Change search
Refine search result
12 1 - 50 of 55
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Ahlsten, Nanna
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Transition metal-catalysed enol formation from allylic alcohols: Isomerisation, C−C and C−F bond formations 2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis describes the isomerisation of allylic alcohols into enols and enolates catalysed by transition metal complexes. The transformation has been used to prepare both unsubstituted and α-substituted carbonyl compounds. Significant attention has been given to the mechanistic aspects of the reactions.

    In the first part of this thesis, an environmentally benign procedure for the redox isomerisation of allylic alcohols into ketones is described. The reaction takes place in water and at room temperature using a cationic rhodium complex in combination with water-soluble phosphines. A variety of allylic alcohols could be isomerised in high yields using this procedure.

    The second part describes the combination of an allylic alcohol isomerisation with a C−C bond formation, catalysed by a rhodium complex. In this way, allylic alcohols were coupled with aldehydes and N-tosyl imines forming aldol and Mannich-type products. In addition, homoallylic and bishomoallylic alcohols were for the first time isomerised into the corresponding enolates and coupled using this methodology.

    In the third part of this thesis, the isomerisation of allylic alcohols was coupled with a C−F bond formation using an iridium complex and electrophilic fluorinating reagents. This novel transformation was used to convert allylic alcohols into single regioisomers of α-fluoroketones. The reaction is tolerant to air and water and takes place at room temperature.

    All of the reactions described take place under mild conditions, are operationally simple, and utilise catalysts formed in situ from commercially available metal complexes and ligands.

  • 2.
    Bartholomeyzik, Teresa
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium(II)-Catalyzed Oxidative Carbocyclization/Functionalization of Allenynes2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Palladium catalysis has emerged as an outstanding tool in synthetic organic chemistry for the mild and selective formation of carbon-carbon and carbon-heteroatom bonds. This thesis has been directed towards the extension of palladium(II)-catalyzed carbocyclization chemistry under oxidative conditions. An oxidative carbocyclization/functionalization methodology utilizing boron-containing transmetalation reagents was exploited to convert 1,5-allenynes into either arylated or borylated carbocycles. Two protocols were developed that use minimal amounts of Pd(OAc)2, stoichiometric para-benzoquinone as the oxidant and either bis(pinacolato)diboron or different arylboronic acids under mild conditions. A wide substrate scope is applicable to both methods. When the allenyne substrate bears a propargylic hydrogen, two isomeric functionalized carbocycles can be formed. By controlling the reaction conditions the reaction can be directed towards either of these two isomeric products. Kinetic isotope effect studies suggest that the mechanism leading to the different products proceeds through allylic or propargylic C-H bond cleavage, respectively. Moreover, it was observed that water has an interesting effect on the product selectivity when arylboronic acids are used in the oxidative carbocyclization of allenynes.

  • 3.
    Bartoszewicz, Agnieszka
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Building molecular complexity via tandem Ru-catalyzed reactions of allylic alcohols2009Licentiate thesis, comprehensive summary (Other academic)
  • 4.
    Bielawski, Marcin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Efficient and High-Yielding Routes to Diaryliodonium Salts2008Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis summarizes three novel and general reaction protocols for the synthesis of diaryliodonium salts. All protocols utilize mCPBA as oxidant and the acids used are either TfOH, to obtain triflate salts, or BF3•Et2O that gives the corresponding tetrafluoroborate salts in situ.

    Chapter two describes the reaction of various arenes and aryl iodides, delivering electron-rich and electron-deficient triflates in moderate to excellent yields.

    In chapter three, it is shown that the need of aryl iodides can be circumvented, as molecular iodine can be used together with arenes in a direct one-pot, three-step synthesis of symmetric diaryliodonium triflates.

    The final and fourth chapter describes the development of a sequential one-pot reaction from aryl iodides and boronic acids, delivering symmetric and unsymmetric, electron-rich and electron-deficient iodonium tetrafluoroborates in moderate to excellent yields. This protocol was developed to overcome mechanistic limitations existing in the protocols described in chapter two and three.

    The methodology described in this thesis is the most general, efficient and high-yielding existing up to date, making diaryliodonium salts easily available for various applications in synthesis.

  • 5.
    Buitrago, Elina
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Transition metal catalyzed reduction of ketones2010Licentiate thesis, comprehensive summary (Other academic)
  • 6.
    Bäck, Marcus
    Linköping University, Department of Physics, Chemistry and Biology, Organic Chemistry . Linköping University, The Institute of Technology.
    Design and Synthesis of Hepatitis C Virus NS3 Protease Inhibitors Incorporating a P2 Cyclopentane-Derived Scaffold2006Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis describes the design, synthesis and structure-activity relationships analysis of potential inhibitors targeting the hepatitis C virus (HCV) NS3 protease. Also discussed is the disease caused by HCV infection and the class of enzymes known as proteases. Furthermore are explained why such enzymes can be considered to be suitable targets for developing drugs to combat diseases in general and in particular HCV, focusing on the NS3 protease. Moreover, some strategies used to design protease inhibitors and the desired properties of potential drug candidates are briefly examined. Synthesis of linear and macrocyclic NS3 protease inhibitors comprising a designed trisubstituted cyclopentane moiety as an N-acyl-(4R)-hydroxyproline bioisostere is also addressed, and several very potent and promising compounds are evaluated.

  • 7.
    Cadu, Alban
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Synthetical Organic Chemistry.
    Iridium Catalysed Asymmetric Hydrogenation of Pyridines2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis presents the hydrogenation of substituted pyridines using N,P-ligated iridium catalystsin homogeneous media. These iridium catalysts were developed within this research group in thepast decade. This method of hydrogenation is highly stereoselective, and in several cases good to excellent ees were obtained.The hydrogenation of substituted pyridines was studied: by screening for the catalyst giving thehighest conversion and ee, by optimising the reaction conditions and by attempting to improve existingcatalysts. New substrates were synthesised for this process, in particular alkyl substituted Nprotectedpyridines. Their reduction provided chiral piperidines, which could be used as chiralbuilding blocks once deprotected.

