The hydroaminomethylation (HAM) reaction converts alkenes into N-alkylated amines and has been well studied for rhodium- and ruthenium-based catalytic systems. Cobalt-based catalytic systems are... Show moreThe hydroaminomethylation (HAM) reaction converts alkenes into N-alkylated amines and has been well studied for rhodium- and ruthenium-based catalytic systems. Cobalt-based catalytic systems are able to perform the essential hydroformylation reaction, but are also known to form very active hydrogenation catalysts, therefore we examined such a system for its potential use in the HAM reaction. Thus, we have quantum-chemically explored the hydrogenation activity of [HCo(CO)(3)] in model reactions with ethene, methyleneamine, formaldehyde, and vinylamine using dispersion-corrected relativistic density functional theory at ZORA-BLYP-D3(BJ)/TZ2P. Our computations reveal essentially identical overall barriers for the catalytic hydrogenation of ethene, formaldehyde, and vinylamine. This strongly suggests that a cobalt-based catalytic system will lack hydrogenation selectivity in experimental HAM reactions. Our HAM experiments with a cobalt-based catalytic system (consisting of Co-2(CO)(8) as cobalt source and P(n-Bu)(3) as ligand) resulted in the formation of the desired N-alkylated amine. However, significant amounts of hydrogenated starting material as well as alcohol (hydrogenated aldehyde) were always formed. The use of cobalt-based catalysts in the HAM reaction to selectively form N-alkylated amines seems therefore not feasible. This confirms our computational prediction and highlights the usefulness of state-of-the-art DFT computations for guiding future experiments. Show less
This thesis describes the use of a combined approach of computational and experimental techniques to gain novel insights to understand the glycosylation reaction and its reactive intermediates. The... Show moreThis thesis describes the use of a combined approach of computational and experimental techniques to gain novel insights to understand the glycosylation reaction and its reactive intermediates. The research in this thesis shows that glycosyl cations can act as reactive intermediates in glycosylation reactions for the introduction of glycosidic linkages. Furthermore, computational and experimental evidence has been provided showing that dioxolenium ions, formed by participation of remote acyl groups, are relevant reactive intermediates and can effectively steer the stereochemical course of glycosylation reactions. Ultimately, the techniques developed and insights gained in these studies were used in the synthesis of a complex mycobacterial glycolipid. The fundamental knowledge presented in this thesis can be further exploited in future synthetic endeavors, delivering more and more complex glycans to fuel glycobiological and glycomedical research. Show less
In the search for sustainable energy solutions, the idea of artificial photosynthesis has been proposed as an approach with which to use water and sunlight to produce hydrogen. Key in the... Show moreIn the search for sustainable energy solutions, the idea of artificial photosynthesis has been proposed as an approach with which to use water and sunlight to produce hydrogen. Key in the development of hydrogen production technologies is the splitting of water using a water oxidation catalyst. In this thesis, the water splitting catalytic process was investigated using a number of different computational techniques. Computationally, the water splitting catalytic process has traditionally been considered statically as a number of snapshots, and in vacuum. The traditional approaches also often include a number of correction factors for the charge carriers in the reaction. But because catalytic processes are dynamic, a novel approach was also developed in this thesis. With this approach, one can examine the dynamic transition from one catalytic intermediate to another, in a fully solvated environment. In optimising water oxidation catalysts it is important to consider the interaction with the surrounding environment, and how this can impact the catalytic reaction. Furthermore, in the new approach all the charge carriers–protons and electrons–are included in a dynamic simulation. These techniques give us a better idea of the things needed in the optimisation of water oxidation catalysts. Show less
Carbohydrates or sugars, the most diverse class of biopolymers, are involved in many different biological processes. To be able to study these processes, well defined sugar structures are required.... Show moreCarbohydrates or sugars, the most diverse class of biopolymers, are involved in many different biological processes. To be able to study these processes, well defined sugar structures are required. The synthesis of these sugar structures is at this moment far from ideal and therefore requires fundamental research, in particular towards the glycosylation reaction. In this reaction a positively charged oxocarbenium ion can be considered as the product forming intermediate, the cation is however commonly reasoned to lead to non-selective reactions and product mixtures. Chemical calculations on the oxocarbenium ion combined with model glycosylations proved the contrary, namely that these oxocarbenium ions are in fact selective. With these results, insight into the glycosylation mechanism is improved. The orientation of specific substituents on the sugar ring proved to have a profound influence on the stability of the oxocarbenium ion and thereby on the stereochemical outcome of glycosylations. Show less
