This thesis concerns the development of metal-free reactions to obtain carbon-heteroatom and carbon-carbon bonds. This is achieved by transferring carbon ligands from hypervalent iodine reagents to suitable nucleophiles. The bulk of the work presented herein concerns arylation of oxygen and nitrogen nucleophiles, using the well-known diaryliodonium salts as aryl sources. In the first project, O-arylation of the oxime ethyl acetohydroxamate was studied. It was found that electron-poor as well as electron-rich aryl moieties could be transferred successfully to this nucleophile. Furthermore, the protocol could be extended to a sequential one-pot synthesis of benzo[b]furans. This method allowed for a fast synthesis of the natural product stemofuran A and formal syntheses of other natural products. In a successive project, O-arylation of hydroxide and aliphatic alkoxides was investigated. It is known that electron-poor aryl moieties can be transferred to these nucleophiles in moderate to high yields. However, combined with more electron-rich diaryliodonium salts, a large amount of side products were formed. These were suppressed upon addition of aryne traps, suggesting that aryne pathways are competing with the desired ligand coupling. It was also observed that secondary alcohols were oxidized to the corresponding ketones. The mechanism for this oxidation was investigated and aryne pathways could be excluded. Instead we suggest that the carbinol hydrogen gets deprotonated via an internal mechanism, after the alkoxide has coordinated to the iodonium salt. Highly sterically congested alkyl aryl ethers could be obtained in high yields by combining tertiary alcohols with ortho-blocked diaryliodonium salts.  Next, N-arylation of secondary acyclic amides was studied using acetanilide as the model substrate. This procedure was suitable for transfer of electron-poor as well as ortho-substituted aryl moieties, but attempts to transfer very electron-rich aryl groups were unsuccessful. On the other hand, the amides displayed a complementary reactivity, allowing phenylation of electron-rich amides.  In the final project, a one-pot synthesis of the cyclic iodonium reagent vinylbenziodoxolone is presented. These compounds have not been explored as reagents earlier. Initial screenings showed that the vinyl moiety could be transferred to nitrocyclohexane with opposite regioselectivity compared to the acyclic analogue of the reagent. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 2: Manuscript.</p>

The production of hydrogen gas, through the process of water splitting,is one of the most promising concepts for the production of clean andrenewable fuel.The introduction of this thesis provides a brief overview of fossil fuelsand the need for an energy transition towards clean and renewable energy.Hydrogen gas is presented as a possible candidate fuel with its productionthrough artificial photosynthesis, being described. However, the highlykinetically demanding key reaction of the process – the water oxidationreaction – requires the use of a catalyst. Hence, a short presentation of differentmolecular water oxidation catalysts previously synthesized is also provided.The second part of the thesis focuses on ruthenium-based molecularcatalysis for water oxidation. Firstly, the design and the catalytic performancefor a new series of catalysts are presented. Secondly, a further study onelectron paramagnetic resonance of a catalyst shows the coordination of awater molecule to a ruthenium centre to generate a 7-coordinated complex atRuIII state. Finally, in an electrochemical study, coupled with nuclear magneticresonance analysis, mass spectrometry and X-ray diffraction spectroscopy, wedemonstrate the ability of a complex to perform an in situ dimerization of twounits in order to generate an active catalyst.The final part of this thesis focuses on immobilisation of first rowtransition metal catalysts on the surface of electrodes for electrochemical wateroxidation. Initially, a copper complex was designed and anchored on a goldsurface electrode. Water oxidation performance was studied byelectrochemistry, while deactivation of the electrode was investigated throughX-ray photoelectron spectroscopy, revealing the loss of the copper complexfrom the electrode during the reaction. Finally, we re-investigated cobaltporphyrin complexes on the surface of the electrode. Against the backgroundof previous report, we show that the decomposition of cobalt porphyrin intocobalt oxide adsorbed on the surface is responsible for the catalytic activity.This result is discussed with regard to the detection limit of various spectroscopic methods. / <p>QC 20170529</p>