  • 8.
    Carlsson, Andreas
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering. Swedish National Forens Centre NFC, Linkoping, Sweden.
    Synthesis and spectroscopic characterization of emerging synthetic cannabinoids and cathinones2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The application of different analytical techniques is fundamental in forensic drug analysis. In the wake of the occurrence of large numbers of new psychoactive substances possessing similar chemical structures as already known ones, focus has been placed on applied criteria for their univocal identification. These criteria vary, obviously, depending on the applied technique and analytical approach. However, when two or more substances are proven to have similar analytical properties, these criteria no longer apply, which imply that complementary techniques have to be used in their differentiation.

    This work describes the synthesis of some structural analogues to synthetic cannabinoids and cathinones based on the evolving patterns in the illicit drug market. Six synthetic cannabinoids and six synthetic cathinones were synthesized, that, at the time for this study, were not as yet found in drug seizures. Further, a selection of their spectroscopic data is compared to those of already existing analogues; mainly isomers and homologues. The applied techniques were mass spectrometry (MS), Fourier transformed infrared (FTIR, gas phase) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. In total, 59 different compounds were analyzed with the  selected techniques.

    The results from comparison of spectroscopic data showed that isomeric substances may in some cases be difficult to unambiguously identify based only on their GC-MS EI spectra. On the other hand, GC-FTIR demonstrated more distinguishable spectra. The spectra for the homologous compounds showed however, that the GC-FTIR technique was less successful compared to GC-MS. Also a pronounced fragmentation pattern for some of the cathinones was found.

    In conclusion, this thesis highlights the importance of using complementary techniques for the univocal identification of synthetic cannabinoids and cathinones. By increasing the number of analogues investigated, the more may be learnt about the capabilities of different techniques for structural differentiations, and thereby providing important identification criteria leading to trustworthy forensic evidence.

  • 9.
    Danielsson, Jakob
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Stereoselective Nucleophilic Additions to Aldehydes and Synthesis of α-Amino-β- Hydroxy-Esters2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis deals with the development of new reaction methodology as well as stereochemical investigations.

    The first part concerns the investigation of 1,2- and merged 1,2- and 1,3- asymmetric induction in Mukaiyama aldol additions to α-heteroatom and α,β- heteroatom substituted aldehydes respectively. In particular, the unexpected 1,2-syn selectivity obtained in the addition of sterically hindered nucleophiles to α-chloroaldehydes is examined, and an explanation for the observed stereochemical trends is proposed.

    The second part describes the development of a novel entry to α-amino-β- hydroxy esters by a 1,3-dipolar cycloaddition reaction of aldehydes and azomethine ylides, generated by thermolysis of aziridines.

    The third part deals with our efforts to develop a novel entry to vicinal all- carbon quaternary centers, based on an intramolecular domino Heck- carbonylation reaction using tetrasubstituted olefins.

  • 10.
    Dong, Hai
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Efficient carbohydrate synthesis by controlled inversion strategies2006Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The Lattrell-Dax method of nitrite-mediated substitution of carbohydrate triflates is an efficient method to generate structures of inverse configuration. In this study it has been demonstrated that a neighboring equatorial ester group plays a highly important role in this carbohydrate epimerization reaction, inducing the formation of inversion compounds in good yields. Based on this effect, efficient synthetic routes to a range of carbohydrate structures, notably β-D-mannosides and β-D-talosides, were designed. By use of the ester activation effect for neighboring groups, a double parallel as well as a double serial inversion strategy was developed.

  • 11.
    Engström, Karin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Protein engineering of enzymes for improved enantioselectivity and application of engineered enzymes in organic synthesis2010Licentiate thesis, comprehensive summary (Other academic)
  • 12.
    Engström, Olof
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Carbohydrate dynamics and interactions studied by NMR spectroscopy2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The combination of NMR spectroscopy and molecular dynamics (MD) simulations are powerful tools in the studying of bioorganic molecules in solution. In this thesis two such studies are presented with focus on the NMR aspect. The caffeine association to sugars (D-glucose and sucrose) was investigated by NMR titrations and NOESY experiments in paper I. The observations from the NMR experiments confirmed MD simulations showing that the binding occurs by a face-to-face interaction between the aromatic surface of the caffeine and axial protons of the sugar ring. Different sugar molecules and residues have different preferences regarding which side of the sugar ring that are involved in the binding. The sucrose residues bind with only one ring face each whereas β-D-glucopyranose has two sides of similar binding probability and the α-D-glucopyranose has something in between. The MD simulations showed that the driving force of the binding is partly driven by hydration effects that favor the enthalpy of the system. A new approach to calculate NMR relaxation parameters (that is dependent on molecular motions) from computational simulations is presented in paper II. Each sugar residue is assumed to be a rigid unit connected by flexible joints in the approach, thus the name diffusive chain model (DCM). The simplified model together with a stochastic simulation approach lowers the computational cost which makes it possible to acquire long enough trajectories to the calculations of spin relaxation parameters. Two case studies with slightly different methodologies are presented. In one of them, spin relaxation parameters are reproduced for the human milk oligosaccharide LNF-1 in a feasible way by the use of Brownian dynamics.

  • 13.
    Fontana, Carolina
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Structural studies of glycans by NMR spectroscopy2012Licentiate thesis, comprehensive summary (Other academic)
  • 14.
    Hagberg, Daniel
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Synthesis of Organic Chromophores for Dye Sensitized Solar Cells2007Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis is divided into four parts with organic chromophores for dye sensitized solar cells as the common feature and an introduction with general concepts of the dye sensitized solar cells.

