydrogen and oxygen (back reaction) was studied over these catalysts and it was found that it was fastest on Pd/TiO₂ whether in the dark or in the presence of light. For Au/TiO₂, the light enhanced the hydrogen and oxygen reaction.

In Chapters 6 and 7, efforts to develop a predictive computational model for imidazolidinone catalyst activity is described based around the experimental results obtained previously in the thesis. The knowledge gained was then used to design structures with the potential to exhibit high turnovers and extremely high levels of stereoselectivity. Expansion of this model to encompass <italic> C₂</italic>-symmetric catalysts was further explored in Chapter 8.

The selective oxidation of methanol to formaldehyde, the oxidative dehydrogenation of ethane and the oxidative dehydrogenation of propane have been investigated using niobium based catalysts. It has been shown that niobium oxides prepared by different methods show in general a low conversion of reactant in all probe reactions investigated. However, high selectivity to the desired products are maintained (i.e. formaldehyde, ethylene and propene) at elevated temperatures. The introduction of phosphorus into niobium based catalysts enhanced the catalytic performance of the catalyst The aim was to maintain a high selectivity of desirable products whilst increasing conversion. Two sets on niobium and phosphorus based catalysts were investigated. The first set of catalyst was niobium oxide phosphates, NbOPC>4, prepared from a method which was analogous to VPO work. Catalytic testing of the niobium oxide phosphates showed an increased conversion in both methanol oxidation and ethane oxidative dehydrogenation. However, there was little effect in using niobium oxide phosphates for the oxidative dehydrogenation of propane. Comparing niobium oxide phosphates to niobium oxides, the conversion doubled with respect to oxidative dehydrogenation of ethane and increased 18-fold with respect to methanol oxidation. The second set of niobium and phosphorus based catalysts were niobium phosphates, NbPOs. These were prepared from the reduction of niobium oxide phosphates. Catalytic testing showed an increased conversion in both methanol oxidation and ethane oxidative dehydrogenation. This is the first time that niobium phosphates and oxyphosphates have been investigated as catalysts and they demonstrate appreciable activity for a range of selective oxidation reactions.

This thesis describes the synthesis of a number of functionalised imidazolium salts as precursors to N- heterocyclic carbenes and their subsequent coordination to Ag and Pd. Further a number of the Pd complexes were tested in the Heck reaction and their activities compared to complexes with similar structural features currently within the literature. A range of imidazolium salts have been synthesised which include quinoline and octahydroacridine moieties and have been characterised by a number of methods including X-ray crystallography. A bis imidazolium salt has also been prepared as a DIOP analogue. The imidazolium salts were successfully reacted with Ag20 to form the NHCAg(I) complexes. The quinoline and octahydroacridine based NHCs were transmetallated to Pd as chelating ligands, the quinoline based systems appearing as planar, strained complexes in the X-ray structure. The activities of the quinoline and octahydroacridine based NHCPd(II) complexes in the Heck coupling of 4-bromoacetophenone and 4-chlorobenzaldehyde with n-butyl acrylate were assessed and found to be comparable to similar systems with low to satisfactory conversions.

This thesis embraces three main sections: the development of new molecular scaffolds for the organocatalytic Diels-Alder reaction, extension of the studies upon the a-effect and ji-stacking interactions to acyl-ammonium catalysis and development of novel molecular structures for the aminocatalysed Baylis-Hillman reaction. Chapter 1 describes some of the recent advances made in metal-free asymmetric catalysis and sets the work involved within this thesis into context. Chapter 2 describes the investigation of the a-effect and the modulation of face-face ji-jt interactions as a platform for the development of a novel family of catalyst for the aminocatalysed Diels-Alder reaction. After initial investigation on the effect of different counter anions and alternative electron withdrawing groups within achiral catalysts, the a-effect and the face-face ji-jt interactions design concepts were combined within the structure of a series of arenes based on the 8-aryl menthamine scaffold. Experiments performed utilising (L)-cinnamaldehyde and cyclopentadiene provided clear indications that the ji-stacking interaction incorporated within the architecture of the catalyst cloud drive the geometric control of the Diels-Alder adducts, showing a 54% ee (25) utilising the naphthyl group as the aryl unit and a 30% ee (2R) with the 4-TVyV-dimethyl aniline based catalyst. Within Chapter 3 investigations into the a-effect was extended to an acyl-ammonium catalysis by preparation of a series of 4-aminopyridines containing a heteroatom in the ct-position to the N'-1 nitrogen atom. Examination of this series of catalysts in the acylation of 1-cyclohexanol with acetic anhydride revealed that the a-effect has a detrimental effect in terms of reactivity. Moreover, alternative electronic interactions were examined to improve the nucleophilicity of 4aminopyrimidines. Preparation of a novel set of catalysts for the enantioselective acylation of alcohols was also attempted. Chapter 4 describes an investigation into the organocatalysed Baylis-Hillman reaction. Starting from previous work reported in literature, an initial analysis of solvent conditions showed that the presence of small amounts of water in organic solvents significantly improves the reactivity for the reaction catalysed by (5)-proline and imidazole to give up to a 80%. A series of (S)-proline and (5)-histidine derivatives were also investigated as an alternative to the catalytic system (S)-proline/imidazole for the asymmetric Baylis-Hillman reaction, providing an enantiomeric excess of 22% ee (R) with the 2-(2,3,4,5,6-pentafluorobenzamido)-(5)-histidine methyl ester derivative. Minor modification to this class of catalyst also showed that the presence of second amide unit significantly improved the reaction efficiency providing a pleasing 79% yield for the reaction performed in tetrahydrofuran. Finally, the catalytic system of (5)-proline/imidazole was combined into the structure of the dipeptide (S)- proline-(S)-histidine and was also examined as a potential catalyst for the asymmetric Baylis-Hillman reaction.