Chlorins, as the core structures of chlorophylls, have been extensively studied for harvesting solar energy, fluorescent imaging and photodynamic therapy against cancer. This thesis is concerned with design and synthesis of novel chlorins as antennae for harvesting light and sensitising near infrared lanthanide luminescence. In the first part, a series of chlorin monomers, dimers and polymers were synthesised and their photophysical properties were characterised. The chlorin monomers were substituted with five-membered heterocycles, such as thiophenes and furans. These heterocycles function as auxochromes analogous to the natural ones in chlorophylls, and extend chlorin absorption and emission strongly to the red (up to λem = 680 nm). A borylation method was developed to prepare borylated chlorins, which gave access to directly linked chlorin dimers through Suzuki coupling reaction. Different regioisomers of chlorin dimer were prepared, including β-meso homodimers, meso-meso homodimers and heterodimers. The dimerisation resulted in red-shifted absorption and emission. Chlorin polymerisations were performed both electrochemically and chemically. Bis-thienylchlorins yielded chlorin films and an organic solvent soluble copolymer with hexylthiophene, respectively. These polymers from both polymerisations have red absorptions beyond 700 nm, and might be used as light-harvesting antennae. In the second part, chlorins were used as chromophores to sensitise near infrared lanthanide luminescence. Two types of chlorin-lanthanide dyads were prepared through lanthanide coordination with cyclen derivatives and dipicolinic acids (DPA). The cyclen-based dyads were poorly soluble in water, thus their near infrared emissions were not observed. The other type of complexes was fully soluble in H2O and THF. Both Nd and Yb emission were recorded even upon excitation into the Q bands of chlorins. In the dyads with free base chlorins, the singlet state of chlorins might be involved in the sensitisation of lanthanide luminescence. These DPA-based dyads presented two-color emission based on one chlorin and two-color excitation based on one lanthanide ion. These dyads would enable in theory 4-color imaging. In the last part, a microwave-assisted two-step synthesis was described to prepare dipyrromethanes, which are the key intermediates in the chlorin synthesis. This mild method took advantage of the nucleophilicity of pyrrole and the electrophilicity of N,N-dimethylaminomethyl pyrroles. The usually used acid catalysis is detrimental to many functionalities, thus our methods enable the synthesis of dipyrromethanes with acid sensitive groups or a formyl group.

The work described in this thesis is focused on exploring the efficacy of iridium-catalysed asymmetric hydrogenation of precursors to chiral alcohols and chiral cyclohexanes. A range of allylic alcohols including γ,γ-dialkyl allylic alcohols and (Z)-allylic alcohols were prepared and evaluated in the asymmetric hydrogenation using iridium catalysts resulting in chiral alcohols in high yields and excellent enantioselectivity. This methodology was applied in the formal synthesis of Aliskiren, an efficient renin inhibitor drug, using the asymmetric hydrogenation of an allylic alcohol as a key-step. Another project concerned the dynamic kinetic resolution of racemic secondary allylic alcohols using Ir-N,P catalysts under hydrogenation conditions. A range of secondary allylic alcohols and protected alcohols were evaluated in the asymmetric hydrogenation via dynamic kinetic resolution using Ir-N,P catalysts. The corresponding chiral saturated alcohols were formed in good yield with excellent diastereoselectivites (up to 95/5) and enantioselectivities (&gt;99% ee). The last part of this thesis is directed towards the development of highly regio- and enantioselective asymmetric hydrogenation of 1,4-cyclohexadienes and its application in the preparation of useful chiral cyclohexenone intermediates. Non-functionalised, functionalised and heterocycle-containing cyclohexadienes were evaluated. Good yield of regioselectively mono-hydrogenated silyl protected enol ethers were obtained in most cases with excellent enantioselectivity. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 5: Manuscript.</p>