    The first part of the thesis describes the development of an efficient organic chromophore for dye sensitized solar cells. The chromophore consists of a triphenylamine moiety as an electron donor, a conjugated linker with a thiophene moiety and cyanoacrylic acid as an electron acceptor and anchoring group. During this work a strategy to obtain an efficient sensitizer was developed. Alternating the donor, linker or acceptor moieties independently, would give us the tool to tune the HOMO and LUMO energy levels of the chromophores. The following parts of this thesis regard this development strategy.

    The second part describes the contributions to the HOMO and LUMO energy levels when alternating the linker moiety. By varying the linker the HOMO and LUMO energy levels was indeed shifted. Unexpected effects of the solar cell performances when increasing the linker length were revealed, however.

    The third part describes the investigation of an alternative acceptor group, rhodanine-3-acetic acid, in combination with different linker lengths. The HOMO and LUMO energy level tuning was once again successfully shifted. The poor electronic coupling of the acceptor group to the semiconductor surface proved to be a problem for the overall efficiency of the solar cell, however.

    The fourth part describes the contributions from different donor groups to the HOMO and LUMO energy levels and has so far been the most successful in terms of reaching high efficiencies in the solar cell. A top overall efficiency of 7.1 % was achieved.

  • 15.
    Ilchenko, Nadia
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Development of Catalytic ElectrophilicTrifluoromethylation and Fluorination Methods2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is focused on development of new catalytic, electrophilic fluorination and trifluoromethylation methods of alkenes. These reactions were carried out using hypervalent trifluoromethyl and fluoroiodine reagents.

    The first project involved copper catalyzed oxytrifluoromethylation of terminal alkenes and alkynes. In this reaction the employed hypervalent iodine underwent a formal addition to C-C multiple bonds. Subsequently, we have also shown that under similar reaction conditions in the presence of B2pin2 as additive quinones can smoothly undergo C-H trifluoromethylation.

    We also developed a cyanotrifluoromethylation reaction of styrenes, which proceds in the presence of copper cyanide and PCy3 as additive. This reaction allows addition of both trifluoromethyl and cyanofunctionality to the styrene, creating two new carbon-carbon bonds.

    The interesting substituent effects and the acceleration of B2pin2 and PCy3 additives inspired us to further investigate the mechanism for the above trifluoromethylation reactions. The Hammett studies showed that the oxytrifluoromethylation reactions are slightly accelerated by electron donor substituents. The C-H trifluoromethylation does not show deuterium isotope effect. Both B2pin2 and PCy3 accelerated the trifluoromethylation reactions but the extent of the acceleration was dependent on the reaction type and on the substituent effects.

    Inspired by our trifluoromethylation results, we have also studied the silver-mediated difluorination of styrenes in the presence of an electrophilic hypervalent iodine based fluorine source. We obtained over 50% of the difluorinated product which suggests that one fluorine atom comes from the fluoroiodine reagent and the other one from BF4-. A phenonium ion intermediate has been proposed to be involved in the mechanism of the difluorination reaction.

  • 16.
    Jalalian, Nazli
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis and applications of diaryliodonium salts2010Licentiate thesis, comprehensive summary (Other academic)
  • 17.
    Janson, Pär G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Metal-catalyzed oxidative formation of C-CF3 and C-O bonds in alkenes and alkynes2012Licentiate thesis, comprehensive summary (Other academic)
  • 18.
    Jiang, Tuo
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium(II)-catalyzed oxidativecarbocyclization: Functionalization with Boron-Containing Reagents2012Licentiate thesis, comprehensive summary (Other academic)
  • 19.
    Johnston, Eric
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Biomimetic oxidation methods: Efficient reoxidation of palladium and ruthenium by the use of a hybrid electron transfer catalyst.2009Licentiate thesis, comprehensive summary (Other academic)
  • 20.
    Karlsson, Erik
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Catalytic Oxidation Methods. Use of inexpensive and environmentally friendly Oxidants in organic Synthesis.2009Licentiate thesis, comprehensive summary (Other academic)
  • 21.
    Kerdphon, Sutthichat
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    N-Heterocyclic Carbene-Phosphine Iridium Catalyzed Alkylation Reactions and Asymmetric Hydrogenation of Ketones2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is focused on hydrogen transfer reactions using N-heterocyclic carbenephosphine iridium catalysts and is divided in two parts. The first part describes the use of achiral N-heterocyclic carbene-phosphine iridium complexes catalyzing the methylation of ketones and alkylation of amides using alcohols as the electrophile. In Chapter 2, the N-heterocyclic carbene-phosphine iridium complexes that have been developed in the Andersson group was employed as catalysts for the methylation of ketones. These reactions were found to take place under mild conditions with low catalyst loading (1.0 mol%) to furnish the desired methylated products in up to 98% isolated yield. The achiral N-heterocyclic carbene-phosphine iridium complexes were also found to catalyze the N-alkylation of amides with alcohols, as presented in Chapter 3. It was discovered that the reactivity of the catalysts was highly dependent on the structure of the catalyst. At optimum reaction conditions, the best catalyst could be used with a wide range of substrates at low catalyst loading (0.5 mol%) to afford the desired product up to 98% isolated yield.

    The second part of this thesis details the preparation of chiral N-heterocyclic carbenephosphine iridium complexes and their use in the asymmetric hydrogenation of ketones (Chapter 4). These catalysts were successfully used in the asymmetric hydrogenation of ketones at room temperature under base-free conditions and led to full conversion of chiral alcohol products in 30 min with high enantiomeric excess (up to 96%).