The catalytic oxidation of carbon monoxide is an important reaction in heterogeneous catalysis. Copper manganese mixed oxides in the form of Hopcalite, CuMn₂C₄, is used as a catalyst for the oxidation at ambient temperature and is important in respiratory protection, particularly in mining industries. These types of catalysts are prepared by a co-precipitation method variables in this preparation procedure are known to control catalytic activity. Previous work has shown that the addition of a cobalt dopant metal to the catalyst structure can have a positive effect on activity towards CO oxidation. This thesis furthers the work of dopant addition by studying the effects of zinc on the copper manganese catalyst. Catalyst testing for CO oxidation showed that the addition of the zinc dopant metal increases the stability of catalytic activity. Temperature Programmed Reduction studies show that the addition of zinc has an effect on the redox properties of the catalyst. Prepared copper manganese oxide catalysts were used as supports for gold catalysts. Gold supported CuMnOx was prepared by a deposition precipitation method. The addition of gold to these active materials leads to a marked increase in the catalytic activity. Scanning Electron Microscopy (SEM) showed that the morphology of the support used, played an important role in producing a highly active catalyst. Also, the ageing time of the catalyst precursor was shown to influence catalytic activity. The most effective catalyst for CO oxidation was found to be a 1 wt% Au supported catalyst. The presence of moisture in the gas feed is known to be detrimental to a Hopcalite catalyst for ambient temperature CO oxidation. The effect of moisture on the copper manganese mixed oxide catalysts highlighted the improvement in moisture tolerance with the addition of gold. The method of depositing gold onto an oxide support was shown to be applicable to a commercially available catalyst. The gold supported CuMnOx catalysts prepared were tested for oxidation reactions at higher temperatures. The reactions investigated were ethylene oxide oxidation and preferential oxidation (PROX) of carbon monoxide. Studies showed the addition of gold to the CuMnOx catalysts, improves activity compared to an undoped catalyst.

Vanadium phosphate catalysts have successfully been prepared in aqueous media using hydrogen. The catalysts precursors obtained were poorly crystalline VOHPO₄.05H₂O and a minor amount of an impurity detected by a reflection in the XRD pattern. Activating these materials for n-butane oxidation show low selectivity of MA (5%), which could be attributed to the presence of V(V) phases after activation.

The selective and nonselective oxidation of propane was investigated using a range of metal oxide catalysts. Total oxidation of propane was studied using Nb and W supported on Pd/Ti02- The addition of Nb or W to Pd/TiO₂ promoted the activity of the catalyst to give 100% conversion by 450&deg;C. The only reaction product observed was carbon dioxide. The addition of Nb and W significantly changed the nature of the palladium and oxygen mobility, from XPS studies. Niobium and tungsten exhibited the highest activity with a 6% loading with the best catalyst being 0.5%Pd/6%Nb₂O₅/TiO₂. Oxidative dehydrogenation of propane was studied using vanadium on a ceria support and also with cobalt, iron and manganese oxides. Ceria on its own was very active for the total oxidation of propane, under the conditions used for oxidative dehydrogenation, but the sole reaction product was carbon dioxide. The addition of vanadium switched the activity of the ceria to give appreciable selectivity to propene of around 90%. The formation of a mixed cerium vanadium phase was of the most interest for future work where conditions could be optimised to give improved yields. Cobalt, iron and manganese oxides were prepared by grinding the corresponding nitrate with ammonium bicarbonate and their activity tested in propane oxidative dehydrogenation. The yields of propene were higher than the V/CeO₂ catalysts with the most active oxide being cobalt with a yield of 3.8%. The activity of cobalt was attributed to a small crystallite size, high reducibility and high ratio of O/Co. Methanol oxidation was also investigated using the cobalt, iron and manganese oxides. The main reaction product was formaldehyde and the highest yield, of 23%, was obtained for the manganese oxide. The activity was attributed to a high O/Mn ratio of 3.03 and an optimal particle size of 54nm.