This thesis has been focused on enzymatic kinetic resolutions and stereoselective oxidative transformations of enallenes catalyzed by PdII. In the first part of the thesis, a detailed discussion on Candida antarctica lipase B (CALB)-catalyzed kinetic resolution (KR) of δ-functionalized alkan-2-acetates is shown. We gained a deeper insight into the mechanism of enzyme-substrate recognition. Changing from an anhydrous solvent to water or a water-containing organic solvent enhanced the enantioselectivity. The effect of –OH was also confirmed by a lipase mutant suggesting that the water molecule mentioned above can be partly mimicked. In the second part of the thesis, we developed an efficient KR for allenic alcohols. On this basis, a novel synthesis of optically pure 2-substituted 2,3-dihydrofurans from allenic alcohols via a Ru-catalyzed cycloisomerization was reported. The developed protocol enabled us to assemble an optically pure precursor for total synthesis with three chiral centers from readily available allenol in 2 days. In the third part, we reported a class of reactions involving C–H cleavage under mild conditions: PdII-catalyzed oxidative transformations of enallenes. These reactions are particularly attractive since a number of meticulous structures have been achieved from readily accessible starting materials. The directing effect of an unsaturated hydrocarbon was found to be key for these transformations. In the final part, we developed the carbonylative insertion reaction discussed in the third part of the thesis into an asymmetric version. By using this methodology, a number of cyclopentenone compounds were obtained in good to excellent enantioselectivity.

This thesis concerns the development of metal-free applications using diaryliodonium salts. The first project describes an arylation protocol of allylic and benzylic alcohols in aqueous media. The method proceeds under mild conditions and the ether products were obtained in moderate to good yields. The methodology was also expanded to include arylation of phenols, giving diaryl ethers in good to excellent yields. In the second project, an arylation method that included a wider range of aliphatic alcohols was developed. The scope of accessible alkyl aryl ethers was studied and included a comparative study of phenylation and nitrophenylation of various alcohols. Finally, a formal metal-free synthesis of butoxycain was performed, illustrating the applicability of the developed method. The third project focused on the limitations and side reactions occurring in Chapter 2 and 3. First, an approach to access symmetric diaryl ethers via arylation of hydroxide was presented. This reaction gave rise to a number of side products, which we hypothesized to originate from aryne-type intermediates. A mechanism for the formation of these side products was suggested, supported by trapping and deuterium labeling experiments. Oxidation of the alcohol to the corresponding ketone was also observed and the mechanism of this interesting side reaction was investigated. The latter was suggested to proceed via an intramolecular oxidation without the involvement of radicals or arynes. The fourth project covers a method to synthesize highly sterically congested alkyl aryl ethers via arylation of tertiary alcohols using diaryliodonium salts. The method displayed a broad scope of tertiary alcohols and was also suitable for fluorinated alcohols. The final project detailed in this thesis deals with C-arylation with diaryliodonium salts, showcasing nitroalkanes as well as a nitro ester as suitable nucleophiles for metal-free arylation. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Manuscript.</p>

<p>This thesis deals with the development of catalytic oxidation reactions utilizing hydrogen peroxide as terminal oxidant. The main focus has been to find flavin catalysts that are easy to handle and stable to store but still able to perform the desired reaction. A variety of dihydroflavins were prepared and the electrochemical oxidation potentials were measured and compared with their catalytic activity.</p><p>A flavin catalyst was applied in the sulfoxidation of allylic and vinylic sulfides by H₂O₂. This transformation was highly chemoselective and the sulfoxides were obtained without formation of other oxidation products. The scope of the reaction was demonstrated by applying the method on substrates with a wide range of functional groups such as a tertiary amine. Another flavin catalyst was immobilized in the ionic liquid [BMIm]PF₆ and used for sulfoxidations by H₂O₂. The chemoselectivity was maintained in this system and the catalyst-ionic liquid system could be recycled several times.</p><p>Finally two bimetallic catalyst systems for the dihydroxylation of alkenes by H₂O₂ were immobilized in the ionic liquid. These systems employed either vanadium acetylacetonate VO(acac)₂or methyl trioxorhenium (MTO) as co-catalysts together with the substrate-selective osmium catalyst. Good to excellent yields of the diols were obtained.</p>