  • 22.
    Kärkäs, Markus
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bio-inspired metal complexes: Their synthesis and application in light-driven water oxidation and organic transformations2010Licentiate thesis, comprehensive summary (Other academic)
  • 23.
    Larsson, Johanna M
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium-catalyzed C-H functionalization of alkenes under oxidative conditions2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The unique properties of high oxidation state palladium have been used to develop new catalytic alkene C-H functionalization reactions. A Heck-type coupling based on the reactivity of palladium catalysts and diaryliodonium salts has been developed with broad synthetic scope and tolerance for functional groups that are ordinarily reactive in Pd0/PdII catalysis, for example, allylic acetates and aryl bromides. Poisoning experiments and DFT studies suggest that a PdII/PdIV cycle is operating. The first catalytic allylic C-H silylation method has also been developed utilizing commercially available hexamethyldisilane as silyl source and iodine(III) reagents as oxidants.

  • 24.
    Larsson, Rikard
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Reversible Sulfur Reactions in Pre-Equilibrated and Catalytic Self-Screening Dynamic Combinatorial Chemistry Protocols2006Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Dynamic Combinatorial Chemistry (DCC) is a recently introduced supramolecular approach to generate dynamically interchanging libraries of compounds. These libraries are made of different building blocks that reversibly interact with one another and spontaneously assemble to encompass all possible combinations. If a target molecule, for instance a receptor is added to the system and one or more molecules show affinity to the target species, these compounds will, according to Le Châtelier´s principle, be amplified on the expense of the other non-bonding constituents. To date, only a handful of different systems and formats have been used. Hence, to further advance the technique, especially when biological systems are targeted, new reaction types and new screening methods are necessary. This thesis describes the development of reversible sulfur reactions, thiol/disulfide interchange and transthiolesterification (the latter being a new reaction type for DCC), as means of generating reversible covalent bond reactions. Two different types of target proteins are used, enzymes belonging to the hydrolase family and the plant lectin Concanavalin A. Furthermore, two new screening/analysis methods not previously used in DCC are also presented; the quartz crystal microbalance (QCM)-technique and catalytic self-screening.

  • 25.
    Lihammar, Richard
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Chemoenzymatic Dynamic Kinetic Resolution of Functionalized Secondary Alcohols2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Dynamic kinetic resolution (DKR) is the combination of a kinetic resolution with an in situ racemization and is a powerful method for obtaining optically active compounds. In this thesis various secondary alcohols are transformed to their corresponding enantiomerically enriched acetates by employing immobilized lipases as resolution catalysts and transition metal complexes as racemization catalysts.

    In the first part 3-hydroxypiperidines and 3-hydroxypyrrolidines are transformed to their corresponding acetates in high yields and high enantiomeric excesses using the DKR method. This was the first report of DKR on these types of N-heterocycles. It was found that the immobilization method used has a significant impact on the enzyme selectivity and reactivity.

    In the second part, cyclic allylic alcohols are investigated as substrates for DKR. After optimization, the amount of enone by-product could be reduced to <10% and a range of allylic alcohols could be converted to enantiomerically pure allylic acetates in high ee. The possibility of further transformation of an iodo-substituted substrate was investigated and initial results obtained are promising. Electron-rich allylic alcohols are not suitable for this method due to competing formation of homo coupled ether.

    DKR has also been applied in the total synthesis of Duloxetine, the active species of the pharmaceutical CymbaltaTM. CymbaltaTM is administered as a drug against physical disorder like depression, stress urinary incontinence, and obsessive compulsive disorder. By performing a sixs tep synthesis, utilizing DKR in the enantiodetermining step, Duloxetine could be isolated in an overall yield of 37% and an enantiomeric excess above 96%.

  • 26.
    Lind, Maria E.S.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Quantum Chemical Modeling of Asymmetric Enzymatic Reactions: Applications to Limonene Epoxide Hydrolase and Arylmalonate Decarboxylase2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis, density functional theory has been employed to study the reactionmechanisms of two enzymes with possible applications in asymmetric biocatalysis.To reproduce and rationalize the stereoselectivity of the enzymes, quite large cluster models that account for the chiral environment of the active site have been used.

    In the first study, the enantioselectivity of the wild-type limonene epoxidehydrolase and two groups of mutants thereof, that show either (R,R)- or (S,S)-selectivity, were investigated. Using the cluster approach, the enantioselectivity for each variant of the enzyme was calculated and the results are in good agreement with the experimental data. It was found that the enantioselectivity of the enzyme variants is controlled by the steric hindrance introduced or relieved bythe different mutations.

    The second study concerns the reaction mechanism and stereoselectivity of arylmalonate decarboxylase. The calculations support the proposed two-step mechanism, in which decarboxylation and protonation of the substrate occur separately. The stereoselectivity of the enzyme is governed by repulsive steric interactions between the substrate and the residues that deffine a large and a small cavity in the active site. Depending on the size of the substrate, the selectivity was found to be determined already at the binding of the substrate or in the subsequent transition state.

    The results presented in this thesis demonstrate that the quantum chemical cluster approach for modeling enzymes is indeed a very valuable tool in the study of asymmetric biocatalysis.

  • 27.
    Lindstedt, Erik
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of Aryl Ethers: Metal-Free Arylation of Alcohols using Diaryliodonium Salts2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis contains two parts showing different metal-free methods to synthesize aryl ethers using hypervalent iodine reagents, more specifically diaryliodonium salts. The first part describes arylation of benzylic and allylic alcohols and phenols in water using the easily accessible base sodium hydroxide. Chemoselectivity of phenols in aqueous media is discussed and limitations of the reaction are presented.

    The second part describes an arylation of aliphatic alcohols at room temperature with short reaction time and no excess of reagents are required. The scope of the methodology was investigated and showed that electron-deficient iodonium salts worked efficiently, but unfortunately electron-rich was not compatible with the reaction conditions. The methodology was applied in a formal synthesis of Butoxycaine.

  • 28.
    Liu, Jianguo
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Asymmetric hydrogenation of allylic alcoholsusing iridium catalysts2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The first part of this thesis is focussed on the enantioselective iridium catalyzeda symmetric hydrogenation of allylic alcohols. The study involved the preparation of a range of allylic alcohols. These allylic alcohols were then hydrogenated, using iridium catalysts that have been previously prepared, to produce chiral alcohols with high yields and excellent enantioselectivity. The selectivity model of the reaction was used to accurately predict the absolute configuration of the hydrogenated products.