Studies of CO, methanol and some higher alcohol oxidations over gold supported on TiO₂ (Degussa), Y-AI₂O₃ and SiCh were investigated. The methods of preparation of catalysts used are deposition precipitation and incipient wetness impregnation. Several parameters have been investigated for CO oxidation over Au/TiO₂ prepared by deposition precipitation, such as temperature programmed pulse flow reaction, isothermal and continuous flow CO oxidation, anaerobic CO reaction, calcination temperature, effect of moisture (in the presence of water, and methanol), kinetics and CO oxidation in the presence of hydrogen etc. The catalysts are demonstrated to have high activity even at room temperature. Gold supported on TiO₂ (Degussa) was characterized by BET surface area method, powder X-ray diffraction, SEM, EDAX, XPS, and Raman spectroscopy. The CO oxidation reaction studied on A11/Y-AI₂O₃ and Au/SiC catalysts prepared by deposition precipitation (DP) and incipient wetness impregnation (IW) methods showed that the A11/Y-AI₂O₃ catalyst prepared by DP method is much more active than A11/Y-AI₂O₃ and Au/SiC₂ prepared by the incipient wetness impregnation method. Presumably, the low performances of the IW catalysts are ascribed due to presence of chloride which leads to gold sintering in the catalyst. However, the performance of these catalysts with respect to CO oxidation was less than the Au/TiO₂ catalyst prepared by DP method. The characterization of the catalyst shows the BET surface area of A11/Y-AI₂O₃ and Au/SiCh catalysts to be 128 and 320m<super>2</super>/g respectively. The XRD of the A11/Y-AI₂O₃ shows mainly the support, which indicated high dispersion of gold on the catalyst. Nevertheless, XPS, SEM, Raman Spectroscopy and EDAX were used for characterisation of the A11/Y-AI₂O₃ and A11/S1O2 catalysts The CO oxidation reaction studied show that the activity of the catalyst decreases in the following order: Au/ TiCb > A11/Y-AI₂O₃ > Au/SiO₂. The adsorption and reaction of methanol with Au/TiO₂, A11/Y-AI₂O₃ and Au/SiO₂ catalyts using temperature pulse programmed reaction over the reactor, TPD, SEM, EDAX, XPS and DRIFTS were investigated. Several factors were investigated such as pH, calcination, comparison with the reference WGC catalyst, kinetic isotope effect etc. The TiO₂ (P25), Y-AI₂O₃ and SiO₂ surface adsorbed about a half monolayer of methanol, much of it in a dissociative manner forming methoxy groups associated with the cation sites and hydroxy! groups at anions. For, TK2, the methoxy is relatively stable until about 250&deg;C, at which point decomposition occurs, producing mainly dimethyl ether by bimolecular surface reaction. As the concentration of methoxy on the surface diminishes, so the mechanism reverts to a de-oxygenation pathway, producing mainly methane and water (at 330 C in TPD), but also with some coincident CO and hydrogen. In contrast, in the case of Y-AI₂O₃ and SiO₂, dimethyl ether (DME) was observed as the main product. The effect of gold catalysts prepared by DP and IW on the reactivity is marked. The pathway which gives methane, which is characteristic of TiCh (P25) for Au/TiO₂ catalysts, remains the same but a new feature of the reaction is the evolution of CO₂ and H₂ at lower temperature, and the elimination of the DME-producing state. Clearly, this is associated with the presence of gold and appears to be due to the high amount of formate species on the catalyst surface. The formate species involved in the reaction of methanol over TiO₂ and Au/TiO₂ catalysts results in a combustion pathway being followed, with complete conversion occurring by 130&deg;C. Similarly, the main methanol oxidation reaction observed on A11/Y-AI₂O₃ and Au/SiO₂ are dehydration products, mainly, DME, with CO and hydrogen as the main products. The oxidation reaction of higher alcohol (ethanol, propan-l-ol, and propan-2-ol) has been studied over Au/TiC₂ catalyst prepared by deposition precipitation (DP) method using Temperature Programmed Pulsed Flow Reaction, TPD, and DRIFTS. TiO₂ (P25) adsorbed about half monolayer of ethanol, propan-lol and propan-2ol. The presence of the gold (as in the case of Au/TiO₂ catalysts) eliminates most of the dehydration products and increases the production of formate species, which results in a combustion pathway being followed, with complete conversion of ethanol, propan-1-ol and propan-2-ol. Trie results are mainly dehydrogenation, dehydration, de-oxygenation and decomposition products but, in each case, the reaction is a complete oxidation reaction.