<p>This thesis describes the synthesis of structures related to the capsular polysaccharide of <i>Neisseria meningitidis</i> serogroup A and the synthesis of analogues of mycothiol, a compound produced by <i>Mycobacterium</i> <i>tuberculosis</i>. The first part of the thesis describes the synthesis of structural elements present in the native capsular polysaccharide of <i>Neisseria</i> <i>meningitidis</i> serogroup A. In this part, an improved synthesis of 2-azido-2-deoxy-D-mannopyranose is included. The second part of the thesis describes the formation of stable C-phosphonate analogues related to the capsular polysaccharide. The last part outlines the formation of analogues of mycothiol, where the syntheses of a bicyclic analogue and a thioglycosidic analogue are described.</p>

<p>In order to understand biological processes, to treat and diagnose diseases, find appropriate vaccines and to prevent the outbreak of epidemics, it is essential to obtain more knowledge about carbohydrate structures. This thesis deals with structure and conformation of carbohydrates, analysed by NMR spectroscopy and MD simulations.In the first two papers, the structures of O-antigen polysaccharides (PS) from two different <i>E. coli</i> bacteria were determined using NMR spectroscopy. The O-antigenic PS from <i>E. coli</i> O152 (paper I) consists of branched pentasaccharide repeating units, built up of three different carbohydrate residues and a phosphodiester, whilst the repeating unit of the O-antigen from <i>E. coli</i> O176 (paper II) is built up of a linear tetrasaccharide consisting of two different monosaccharides.</p><p>In papers III and IV, the conformational analysis of different disaccharides is described. Conformational analysis was performed using NMR spectroscopy and MD simulations (paper IV). In paper III four different glucobiosides were studied using coupling constants and Karplus-type relationships. By use of specific ¹³C isotopically labelled derivatives, additional coupling constants were obtained and the number of possible torsion angles was reduced by half. In paper IV, we examine the conformations of two disaccharides that are part of an epitope of malignant cells. From NOE and T-ROE experiments, short proton-proton distances around the glycosidic linkage were estimated. Furthermore, interpretation of the extracted coupling constants using Kaplus relationships gave the values of the torsion angles. As in paper III, isotopically labelled compounds were synthesised in order to enhance the sensitivity of the analysis. Finally, MD simulations were performed and the results were compared with results from NMR data.</p>

<p>In this thesis, the chemistry of compounds containing P-Se bonds has been studied. As a new addition to this class of compounds, H-phosphonoselenoate monoesters, have been introduced and two synthetic pathways for their preparation have been developed.</p><p>The reactivity of H-phosphonoselenoate monoesters towards a variety of condensing agents has been studied. From these, efficient conditions for the synthesis of H-phosphonoselenoate diesters have been developed. The produced diesters have subsequently been used in oxidative transformations, which gave access to the corresponding P(V) compounds, <i>e.g</i>. dinucleoside phosphoroselenoates or dinucleoside phosphoroselenothioates.</p><p>Furthermore, a new selenizing agent, triphenyl phosphoroselenoate, has been developed for selenization of P(III) compounds. This reagent has high solubility in organic solvents and was found to convert phosphite triesters and H-phosphonate diesters efficiently into the corresponding phosphoroselenoate derivatives.</p><p>The selenization of P(III) compounds with triphenyl phosphoroselenoate proceeds through a selenium transfer reaction. A computational study was performed to gain insight into a mechanism for this reaction. The results indicate that the transfer of selenium or sulfur from P(V) to P(III) compounds proceeds most likely <i>via</i> an X-philic attack of the P(III) nucleophile on the chalcogen of the P(V) species. For the transfer of oxygen, the reaction may also proceed <i>via</i> an edge attack on the P=O bond.</p>