    The second part of the thesis was directed on the application of iridium catalyzed asymmetric hydrogenation of allylic alcohols in the synthesis of a late-stage intermediate of Aliskiren. A total of three synthetic routes were evaluated. The best synthesis relies on asymmetric hydrogenation of an allylic ester and an allylic alcohol as key-steps. Full conversion and 94% ee for the allylic alcohol were achieved. The late-stage intermediate of Aliskiren was successfully synthesized in eight steps.

  • 29.
    Lundberg, Helena
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Amidst the green Metal-catalyzed amide formation from carboxylic acids2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis describes novel methods for transition metal-catalyzed transformation of non-activated carboxylic acids to amides. It was found that 2-10 mol% of zirconium(IV) chloride or 10-20 mol% titanium(IV) isopropoxide catalyzed the formation of a range of secondary and tertiary amides in good to excellent yields (61-99%) in THF at 70-100°C, with molecular sieves present as water scavengers. The protocols proved to be suitable for gram scale preparation of amides, where a straight-forward work-up procedure was used for the isolation of the amide products. Furthermore, it was found that ammonium carbamates were suitable equivalents for gaseous ammonia and dimethylamine, in the group (IV) metal-catalyzed amidation of structurally different carboxylic acids, resulting in good to excellent yields (61-99%) of primary and N,N-dimethyl amides.

  • 30.
    Lundborg, Magnus
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Carbohydrate Structural Studies. Towards Automatic Structure Determination.2009Licentiate thesis, comprehensive summary (Other academic)
  • 31.
    Malmgren, Joel
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Unsymmetrical Diaryliodonium Salts: Development and Chemoselectivity studies2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The first part describes a chemoselectivity study on diaryliodonium salts where oxygen, nitrogen and carbon nucleophiles have been arylated. Twelve different unsymmetric phenyl(aryl)iodonium salts were designed with a systematic variation of the steric and electronic properties of the aryl group. The chemoselectivity varies greatly between the nucleophiles but several “dummy” aryl groups were identified where selective transfer of the phenyl moiety was consequently observed. HRMS studies of the salts revealed an interesting ligand exchange between the aryl groups of the iodine under certain conditions. This will aid the understanding of the mechanism operating in diaryliodonium salt arylation reactions. The results will facilitate the design of catalytic systems employing diaryliodonium salts, as well as help in search for applications with polymer-bound salts.

    The second part of the thesis describes the development of a new synthetic route towards unsymmetric diaryliodonium salts containing one heteroaryl moiety. The substrate scope of the facile one-pot protocol involves salts containing dummy groups with large steric bulk as well as electron-rich aryl groups. The utility of the salts are demonstrated in the arylation of both phenols and malonates where selective transfer of the heteroaryl moiety was consistently observed

  • 32.
    Manta, Bianca
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Quantum Chemical Studies of Enzymatic Reaction Mechanisms: Investigations of Cytosine Deaminase and ω-Transaminase2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis, density functional theory is used to study the reaction mechanisms of two dierent enzymes. Quantum chemical cluster models of the active sites were designed using available crystal structures. In this approach only the active site residues are considered and the effects of the surroundings are accounted for by a coordinate-locking scheme and a polarizable continuum model.

    The enzymes studied are cytosine deaminase (CDA) from Escherichia coli and ω-transaminase from Chromobacterium violaceum (Cv-ωTA). CDA is a zinc-dependentenzyme that catalyzes the hydrolytic deamination of cytosine into uracil and ammonia. Cv-ωTA carries out the interchange of amino and keto groups by utilizing the cofactor pyridoxal-5’-phosphate (PLP). The calculations provide optimized geometries and energies of transition states and intermediates, which are analyzed and used to construct a potential energy prole for the reaction and to identify the rate-limiting step. Each theoretical investigation provides a detailed description of the catalytic mechanism and establishes the roleof important active site residues.

    In the rst study (Paper I), it was found that a glutamate and an aspartate residue assist in the proton transfer events throughout the reaction. In the second study (Paper II), it was found that the lysine residue, which in the holo enzyme binds the cofactor PLP, assists in several proton transfer events once it has been replaced by the amino substrate. It was also found that the water substrate can be utilized as a proton shuttle before it is consumed at a later stage in the reaction mechanism.

    Apart from the detailed chemical insight, the results in this thesis confirmthat density functional theory together with cluster models of active sites is a very useful approach for studying diverse enzymatic reaction mechanisms.

  • 33.
    Nagendiran, Anuja
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Transition metal-catalysis: Applications of dynamic kinetic resolution in total synthesis and developments of novel methodologies using heterogeneous Pd catalysts2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The first part of the thesis describes a general and efficient route for the enantioselective synthesis of various α-substituted ketones and their corresponding lactones. The two key steps in this synthesis are the ruthenium and CALB-catalyzed dynamic kinetic resolution (DKR) which provided the exocyclic acetates in high yields and excellent enantioselectivity and the subsequent Cu-catalyzed α-allylic substitution giving the corresponding α-substituted products with inversed stereochemistry in high yields. This synthetic route was applied to the synthesis of the naturally occurring (R)-10-methyl-6-undecanolide, via subsequent oxidative cleavage and Baeyer-Villiger oxidation.

    In the second part, a new microwave-assisted methodology using a heterogeneous Pd nanocatalyst for Suzuki cross-couplings and hydrogenation of alkenes is presented. The catalytic system proved to be compatible with a wide range of functional groups and heteroatoms. In general, excellent yields were obtained within 45 min for the Suzuki cross-couplings and within 30 min for the hydrogenation reactions. The catalyst exhibited high recyclability with a low leaching in both cases.

    A novel method to prepare γ-alkylidene lactones from alkynoic acids mediated by a heterogeneous Pd(II) catalyst is described in the last part of the thesis. The protocol proved to be highly stereo- and regioselective, affording the 5-exo-dig lactone as the single product in all cases. In general, internal alkynes were cyclized in high to excellent yields within 3 hours using 0.3 mol% of catalyst loading. For internal alkynes, the catalyst loading had to be increased to 0.5 mol% along with prolonged reaction times and elevated temperatures in order to obtained high yields. The catalyst showed some recyclability with low leaching.

  • 34.
    Nilsson, Anna
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Identification and Syntheses of Semiochemicals Affecting Mnesampela privata and Trioza apicalis2009Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The Autumn gum moth, Mnesampela privata (Lepidoptera: Geometridae) is an endemic Australian moth whose larvae feed upon species of Eucalyptus. The moths favorite host plants are E. globulus and E. nitens which are the most important species used in commercial plantations of the Australian pulpwood industry. The autumn gum moth has become one of the most significant outbreak insects of eucalyptus plantations throughout Australia. As a consequence great financial losses to the forest industry occur. Today insecticides such as pyrethroids are used for control of eucalyptus defoliators as M. privata.

    The carrot psyllid, Trioza apicalis (Homoptera: Psylloidea), is one of the major pests of carrot (Daucus carota) in northern Europe. The psyllid causes curling of the carrot leafs and reduction of plant growth. Today the carrot crops are protected with the pyrethroid insecticide cypermethrin, which is toxic to aquatic organisms and is, from 2010, prohibited for use in Sweden by the Swedish Chemicals Inspectorate.

    An alternative to insecticides is to protect the seedlings with semiochemicals, a chemical substance or mixture of them that carries a message. This thesis describes the identification and the syntheses of semiochemicals from the above mentioned insect species.

    From analysis of abdominal tip extracts of M. privata females from Tasmania a blend of (3Z,6Z,9Z)-3,6,9-nonadecatriene and (3Z,6Z,9Z)-3,6,9-heneicosatriene was identified as the sex pheromone of this species. The identification of the C19- and C21-trienes was confirmed by synthesis.

    In the analysis of carrot leaf extracts we found a compound, α-cis-bergamotene, that induces antennal response in the carrot psyllid. This is just the beginning of the studies of trying to manipulate this psyllid with semiochemicals instead of insecticides.

  • 35.
    Nordin, Mikael
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Computational Studies of Transition Metal-Catalyzed Asymmetric Transfer Hydrogenation Reactions2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is based on two studies dealing with the computational investigation of asymmetric transfer hydrogenation reactions, in which hydrogen is transferred from a donor molecule (e.g. alcohol) to a substrate (ketone), via mediation of a metal-ligand catalyst complex. The catalysts, employing either rhodium or ruthenium in combination with pseudo-dipeptideligands, enantioselectively reduce acetophenone into the secondary alcohol. Stereochemically pure secondary alcohols are important intermediates in the synthesis of many pharmaceutical, agricultural and fine chemistry products. The demand for developing effective, mild and reproducible methods for making these alcohols is high.

    The present studies were made using density functional theory calculations, aiming at explaining the sources of enantioselectivity in the reactions. The calculations reproduce the trends in enantioselectivity quite satisfactorily. In the analysis of the obtained free energy graphs and the optimized geometries several factors that contribute to the enantioselectivity are identified

  • 36.
    Nygren, Patrik
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    De Novo Design and Characterization of Surface Binding Peptides - Steps toward Functional Surfaces2006Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The ability to create surfaces with well-defined chemical properties is a major research field. One possibility to do this is to design peptides that bind with a specific secondary structure to silica nanoparticles. The peptides discussed in this thesis are constructed to be random coil in solution, but are “forced” to become helical when adsorbed to the particles. The positively charged side-chains on the peptides strongly disfavor an ordered structure in solution due to electrostatic repulsion. When the peptides are introduced to the particles these charges will strongly favor the structure because of ion pair bonding between the peptide and the negatively charged nanoparticles. The peptide-nanoparticle system has been thoroughly investigated by systematic variations of the side-chains. In order to determine which factors that contributes to the induced structure, several peptides with different amino acid sequences have been synthesized. Factors that have been investigated include 1) the positive charge density, 2) distribution of positive charges, 3) negative charge density, 4) increasing hydrophobicity, 5) peptide length, and 6) by incorporating amino acids with different helix propensities. Moreover, pH dependence and the effect of different nanoparticle curvature have also been investigated. It will also be shown that the system can be modified to incorporate a catalytic site that is only active when the helix is formed. This research will increase our understanding of peptide-surface interactions and might be of importance for both nanotechnology and medicine.

  • 37.
    Pendrill, Robert
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Conformational studies of carbohydrates: MD simulation and NMR spectroscopy2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis describes various aspects of conformational studies of carbohydrates, from development of the methods by which experimental parameters are gathered to the application of NMR spectroscopy and MD simulation for the analysis of a disaccharide. Paper I describes the use of site-specific 13C labeling as a tool to resolve spectral overlap of 1H frequencies in a trisaccharide, allowing the measurement of important crossrelaxation rates and long-range couplings which were previously obscured. The newly acquired parameters are found to support the conformational equilibrium proposed in a previous study of the molecule. Paper II describes a problem in the J-HMBC experiment that occurs when there are large homonuclear 13C scalar couplings present, a situation typically occurring when studying labeled compounds. By introducing a constant-time element to the pulse-program, the interference by one-bond homonuclear 1JC,C couplings is shown to be suppressed when applied to site-specifically labeled disaccharides. The last project, paper III, concerns the conformation and dynamics of the disaccharide β-L-Fucp-(1→6)-α-D-Glcp-OMe, showing the difficulties associated with the flexible nature of (1→6) linkages. The molecule is found to have significant flexiblity in both the ω and ψ torsions. A three-state equilibrium is found for ω, while ψ has two states connected by a low barrier. The force field parm22/SU01 is able to reproduce and explain the experimental parameters reasonably well, but it is concluded that some of the states have slightly incorrect torsion angles and that the populations are not correctly represented.

  • 38.
    Pershagen, Elias
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Development and applications of lanthanide-based luminescent probes2012Licentiate thesis, comprehensive summary (Other academic)
  • 39.
    Persson, Andreas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium(II)-catalyzed carbocyclizations. Moving from enallenes to aza-enallenes.2010Licentiate thesis, comprehensive summary (Other academic)
  • 40.
    Pu, Maoping
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Dynamical Analysis of Chemical Activity of Sterically Encumbered Lewis acid/base Pairs2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This licentiate thesis is about the dynamics analysis of chemical reactions involving a stoichiometric mixture of sterically hindered Lewis base (LB) and Lewis acid (LA) – the so-called frustrated Lewis pairs (FLPs). The tool for dynamical description of chemical reactions is the ab initio molecular dynamics (AIMD) simulations together with the calculation of minimum energy paths (MEPs) on the potential energy surfaces (PESs). The aim is to take into account both the interatomic forces, computed with the dispersion-corrected density functional theory, and the motion of the atoms at finite (non-zero) temperature. With extensive AIMD/PES simulations, we have exposed and explained transition state theory (TST)/MEP paradigm failures for such important chemical reactions as binding (sequestration) of CO2 and the heterolytic cleavage of H2 by a Lewis base, tBu3P, and a Lewis acid, B(C6F5)3. The insight into dynamical aspects of FLP activity, obtained from a synergistic combination of AIMD and PES calculations, is the basis for qualitative and quantitative predictions which could be useful for future experiments

  • 41.
    Rabten, Wangchuk
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Development of Ruthenium Complexes for Water Oxidation2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Development of a methodology to combat the world energy crisis can be one of the greatest challenges now facing mankind. Our research is focused on the development of versatile catalysts (WOCs) that oxidize water into molecular oxygen at neutral pH, driven by the mild one-electron oxidant [Ru(bpy)3]3+, using natural photosynthesis a sa model.

    The first part of the thesis describes the unexpected generation of a mononuclear Ru complex from a hexadentate ligand, which was envisioned to accommodate two metal atoms. The study of this mononuclear catalyst clearly demonstrated the importance of having strongly electron donating functional groups and their effect on catalytic water oxidation.

    The second part of thesis presents the preparation of a mononuclear Ru complex, which contains two amide groups in the ligand scaffold and the superior reactivity of this complex in catalytic water oxidation under neutral condition. When mild one-electronoxidant [Ru(bpy)3]3+ was employed, TONs of ∼ 6000 and TOFs of ∼20s-1 were achieved, which are the highest values reported so far, using this type of oxidant

  • 42.
    Rönnols, Jerk
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of oligosaccharides and conformational analysis by NMR spectroscopy2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The first part of this thesis describes investigations of the conformations of six N-linked pseudodisaccharides (Paper I), which were synthesized as glycosidase inhibitor candidates, and 10 β-D-xylopyranoside derivatives bearing hydrophobic aglycons (Paper II), by NMR spectroscopic methods. In paper I the ring conformations of 2- and 3-amino-α-D-altropyranosides, and ω torsions of altrosides, glucosides and mannosides were described, in neutral and protonated states. Occurrences of the conformations 4C1, oS2 and 1C4 were found for the altrosides, with large differences from the neutral to charged state observed for the 2-linked structures.

    The studied xylosides were found to predominantly reside in 4C1 conformation, with some population of 2So (˜5%), with exception of a 3-deoxygenated compound, which was found to be in equilibrium between the 4C1 and 1C4 conformations, and two epimerized compounds. The 3-deoxy compound was studied in further detail. The equilibrium was found to differ with temperature, and an estimate of the activation energy is presented.

    The second part describes synthesis towards N-glycan oligosaccharides with various fucosylation patterns. The synthesis involves a safe route to a glycosyl azide, a high-yielding conversion of the azide to acetyl amide and a stereoselective β-mannosylation performed by preactivation of the mannosyl donor. The synthesis of an orthogonally protected core trisaccharide is described.

  • 43.
    Selander, Nicklas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Development of Multi-Component Reactions using Catalytically Generated Allyl Metal Reagents2008Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This licentiate thesis is based on the development of catalytic reactions for the synthesis and application of organometallic reagents. By use of palladium pincer-complex catalysts, we have developed an efficient procedure for the synthesis of allylboronates starting from allylic alcohols. These reactions were further extended by including various one-pot multi-component reactions, using the in situ generated allylboronates. Furthermore, novel unsymmetrical palladium pincer-complexes were synthesized and studied in auto-tandem catalysis.

  • 44.
    Slagbrand, Tove
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ruthenium-Catalyzed Asymmetric Transfer Hydrogenation2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis covers the development of two new methods for the asymmetric reduction of ketones and ketone intermediates. The protocols developed are based on the use of a ruthenium pseudo-dipeptide catalyst that previously has been shown to be efficient and selective in the asymmetric reduction of carbonyl compounds.

    The first part of this thesis describes the development of an efficient protocol for sequential isomerization and asymmetric reduction of allylic alcohols into saturated chiral alcohols in a one-pot procedure. This transformation has previously been reported at high temperature and with long reaction times, yielding the products in poor enantioselectivity. In the current project, the same transformation was investigated, however, with a significally more active catalyst. As a result we were able to use milder reaction conditions which yielded higher enantioselectivity in comparison to previously published protocols. The scope was investigated and the mechanism was briefly studied.

    The second part of this thesis describes the asymmetric reduction of sterically demanding ketones with the same metal complex as in the first part. It was found that longer reaction times in combination with the use of potassium tert-butoxide facilitate the reduction of sterically hindered ketones, to yield secondary alcohols with high enantioselectivity. The scope and the role of potassium were investigated, and a plausible new transition state was postulated.

  • 45.
    Steen, Robert
    Mälardalen University, Department of Biology and Chemical Engineering.
    The Synthesis of Molecular Switches Based Upon Ru(II) Polypyridyl Architecture for Electronic Applications2007Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    According to the famous axiom known as Moore’s Law the number of transistors that can be etched on a given piece of silicon, and therefore the computing power, will double every 18 to 24 months. For the last 40 years Moore’s prediction has held true as computers have grown more and more powerful. However, around 2020 hardware manufac-turers will have reached the physical limits of silicon. A proposed solution to this dilemma is molecular electronics. Within this field researchers are attempting to develop individual organic molecules and metal complexes that can act as molecular equivalents of electronic components such as diodes, transistors and capacitors. By utilizing molecular electronics to construct the next generation of computers processors with 100,000 times as many components on the same surface area could potentially be created.

    We have synthesized a range of new pyridyl thienopyridine ligands and compared the electrochemical and photophysical properties of their corresponding Ru(II) complexes with that with the Ru(II) complexes of a variety of ligands based on 6-thiophen-2-yl-2,2´-bipyridine and 4-thiophen-2-yl-2,2´-bipyridine. While the electrochemistry of the Ru(II) complexes were similar to that of unsubstituted [Ru(bpy)3]2+, substantial differences in luminescence lifetimes were found. Our findings show that, due to steric interactions with the auxiliary bipy-ridyl ligands, luminescence is quenched in Ru(II) complexes that in-corporate the 6-thiophen-2-yl-2,2´-bipyridine motif, while it is on par with the luminescence of [Ru(bpy)3]2+ in the Ru(II) complexes of the pyridyl thienopyridine ligands. The luminescence of the Ru(II) com-plexes based on the 4-thiophen-2-yl-2,2´-bipyridine motif was en-hanced compared to [Ru(bpy)3]2+ which indicates that complexes of this category are the most favourable for energy/electron-transfer sys-tems.

    At the core of molecular electronics are the search for molecular ON/OFF switches. We have synthesized a reversible double cyclome-tallated switch based on the Ru(tpy) complex of 3,8-bis-(6-thiophen-2-yl-pyridin-2-yl)-[4,7]phenanthroline. Upon treatment with acid/base the complex can be switched between the cyclometallated and the S-bonded form. This prototype has potentially three different states which opens the path to systems based on ternary computer logic.

  • 46.
    Stridfeldt, Elin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Metal‐Free Arylations of Oxygen and Nitrogen Nucleophiles: Applications of Diaryliodonium Salts2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis concerns development of new methods for metal‐free arylations in organic synthesis. The protocols discussed in the thesis are based on a class of hypervalent iodine compounds called diaryliodonium salts. These reagents are known to transfer aryl moieties to suitable nucleophiles.

    The first part describes O‐arylation of ethyl acetohydroxamate, which serves as a hydroxylamine equivalent. Electron‐rich as well as electron‐poor aryl groups could be transferred from the diaryliodonium salts. The arylation products could then be used as intermediates in a straightforward meta‐free one‐pot synthesis of benzofurans. Using this procedure, various substituted benzofurans were obtained in good yields. Furthermore, this methodology was used to synthesise the natural product Stemofuran A in one single step, starting from commercially available compounds. Three formal syntheses of other bioactive benzofurans were included.

    The second part describes N‐arylation of secondary acyclic amides. The chemoselectivity was explored with unsymmetric diaryliodonium salts, and aryl moieties with ortho‐substituents were preferably transferred. The protocol was suitable for electron‐deficient as well as highly sterically congested diaryliodonium salts. The transfer of electron‐rich aryl moieties was problematic. However, the reactivity for the amide was complementary to that of the salts and electron‐rich amides were phenylated in high yields. Furthermore, the protocol was compatible with benzamides and amides having sterically hindered acyl groups.

    Both arylation protocols discussed in this thesis work at ambient temperature and a variety of counter‐ions of the diaryliodonium salts were tolerated.

  • 47.
    Svensson, Mona
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Structure elucidation of O-antigen polysaccharides from Escherichia coli2010Licentiate thesis, comprehensive summary (Other academic)
  • 48.
    Tinnis, Fredrik
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Selective Transition Metal Catalyzed Transformations – Reductions and Amidations2012Licentiate thesis, comprehensive summary (Other academic)
  • 49.
    Torssell, Staffan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Amino Aacohols: stereoselective synthesis and applications in diversity-oriented synthesis2005Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis is divided into three separate parts with amino alcohols as the common feature. The first part describes the development of a novel three-component approach to the synthesis of α-hydroxy-β-amino esters. Utilizing a highly diastereoselective Rh(II)-catalyzed 1,3-dipolar cycloaddition of carbonyl ylides to various aldimines, syn-α-hydroxy-β-amino esters formed in high yields and excellent diastereoselectivities. This methodology was also applied in a short enantioselective synthesis of the C-13 side-chain of Taxol.

    The second part of the thesis describes a total synthesis of D-erythro- Sphingosine based on a cross-metathesis approach to assemble the polar head group and the aliphatic chain.

    The last part deals with the application of amino alcohols as scaffolds in a diversity-oriented protocol for the development of libraries of small polycyclic molecules. The design of the libraries is based on the iterative use of two powerful ring-forming reactions; a ring-closing metathesis and an intramolecular Diels-Alder reaction, to simultaneously introduce structural complexity and diversity.

  • 50.
    Träff, Annika
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Dynamic Kinetic Resolution. A Tool for Bringing Bioorganic and Organometallic Chemistry together.2009Licentiate thesis, comprehensive summary (Other academic)
12 1 - 50 of 55
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf