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  • 101.
    Lindstedt, Erik
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ghosh, Raju
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Metal-Free Synthesis of Aryl Ethers in Water2013In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 15, no 23, p. 6070-6073Article in journal (Refereed)
    Abstract [en]

    The first arylation of allylic and benzylic alcohols with diaryliodonium salts is reported. The reaction yields alkyl aryl ethers under mild and metal-free conditions. Phenols are arylated to diaryl ethers in good to excellent yields. The reaction employs diaryliodonium salts and sodium hydroxide in water at low temperature, and excess amounts of the coupling partners are avoided.

  • 102.
    Lindstedt, Erik
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Reitti, Marcus
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    One-Pot Synthesis of Unsymmetric Diaryliodonium Salts from Iodine and Arenes2017In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 82, no 22, p. 11909-11914Article in journal (Refereed)
    Abstract [en]

    The first synthesis of unsymmetric diaryliodonium salts directly from iodine and arenes is presented. The methodology provides diaryliodonium salts with the trimethoxyphenyl (TMP) moiety as dummy group. The protocol avoids the customary use of iodoarenes, which can be both expensive and toxic. Excess reagents are not required, and the reactions are performed under mild conditions. O-Arylations with these TMP salts were demonstrated to be highly chemoselective.

  • 103.
    Lindstedt, Erik
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Stridfeldt, Elin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mild Synthesis of Sterically Congested Alkyl Aryl Ethers2016In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 18, no 17, p. 4234-4237Article in journal (Refereed)
    Abstract [en]

    An efficient and transition-metal-free method is presented to access tertiary alkyl aryl ethers by arylation of tertiary alcohols with ortho-substituted diaryliodonium salts. The scope covers cyclic and acyclic aliphatic, benzylic, allylic, and propargylic tertiary alcohols as well as primary and secondary fluorinated alcohols. The methodology gives access to alkyl aryl ethers of previously unprecedented steric congestion. Furthermore, the versatility of the developed procedure was demonstrated by arylation of the pro-drug mestranol.

  • 104.
    Lindström, Ulf M.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Somfai, Peter
    Microwave-assisted aminolysis of vinylepoxides1999In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 40, no 52, p. 9273-9276Article in journal (Refereed)
    Abstract [en]

    Di- and trisubstituted vinyl epoxides in NH4OH were subjected to microwave irradn. affording the corresponding vicinal amino alcs. in high yields. The reaction is stereospecific and highly regioselective for addn. at the allylic carbon. [on SciFinder(R)]

  • 105.
    Lindén, Auri
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Flavins as Biomimetic Catalysts for Sulfoxidation by H2O2: Catalyst Immobilization in Ionic Liquid for H2O2 Oxidations2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    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.

    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.

    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)2 or methyl trioxorhenium (MTO) as co-catalysts together with the substrate-selective osmium catalyst. Good to excellent yields of the diols were obtained.

  • 106.
    Liu, Jianguo
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Iridium Catalysed Asymmetric Hydrogenation of Olefins and Dynamic Kinetic Resolution in the Asymmetric Hydrogenation of Allylic Alcohols2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    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 (>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. 

  • 107.
    Lundberg, Helena
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Group (IV) Metal-Catalyzed Direct Amidation: Synthesis and Mechanistic Considerations2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The amide unit constitutes the backbone of proteins, and it is present in a large number of pharmaceutically active molecules, polymeric materials such as nylon and Kevlar, as well as in food additives like aspartame. Amides are produced in enormous amounts every year, thus, environmentally friendly and selective methods for their formation are of great importance. This thesis deals with the direct formation of amides from non-activated carboxylic acids and amines with the aid of group (IV) metal complexes. Water is the only by-product of this environmentally benign process. This fact stands in contrast to the most common methods for amide formation to date, which involve the use of waste-intensive, expensive and often toxic coupling reagents. The catalytic protocols presented herein use titanium, zirconium and hafnium complexes under mild reaction conditions to produce amides in good to excellent yields. Furthermore, carbamates are demonstrated to be suitable sources of gaseous amines for the formation of primary and tertiary amides under catalytic conditions. In addition, preliminary results from on-going mechanistic investigations of the zirconium- and hafnium-catalyzed processes are presented.

  • 108.
    Lundberg, Helena
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Tinnis, Fredrik
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Selander, Nicklas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Adolfsson, Hans
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Catalytic amide formation from non-activated carboxylic acids and amines2014In: Chemical Society Reviews, ISSN 0306-0012, E-ISSN 1460-4744, Vol. 43, no 8, p. 2714-2742Article, review/survey (Refereed)
    Abstract [en]

    The amide functionality is found in a wide variety of biological and synthetic structures such as proteins, polymers, pesticides and pharmaceuticals. Due to the fact that synthetic amides are still mainly produced by the aid of coupling reagents with poor atom-economy, the direct catalytic formation of amides from carboxylic acids and amines has become a field of emerging importance. A general, efficient and selective catalytic method for this transformation would meet well with the increasing demands for green chemistry procedures. This review covers catalytic and synthetically relevant methods for direct condensation of carboxylic acids and amines. A comprehensive overview of homogeneous and heterogeneous catalytic methods is presented, covering biocatalysts, Lewis acid catalysts based on boron and metals as well an assortment of other types of catalysts.

  • 109.
    Lundborg, Magnus
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Computer-Assisted Carbohydrate Structural Studies and Drug Discovery2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Carbohydrates are abundant in nature and have functions ranging from energy storage to acting as structural components. Analysis of carbohydrate structures is important and can be used for, for instance, clinical diagnosis of diseases as well as in bacterial studies. The complexity of glycans makes it difficult to determine their structures. NMR spectroscopy is an advanced method that can be used to examine carbohydrates at the atomic level, but full assignments of the signals require much work. Reliable automation of this process would be of great help. Herein studies of Escherichia coli O-antigen polysaccharides are presented, both a structure determination by NMR and also research on glycosyltransferases which assemble the polysaccharides. The computer program CASPER has been improved to assist in carbohydrate studies and in the long run make it possible to automatically determine structures based only on NMR data.

    Detailed computer studies of glycans can shed light on their interactions with proteins and help find inhibitors to prevent unwanted binding. The WaaG glycosyltransferase is important for the formation of E. coli lipopolysaccharides. Molecular docking analyses of structures confirmed to bind this enzyme have provided information on how inhibitors could be composed. Noroviruses cause gastroenteritis, such as the winter vomiting disease, after binding human histo-blood group antigens. In one of the projects, fragment-based docking, followed by molecular dynamics simulations and binding free energy calculations, was used to find competitive binders to the P domain of the capsid of the norovirus VA387. These novel structures have high affinity and are a very good starting point for developing drugs against noroviruses. The protein targets in these two projects are carbohydrate binding, but the techniques are general and can be applied to other research projects.

  • 110. Mally, Manuela
    et al.
    Fontana, Carolina
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    LeibundGut-Landmann, Salome
    Laacisse, Lamia
    Fan, Yao-Yun
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Aebi, Markus
    Glycoengineering of host mimicking type-2 LacNAc polymersand Lewis X antigens on bacterial cell surfaces2013In: Molecular Microbiology, ISSN 0950-382X, E-ISSN 1365-2958, Vol. 87, no 1, p. 112-131Article in journal (Refereed)
    Abstract [en]

    Bacterial carbohydrate structures play a central role in mediating a variety of host-pathogen interactions. Glycans can either elicit protective immune response or lead to escape of immune surveillance by mimicking host structures. Lipopolysaccharide (LPS), a major component on the surface of Gram-negative bacteria, is composed of a lipid A-core and the O-antigen polysaccharide. Pathogens like Neisseria meningitidis expose a lipooligosaccharide (LOS), which outermost glycans mimick mammalian epitopes to avoid immune recognition. Lewis X (Gal beta 1-4(Fuc alpha 1-3)GlcNAc) antigens of Helicobacter pylori or of the helminth Schistosoma mansoni modulate the immune response by interacting with receptors on human dendritic cells. In a glycoengineering approach we generate human carbohydrate structures on the surface of recombinant Gram-negative bacteria, such as Escherichia coli and Salmonella enterica sv. Typhimurium that lack O-antigen. A ubiquitous building block in mammalian N-linked protein glycans is Gal beta 1-4GlcNAc, referred to as a type-2 N-acetyllactosamine, LacNAc, sequence. Strains displaying polymeric LacNAc were generated by introducing a combination of glycosyltransferases that act on modified lipid A-cores, resulting in efficient expression of the carbohydrate epitope on bacterial cell surfaces. The poly-LacNAc scaffold was used as an acceptor for fucosylation leading to polymers of Lewis X antigens. We analysed the distribution of the carbohydrate epitopes by FACS, microscopy and ELISA and confirmed engineered LOS containing LacNAc and Lewis X repeats by MALDI-TOF and NMR analysis. Glycoengineered LOS induced pro-inflammatory response in murine dendritic cells. These bacterial strains can thus serve as tools to analyse the role of defined carbohydrate structures in different biological processes.

  • 111.
    Malmgren, Joel
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Iodonium Salts: Preparation, Chemoselectivity and Metal-Catalyzed Applications2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis concerns the preparation and use of diaryliodonium salts. In Project I various unsymmetrical diaryliodonium salts were reacted with three different nucleophiles in order to study the chemoselectivity of the reactions of the salts. The main focus of this project was to gain a deeper understanding of the underlying factors that affect the chemoselectivity in transition metal-free arylation reactions. They were found to be very nucleophile-dependent. Some nucleophiles were very sensitive to electronic effects, whereas others were sensitive to steric factors. Ultimately, some arenes are never transferred. A very interesting scrambling reaction was also observed under the reaction conditions, where unsymmetrical diaryliodonium salts form symmetrical salts in situ.

    Project II details the preparation of N-heteroaryliodonium salts via a one-pot procedure. The salts were designed so that the N-heteroaryl moiety was selectively transferred in applications both with and without transition metals. The chemoselectivity was demonstrated by selective transfer of the pyridyl group onto two different nucleophiles.

    The third project in the thesis discusses the synthesis of alkynyl(aryl)iodonium salts and alkynylbenziodoxolones from arylsilanes. This protocol could potentially be a very useful complement to the existing procedures, in which boronic acids are used.

    The last part of the thesis (Project IV) describes a C-2 selective arylation of indoles where diaryliodonium salts were used in combination with hetero-geneous palladium catalysis. This transformation was performed in water at ambient temperature to 50 °C, and tolerated variations of both the indole and the diaryliodonium salt. Importantly, several N-H indoles could be arylated. The MCF-supported Pd-catalyst showed very little leaching and it was demonstrated that the main part of the reaction occurred via heterogeneous catalysis.

  • 112.
    Malmgren, Joel
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nagendiran, Anuja
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    C-2 Selective Arylation of Indoles with Heterogeneous Nanopalladium and Diaryliodonium Salts2014In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 20, no 42, p. 13531-13535Article in journal (Refereed)
    Abstract [en]

    A simple and efficient method to prepare synthetically useful 2-arylindoles is presented, using a heterogeneous Pd catalyst and diaryliodonium salts in water under mild conditions. A remarkably low leaching of metal catalyst was observed under the applied conditions. The developed protocol is highly C-2 selective and tolerates structural variations both in the indole and in the diaryliodonium salt. Arylations of both NH indoles and N-protected indoles with ortho-substituted, electron-rich, electron-deficient, or halogenated diaryliodonium salts were achieved to give the desired products in high to excellent isolated yields within 6 to 15 h at room temperature or 40 °C.

  • 113.
    Malmgren, Joel
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Santoro, Stefano
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Jalalian, Nazli
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Himo, Fahmi
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Arylation with Unsymmetrical Diaryliodonium Salts: A Chemoselectivity Study2013In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 19, no 31, p. 10334-10342Article in journal (Refereed)
    Abstract [en]

    Phenols, anilines, and malonates have been arylated under metal-free conditions with twelve aryl(phenyl)iodonium salts in a systematic chemoselectivity study. A new “anti-ortho effect” has been identified in the arylation of malonates. Several “dummy groups” have been found that give complete chemoselectivity in the transfer of the phenyl moiety, irrespective of the nucleophile. An aryl exchange in the diaryliodonium salts has been observed under certain arylation conditions. DFT calculations have been performed to investigate the reaction mechanism and to elucidate the origins of the observed selectivities. These results are expected to facilitate the design of chiral diaryliodonium salts and the development of catalytic arylation reactions that are based on these sustainable and metal-free reagents.

  • 114.
    Manta, Bianca
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Quantum Chemical Studies of Enzymatic Reaction Mechanisms2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Computer modeling of enzymes is a valuable complement to experiments. Quantum chemical studies of enzymatic reactions can provide a detailed description of the reaction mechanism and elucidate the roles of various residues in the active site. Different reaction pathways can be analyzed, and their feasibility be established based on calculated energy barriers.

    In the present thesis, density functional theory has been used to study the active sites and reaction mechanisms of three different enzymes, cytosine deaminase (CDA) from Escherichia coli, ω-transaminase from Chromobacterium violaceum (Cv-ωTA) and dinitrogenase reductase-activating glycohydrolase (DraG) from Rhodospirillum rubrum. The cluster approach has been employed to design models of the active sites based on available crystal structures. The geometries and energies of transition states and intermediates along various reaction pathways have been calculated, and used to construct the energy graphs of the reactions.

    In the study of CDA (Paper I), two different tautomers of a histidine residue were considered. The obtained reaction mechanism was found to support the main features of the previously proposed mechanism. The sequence of the events was established, and the residues needed for the proton transfer steps were elucidated.

    In the study of Cv-ωTA (Paper II and Paper III), two active site models were employed to study the conversion of two different substrates, a hydrophobic amine and an amino acid. Differences and similarities in the reaction mechanisms of the two substrates were established, and the role of an arginine residue in the dual substrate recognition was confirmed.

    In the study of DraG (Paper IV), two different substrate-binding modes and two different protonation states of an aspartate residue were considered. The coordination of the first-shell ligands and the substrate to the two manganese ions in the active site was characterized, and a possible proton donor in the first step of the proposed reaction mechanism was identified.

  • 115.
    Marcos, Rocio
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martín-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Combined Enzyme and Transition-Metal Catalysis for Dynamic Kinetic Resolutions2012In: Israel Journal of Chemistry, ISSN 0021-2148, Vol. 52, no 7, p. 639-652Article, review/survey (Refereed)
    Abstract [en]

    The preparation of optically pure alcohols, axially chiral allenes, and amine derivatives by using enzymes and transition-metal catalysts through dynamic kinetic resolution (DKR) is reviewed. After a general introduction into enzymatic kinetic resolutions and racemizations catalyzed by transition-metal complexes, selected examples of DKRs are presented, from early work to more recent outstanding contributions, and also applications of this approach.

  • 116.
    Martinez-Erro, Samuel
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sanz-Marco, Amparo
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Gómez, Antonio Bermejo
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Vazquez-Romero, Ana
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ahlquist, Mårten S. G.
    Martin-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Base-Catalyzed Stereospecific Isomerization of Electron-Deficient Allylic Alcohols and Ethers through Ion-Pairing2016In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 138, no 40, p. 13408-13414Article in journal (Refereed)
    Abstract [en]

    A mild base-catalyzed strategy for the isomerization of allylic alcohols and allylic ethers has been developed. Experimental and computational investigations indicate that transition metal catalysts are not required when basic additives are present. As in the case of using transition metals under basic conditions, the isomerization catalyzed solely by base also follows a stereospecific pathway. The reaction is initiated by a rate-limiting deprotonation. Formation of an intimate ion pair between an allylic anion and the conjugate acid of the base results in efficient transfer of chirality. Through this mechanism, stereochemical information contained in the allylic alcohols is transferred to the ketone products. The stereospecific isomerization is also applicable for the first time to allylic ethers, yielding synthetically valuable enantioenriched (up to 97% ee) enol ethers.

  • 117. Mensch, Carl
    et al.
    Pendrill, Robert
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johannessen, Christian
    Studying the Glycan Moiety of RNase B by Means of Raman and Raman Optical Activity2014In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 15, no 11, p. 2252-2254Article in journal (Refereed)
    Abstract [en]

    Raman and Raman optical activity (ROA) spectroscopy are used to study the solution-phase structure of the glycan moiety of the protein ribonuclease B (RNase B). Spectral data of the intact glycan moiety of RNase B is obtained by subtracting high-quality spectral data of RNase A, the non-glycosylated form of the RNase, from the spectra of the glycoprotein. The remaining difference spectra are compared to spectra generated from Raman and ROA data of the constituent disaccharides of the RNase glycan, achieving convincing spectral overlap. The results show that ROA spectroscopy is able to extract detailed spectral data of the glycan moieties of proteins, provided that the non-glycosylated isoform is available. Furthermore, good comparison between the full glycan spectrum and the regenerated spectra based on the disaccharide data lends great promise to ROA as a tool for the solution-phase structural analysis of this structurally elusive class of biomolecules.

  • 118.
    Merritt, Eleanor A.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Malmgren, Joel
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Klinke, Felix J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of diaryliodonium triflates using environmentally benign oxidizing agents2009In: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry, ISSN 0936-5214, E-ISSN 1437-2096, no 14, p. 2277-2280Article in journal (Refereed)
  • 119.
    Merritt, Eleanor A.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    α-Functionalization of carbonyl compounds using hypervalent iodine reagents2011In: Synthesis (Stuttgart), ISSN 0039-7881, E-ISSN 1437-210X, no 4, p. 517-538Article in journal (Refereed)
    Abstract [en]

    α-Functionalized carbonyl compounds are versatile intermediates in organic synthesis. A broad range of both carbon and heteroatom substituents can be introduced into the α-position of carbonyl compounds using hypervalent iodine reagents. Herein we summarize the use of these environmentally benign reagents with particular emphasis on catalytic and asymmetric methodology developed over the past decade.

  • 120.
    Moa, Sara
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Quantum chemical modelling of enantioselectivity in alcohol dehydrogenase2017Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Biocatalytic methods of synthesis are becoming increasingly important in industry. Using enzymes as catalysts allows highly selective reactions to be performed under milder physical conditions and in a more environmentally benign fashion than most corresponding chemical catalysts.

    Enzymes have in general evolved to perform one type of reaction on a limited set of molecules, and hence there is often a need to alter the specificity of an enzyme to suit a desired process. Understanding the details of enzymatic catalysis at a quantum mechanical level enables the intelligent redesign of these macromolecules. For this purpose, density functional theory (DFT) has been shown to epitomise a suitable balance of accuracy and computational cost. Thus, this thesis describes the quantum chemical rationalisation of the reaction mechanism and sources of selectivity of the bacterial alcohol dehydrogenase TbSADH – an enzyme highly suited to modification for industrial processes.

    ADHs catalyse reversibly the interconversion of alcohols and ketones or aldehydes. Herein, the general ADH reaction mechanism was shown to be viable for this enzyme. In addition, the experimental enantiopreference of the enzyme was reproduced, and thus the reversal of selectivity seen with the slight increase in substrate size was captured. The main determinant of selectivity was found to be a fine balance of repulsive steric interactions and attractive dispersion effects between the substrate and the hydrophobic binding pockets. The ability of the modelling methodology to capture effects such as these represents further evidence of its usefulness as a complement to experimental work in designing the biocatalysts of the future.

    The development of protocols to allow quantum mechanical investigation of the production of large and industrially interesting axially chiral alcohols is also presented. The work described has showed that quantum chemical models of many hundreds of atoms are now within our grasp, and although they were unable to correctly describe the selectivity for the large 4-(bromomethylene)cyclohexan-1-one in TbSADH, the protocols devised can be very useful for future investigations of enzymatic catalysis.

  • 121.
    Nagendiran, Anuja
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Catalytic reactions with palladium supported on mesocellular foam: Applications in hydrogenation, isomerization, and C-C bond forming reactions2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The major part of this thesis concerns the development of catalytic methodologies based on palladium nanoparticles immobilized on aminopropyl-functionalized siliceous mesocellular foam (Pd0-AmP-MCF). The catalytic activity of the precursor to the nanocatalyst, PdII-AmP-MCF is also covered by this work.

    In the first part the application of Pd0-AmP-MCF in Suzuki-Miyaura cross-coupling reactions and transfer hydrogenation of alkenes under microwave irradiation is described. Excellent reactivity was observed and a broad range of substrates were tolerated for both transformations. The Pd0-AmP-MCF exhibited high recyclability as well as low metal leaching in both cases.

    The aim of the second part was to evaluate the catalytic efficiency of the closely related PdII-AmP-MCF for cycloisomerization of various acetylenic acids. The catalyst was able to promote formation of lactones under mild conditions using catalyst loadings of 0.3 - 0.5 mol% at temperatures of up to 50 oC in the presence of Et3N. By adding 1,4-benzoquinone to the reaction, the catalyst could be recycled four times without any observable decrease in the activity.

    The selective arylation of indoles at the C-2 position using Pd-AmP-MCF and symmetric diaryliodonium salts is presented in the third part. These studies revealed that Pd0-AmP-MCF was more effective than PdII-AmP-MCF for this transformation. Variously substituted indoles as well as diaryliodonium salts were tolerated, giving arylated indoles in high yields within 15 h at 20 - 50 oC in H2O. Only very small amounts of Pd leaching were observed and in this case the catalyst exhibited moderate recyclability.

    The final part of the thesis describes the selective hydrogenation of the C=C in different α,β-unsaturated systems. The double bond was efficiently hydrogenated in high yields both under batch and continuous-flow conditions. High recyclability and low metal leaching were observed in both cases.

  • 122.
    Nagendiran, Anuja
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Pascanu, Vlad
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bermejo Gómez, Antonio
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    González Miera, Greco
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Verho, Oscar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martín-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mild and Selective Catalytic Hydrogenation of the C=C Bond in a,b-Unsaturated Carbonyl Compounds Using Supported Palladium Nanoparticles2016In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 22, no 21, p. 7184-7189Article in journal (Refereed)
    Abstract [en]

    Chemoselective reduction of the C=C bond in a variety of α,β-unsaturated carbonyl compounds using supported palladium nanoparticles is reported. Three different heterogeneous catalysts were compared using 1 atm of H2: 1) nano-Pd on a metal–organic framework (MOF: Pd0-MIL-101-NH2(Cr)), 2) nano-Pd on a siliceous mesocellular foam (MCF: Pd0-AmP-MCF), and 3) commercially available palladium on carbon (Pd/C). Initial studies showed that the Pd@MOF and Pd@MCF nanocatalysts were superior in activity and selectivity compared to commercial Pd/C. Both Pd0-MIL-101-NH2(Cr) and Pd0-AmP-MCF were capable of delivering the desired products in very short reaction times (10–90 min) with low loadings of Pd (0.5–1 mol %). Additionally, the two catalytic systems exhibited high recyclability and very low levels of metal leaching.

  • 123.
    Nagendiran, Anuja
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Verho, Oscar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Haller, Clemence
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Cycloisomerization of Acetylenic Acids to gamma-Alkylidene Lactones using a Palladium(II) Catalyst Supported on Amino-Functionalized Siliceous Mesocellular Foam2014In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 79, no 3, p. 1399-1405Article in journal (Refereed)
    Abstract [en]

    Cycloisomerization of various gamma-acetylenic acids to their corresponding gamma-alkylidene lactones by the use of a heterogeneous Pd(II) catalyst supported on amino-functionalized siliceous mesocellular foam is described. Substrates containing terminal as well as internal alkynes were cyclized in high to excellent yields within 2-24 h under mild reaction conditions. The protocol exhibited high regio- and stereoselectivity, favoring the exo-dig product with high Z selectivity. Moreover, the catalyst displayed excellent stability under the employed reaction conditions, as demonstrated by its good recyclability and low leaching.

  • 124.
    Nilsson, Johan
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Studies on Oxidative Couplings in H-Phosphonate Chemistry2004Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis oxidative coupling of H-phosphonate and H phosphonothioate diesters with different alcohols and amines are presented. Since the reactions with alcohols previously have been particularly unfavourable due to competing side reactions, a modified protocol leading to high coupling yields of structurally diverse hydroxylic components was developed. The phosphorylation reaction was studied using 31P NMR spectroscopy and for the first time the previously only postulated reactive intermediate involved in these reactions was observed.

    The use of iodine in combination with a bulky chlorosilane in pyridine was found to have a profound effect on both the suppression of side reactions and the rate of the oxidative couplings, and led to a clean formation of phosphorylated products in high yields. This synthetic protocol was then extended to include coupling reactions with bis-functional reagents containing hexamethylene linkers to provide handles for derivatisations of oligonucleotides.

    A synthetic protocol consisting of the stereospecific oxidative coupling of amines with H-phosphonate diesters to produce phosphoroamidates was designed in such a way that it permitted control of the stereochemical outcome of the reactions.

    Based on a silylation-mediated reaction utilising phenyl H phosphonothioate monoester as a thiophosphonyl transferring agent, a method was developed and used for the preparation of H-phosphonothioate building blocks for the synthesis of DNA analogues.

  • 125.
    Nordmark, Eva-Lisa
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Structural and Interaction Studies of Bacterial Polysaccharides by NMR Spectroscopy2004Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    An introduction to bacterial polysaccharides and the methods for structural determination are described in the first two parts of the thesis.

    In a structural elucidation of bacterial polysaccharides NMR experiments are important as is component analysis. A short description of immunochemical methods such as enzyme immunoassays is included. Two NMR techniques used for interaction studies, trNOE and STD NMR, are also discussed.

    The third part of the thesis discusses and summarizes the results from the included papers. The structures of the exopolysaccharides produced by two lactic acid bacteria are determined by one- and two dimensional NMR experiments. One is a heteropolysaccharide produced by Streptococcus thermophilus and the other a homopolysaccharide produced by Propionibacterium freudenreichii. The structure of an acidic polysaccharide from a marine bacterium with two serine residues in the repeating unit is also investigated. The structural and immunological relationship between two O-antigenic polysaccharides from Escherichia coli strain 180/C3 and O5 is discussed and investigated. Finally, interaction studies of an octasaccharide derived from the Salmonella enteritidis O-antigen and a bacteriophage are described which were performed with NMR experiments.

  • 126.
    Norinder, Jakob
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Asymmetric Synthesis and Mechanistic Studies on Copper(I)-Catalyzed Substitution of Allylic Substrates2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis deals with the copper-catalyzed substitution of allylic substrates.

    In the first part of this thesis, the synthesis of a series of metallocenethiolates is described. The thiolates were examined as ligands in the enantioselective copper(I)-catalyzed γ-substitution of allylic acetates.

    The second part describes a study on copper-catalyzed α-substitution of enantiomerically pure secondary allylic esters. It was observed that the degree of chirality transfer is strongly dependent on the reaction temperature. The loss of chiral information is consistent with an equilibration of the allylCu(III) intermediates prior to product formation, which is essential in order to realize a copper-catalyzed dynamic kinetic asymmetric transformation process.

    The third part describes a study on copper-catalyzed stereoselective α-substitution of enantiopure acyclic allylic esters. This method, when combined, with ruthenium and enzyme catalyzed dynamic kinetic resolution of allylic alcohols, provides a straightforward route to pharmaceutically important α-methyl carboxylic acids.

    The fourth part is a mechanistic study on the reaction of perfluoroallyl iodide with organocuprates. Experimental studies as well as theoretical calculations were used to explain the contrasting reactivity of perfluoroallyl iodide vs. allyl iodide in cuprate allylation reactions.

    In the fifth part, the development of a practical and useful method for the preparation of pentasubstituted acylferrocenes is presented.

  • 127.
    Närhi, Katja
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Studies on Palladium-Catalyzed Carbocyclizations of Allene-Substituted Olefins and 1,3-Dienes2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis describes the development and mechanistic studies of carbocyclization reactions of allene-substituted olefins and 1,3-dienes, catalyzed by palladium(0) and palladium(II). These reactions results in the formation of [n,3,0] bicyclic systems (n = 3-5) with high stereoselectivity and in good to excellent yields.

    The first carbocyclization presented is a novel palladium(0)-catalyzed cyclo- isomerization of allene-substituted olefins.

    Secondly an efficient aerobic biomimetic system has been developed for a Pd(II)-catalyzed allylic oxidative carbocyclization of allene-substituted olefins.

    Additionally, during the studies of palladium-catalyzed carbocyclizations of allene-substituted olefins, it was found that in the absence of palladium a mild thermal ene-reaction occurs. In this manner stereodefined, functionalized bicyclic compounds are obtained with good regioselectivity and in high yields.

    The third and fourth carbocyclization developed are a palladium(II)-catalyzed oxidation and a palladium(0)-catalyzed intramolecular telomerization of allene-substituted 1,3-dienes.

    A mechanistic study of the palladium(II)-catalyzed oxidation of allene-substituted 1,3-dienes was made, and reaction intermediates could be isolated. The stereochemistry of the reaction intermediates was assigned, and this made it possible to suggest a mechanism for the reaction. The presented mechanism is a trans carbopalladation of the 1,3-diene, where the allene act as the carbon nucleophile. Due to different stereochemical outcomes of the stoichiometric and catalytic reactions, this mechanism could only explain the stoichiometric reaction. Another mechanism for the catalytic reaction was suggested, which rationalizes both the regio- and stereochemistry of the products.

  • 128.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Fast, efficient and high-yielding routes to diaryliodonium salts2009In: European Symposium on Organic Chemistry (ESOC 16), Prague, Czech Republic, 2009, 2009Conference paper (Other academic)
  • 129.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Fast, efficient and high-yielding routes to diaryliodonium salts2009In: 44th EUCHEM Conference on Stereochemistry, Bürgenstock, Switzerland, May, 2009, 2009Conference paper (Other academic)
  • 130.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Fast, efficient and high-yielding routes to diaryliodonium salts2009In: XVIII EuCheMS Conference on Organometallic Chemistry, Gothenburg, Sweden, 2009, 2009Conference paper (Other academic)
  • 131.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Fast, efficient and high-yielding routes to diaryliodonium salts2009In: EUCHEMS Young Investigator Workshop, Liblice, Czech Republic, 2009, 2009Conference paper (Other academic)
  • 132.
    Olofsson, Berit
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Aggarwal, Varinder K.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Enantioselective alfa-Arylation of Ketones: Application to the Synthesis of (–)-Epibatidine2006In: Sterochemistry, Bürgenstock, Switzerland, 2006Conference paper (Other (popular science, discussion, etc.))
  • 133.
    Olofsson, Berit
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Aggarwal, Varinder K.
    Bristol University, UK.
    Enantioselective alfa-Arylation of Ketones: Application to the Synthesis of (–)-Epibatidine2006In: Organikerdagarna, Kalmar, Sweden, 2006, p. Le21, P47-Conference paper (Other (popular science, discussion, etc.))
    Abstract [en]

    The enantioselective introduction of electrophiles alfa to carbonyl compounds occupies a central position in asymmetric synthesis. Although asymmetric alkylations have been well developed, high enantioselectivity in α-arylation of ketones has only been achieved in a limited number of cases.

    We have developed a direct arylation reaction of cyclohexanones, employing diaryl iodonium(III) salts as electrophiles. The reaction was made enantioselective by the use of a chiral base, resulting in 2,4-substituted cyclohexanones in high yields and with high enantiomeric excesses and diastereoselectivities.

    This methodology was applied in a short, enantioselective synthesis of (–)-Epibatidine, an alkaloid recently isolated from the Ecuadorian poison frog Epipedobates tricolor. The synthesis was accomplished in 6 steps and 31% overall yield, thus providing the shortest and most efficient asymmetric route to this important compound to date.

  • 134.
    Olofsson, Berit
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Aggarwal, Varinder K.
    Bristol University, UK.
    Synthesis of Novel Heteroaryl Iodonium Salts and Enantioselective a-Arylation of Cyclohexanones2006In: 2nd Int. Conference on Hypervalent Iodine, 2006Conference paper (Other academic)
    Abstract [en]

    We have developed a direct arylation reaction of cyclohexanones employing diaryl iodonium(Ill) salts as electrophiles. The

    reaction was made enantiosilective by the use of a chiral base, resultinginZ,4-disubstituted cyclohexanones in high yields and with high enantiomeric excesses and diastereoselectivities. Novel heteroaryl iodonium salts were subsequently synthesized and employed in the coupling to variously substituted cyclohexanones.

  • 135.
    Olsson, Ulrika
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Structural Studies of O-antigen polysaccharides, Synthesis of 13C-labelled Oligosaccharides and Conformational Analysis thereof, using NMR Spectroscopy2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    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 E. coli bacteria were determined using NMR spectroscopy. The O-antigenic PS from E. coli 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 E. coli O176 (paper II) is built up of a linear tetrasaccharide consisting of two different monosaccharides.

    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.

  • 136.
    Olsson, Vilhelm
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Development of New Synthetic Routes to Organoboronates by Catalytic Allylic Substitution and C-H bond Functionalization2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis describes the development of new catalytic methods for the synthesis and application of organometallic reagents, mainly focusing on allylboronic acid derivatives. Thus, palladium pincer-complex catalysis has been applied for extending the scope of palladiumcatalyzed borylation reactions in the synthesis of regio- and stereodefined functionalized allylboronic acid derivatives. These novel allylboronic acids were also employed as substrates in palladium catalyzed regioselective coupling reactions with iodobenzenes. We have also developed a new one-pot sequence based on preparation of allyl- and vinylboronates

    via catalytic carbon-hydrogen bond activation/borylation reactions. The synthetic scope of the reaction as well as mechanistic studies on the borylation process are presented. Finally, the synthesis of new chiral palladium pincer-complexes is described. These species were employed as catalysts in asymmetric electrophilic allyation of imines.

  • 137.
    Pascanu, Vlad
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bermejo Gomez, Antonio
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ayats, Carles
    Platero-Prats, Ana Eva
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Carson, Fabian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Su, Jie
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Yao, Qingxia
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Pericas, Miquel A.
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Martin-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Double-Supported Silica-Metal-Organic Framework Palladium Nanocatalyst for the Aerobic Oxidation of Alcohols under Batch and Continuous Flow Regimes2015In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 5, no 2, p. 472-479Article in journal (Refereed)
    Abstract [en]

    Stable and easily synthesized metal-organic framework MIL-88B-NH2 represents an attractive support for catalysts employed in oxidation reactions, which are typically performed under relatively harsh conditions. However, MIL-88B-NH2, the thermodynamic polymorph of the more popular MIL-101-NH2, has been rarely employed in catalytic applications because of a difficult impregnation process caused by the flexible nature of the framework. We report herein a new catalyst denoted Pd@MIL-88B-NH2 (8 wt % Pd), the first example of metallic nanoparticles successfully impregnated in the pores of MIL-88B-NH2. Furthermore, by enclosing the MOF crystals in a tailored protective coating of SiO2 nanoparticles, an even more enduring material was developed and applied to the aerobic oxidation of benzylic alcohols. This doubly supported catalyst Pd@MIL-88B-NH2@nano-SiO2 displayed high activity and excellent performance in terms of endurance and leaching control. Under batch conditions, a very convenient and efficient recycling protocol is illustrated, using a teabag approach. Under continuous flow, the catalyst was capable of withstanding 7 days of continuous operation at 110 degrees C without deactivation. During this time, no leaching of metallic species was observed, and the material maintained its structural integrity.

  • 138.
    Pascanu, Vlad
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Carson, Fabian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Vico Solano, Marta
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Su, Jie
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Johansson, Magnus J.
    Martín-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Selective Heterogeneous C−H Activation/Halogenation Reactions Catalyzed by Pd@MOF Nanocomposites2016In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 22, no 11, p. 3729-3737Article in journal (Refereed)
    Abstract [en]

    A directed heterogeneous C−H activation/halogenation reaction catalyzed by readily synthesized Pd@MOF nanocatalysts was developed. The heterogeneous Pd catalysts used were a novel and environmentally benign Fe-based metal–organic framework (MOF) (Pd@MIL-88B-NH2(Fe)) and the previously developed Pd@MIL-101-NH2(Cr). Very high conversions and selectivities were achieved under very mild reaction conditions and in short reaction times. A wide variety of directing groups, halogen sources, and substitution patterns were well tolerated, and valuable polyhalogenated compounds were synthesized in a controlled manner. The synthesis of the Pd-functionalized Fe-based MOF and the recyclability of the two catalysts are also presented.

  • 139.
    Pascanu, Vlad
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hansen, Peter R.
    Bermejo Gomez, Antonio
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ayats, Carles
    Platero-Prats, Ana E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Johansson, Magnus J.
    Pericas, Miquel A.
    Martín-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Highly Functionalized Biaryls via Suzuki-Miyaura Cross-Coupling Catalyzed by Pd@MOF under Batch and Continuous Flow Regimes2015In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 8, no 1, p. 123-130Article in journal (Refereed)
    Abstract [en]

    A diverse set of more than 40 highly functionalized biaryls was synthesized successfully through the Suzuki-Miyaura cross-coupling reaction catalyzed by Pd nanoparticles supported in a functionalized mesoporous MOF (8 wt% Pd@MIL-101(Cr)-NH2). This could be achieved under some of the mildest conditions reported to date and a strong control over the leaching of metallic species could be maintained, despite the presence of diverse functional groups and/or several heteroatoms. Some of the targeted molecules are important intermediates in the synthesis of pharmaceuticals and we clearly exemplify the versatility of this catalytic system, which affords better yields than currently existing commercial procedures. Most importantly, Pd@MIL-101-NH2 was packed in a micro-flow reactor, which represents the first report of metallic nanoparticles supported on MOFs employed in flow chemistry for catalytic applications. A small library of 11 isolated compounds was created in a continuous experiment without replacing the catalyst, demonstrating the potential of the catalyst for large-scale applications.

  • 140.
    Pascanu, Vlad
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Yao, Qingxia
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bermejo Gomez, Antonio
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Gustafsson, Mikaela
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Yun, Yifeng
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Wan, Wei
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Samain, Louise
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Martin-Matute, Belen
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sustainable Catalysis: Rational Pd Loading on MIL-101Cr-NH2 for More Efficient and Recyclable Suzuki-Miyaura Reactions2013In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 19, no 51, p. 17483-17493Article in journal (Refereed)
    Abstract [en]

    Palladium nanoparticles have been immobilized into an amino-functionalized metal-organic framework (MOF), MIL-101Cr-NH2, to form Pd@MIL-101Cr-NH2. Four materials with different loadings of palladium have been prepared (denoted as 4-, 8-, 12-, and 16wt%Pd@MIL-101Cr-NH2). The effects of catalyst loading and the size and distribution of the Pd nanoparticles on the catalytic performance have been studied. The catalysts were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, powder X-ray diffraction (PXRD), N-2-sorption isotherms, elemental analysis, and thermogravimetric analysis (TGA). To better characterize the palladium nanoparticles and their distribution in MIL-101Cr-NH2, electron tomography was employed to reconstruct the 3D volume of 8wt%Pd@MIL-101Cr-NH2 particles. The pair distribution functions (PDFs) of the samples were extracted from total scattering experiments using high-energy X-rays (60keV). The catalytic activity of the four MOF materials with different loadings of palladium nanoparticles was studied in the Suzuki-Miyaura cross-coupling reaction. The best catalytic performance was obtained with the MOF that contained 8wt% palladium nanoparticles. The metallic palladium nanoparticles were homogeneously distributed, with an average size of 2.6nm. Excellent yields were obtained for a wide scope of substrates under remarkably mild conditions (water, aerobic conditions, room temperature, catalyst loading as low as 0.15mol%). The material can be recycled at least 10times without alteration of its catalytic properties.

  • 141.
    Pathipati, Stalin R.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Selander, Nicklas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Stereoselective synthesis of bicyclo[3.n.1]alkenone frameworks by Lewis acid-catalysis2017In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 53, no 82, p. 11353-11356Article in journal (Refereed)
    Abstract [en]

    An intermolecular cyclization of alkynyl enones with cyclic ketones for the synthesis of bicyclo[3.n.1]alkenones is reported. This protocol exhibits a high functional group tolerance and provides access to a variety of bicyclic systems found as skeletons in many natural products.

  • 142.
    Pathipati, Stalin R.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Singh, Vipender
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Selander, Nicklas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lewis Acid Catalyzed Annulation of Nitrones with Oxiranes, Aziridines, and Thiiranes2015In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 17, no 18, p. 4506-4509Article in journal (Refereed)
    Abstract [en]

    A highly selective Lewis acid catalyzed annulation of three-membered heterocycles with nitrones has been developed. Oxiranes, aziridines, and thiiranes were used as substrates for the synthesis of various six-membered heterocycles using Al or In catalysts. This catalytic protocol demonstrates a broad substrate scope and provides access to new structural motifs in high yields and in excellent selectivity under mild reaction conditions.

  • 143.
    Pathipati, Stalin R.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    van der Werf, Angela
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Selander, Nicklas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Diastereoselective Synthesis of Cyclopenta[c]furans by a Catalytic Multicomponent Reaction2016In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 55, no 39, p. 11863-11866Article in journal (Refereed)
    Abstract [en]

    A diastereoselective three-component reaction between alkynyl enones, aldehydes and secondary amines is reported. With the aid of a benign indium catalyst, a range of highly substituted cyclopenta[c]furan derivatives can be obtained in a single-step procedure. The formation of the stereodefined heterocyclic motifs takes place via in situ generation of enamines followed by two sequential cyclization steps.

  • 144.
    Pendrill, Robert
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Conformations of Flexible Oligosaccharides: Molecular Simulations and NMR spectroscopy2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The conformational preferences of several oligosaccharides are investigated herein using a combination of NMR spectroscopy and molecular dynamics (MD) simulations, focusing on the torsion angles associated with the glycosidic linkages.

    Strategies for obtaining usable J-HMBC spectra for carbons with an adjacent 13C label are described. By employing a selective pulse or a constant time modification, spectra free from interferences are obtained for site-specifically 13C labeled oligosaccharides.

    Intermolecular hydrogen bonding in sucrose is investigated using MD simulations performed at different concentrations. One of the most frequent intermolecular hydrogen bonds in the simulations, O3f∙∙∙HO3g, was detected using the HSQC-TOCSY NMR experiment.

    Based on MD simulations and NMR spectroscopy, the conformational ensemble for a trisaccharide segment of the LeaLex hexasaccharide is proposed to feature conformational exchange between conformations with positive and negative values for the ψ3 torsion angle in the β-D-GlcpNAc-(1→3)-β-D-Galp linkage.

    Using MD simulations, the conformation of the N-acetyl group is shown to influence the glycosidic conformation at a nearby linkage in two oligosaccharides.

    Short (1→6)-linked oligosaccharides are shown to exhibit conformational exchange at the ω and ψ torsion angles. Notably, the former torsion angle populates states with ψ ≈ ±90°. Conformationally sensitive homo- and heteronuclear coupling constants are determined using various NMR experiments. The experimental data, including effective distances from NOESY obtained for two of the compounds, is used to improve the representation of the ω torsion angle in the CHARMM36 force field.

  • 145.
    Pendrill, Robert
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Methyl 4-O-benzyl-alpha-l-rhamno-pyrano-side2014In: Acta Crystallographica Section E: Structure Reports Online, ISSN 1600-5368, E-ISSN 1600-5368, Vol. 70, p. o561-o562Article in journal (Refereed)
  • 146.
    Pendrill, Robert
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Säwén, Elin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Conformation and Dynamics at a Flexible Glycosidic Linkage Revealed by NMR Spectroscopy and Molecular Dynamics Simulations: Analysis of β-ʟ-Fucp-(1→6)-α-ᴅ-Glcp-OMe in Water Solution2013In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 117, no 47, p. 14709-14722Article in journal (Refereed)
    Abstract [en]

    The intrinsic flexibility of carbohydrates facilitates different 3D structures in response to altered environments. At glycosidic (1 -> 46)-linkages, three torsion angles are variable, and herein the conformation and dynamics of beta-1.-Fucp-(1 -> 6)-alpha-D-Glcp-OMe are investigated using a combination of NMR spectroscopy and molecular dynamics (MD) simulations. The disaccharide shows evidence of conformational averaging for the psi and co torsion angles, best explained by a four-state conformational distribution. Notably, there is a significant population of conformations having psi = 85 degrees (clinal) in addition to those having psi = 180 degrees (anfiperiplanar). Moderate differences in C-13 R-1 relaxation rates are found to be best explained by axially symmetric tumbling in combination with minor differences in librational motion for the two residues, whereas the isomerization motions are occurring too slowly to significantly to the observed relaxation rates. The MD simulation was found to give a reasonably good agreement with experiment, especially with respect to diffusive properties, among which the rotational anisotropy, D parallel to/D parallel to, is found to be 2.35. The force field employed showed too narrow omega torsion angles in the gauche trans and gauche gauche states as well as overestimating the population of the gauche trans conformer. This information can subsequently be used in directing parameter developments and emphasizes the need for refinement of force fields for (1 -> 6)-linked carbohydrates.

  • 147.
    Pendrill, Robert
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sørensen, Ole W.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Suppressing one-bond homonuclear 13C,13C scalar couplings in the J-HMBC NMR experiment: application to 13C site-specifically labeled oligosaccharides2014In: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 52, no 3, p. 82-86Article in journal (Refereed)
    Abstract [en]

    Site-specific C-13 isotope labeling is a useful approach that allows for the measurement of homonuclear C-13,C-13 coupling constants. For three site-specifically labeled oligosaccharides, it is demonstrated that using the J-HMBC experiment for measuring heteronuclear long-range coupling constants is problematical for the carbons adjacent to the spin label. By incorporating either a selective inversion pulse or a constant-time element in the pulse sequence, the interference from one-bond C-13,C-13 scalar couplings is suppressed, allowing the coupling constants of interest to be measured without complications. Experimental spectra are compared with spectra of a nonlabeled compound as well as with simulated spectra. The work extends the use of the J-HMBC experiments to site-specifically labeled molecules, thereby increasing the number of coupling constants that can be obtained from a single preparation of a molecule.

  • 148.
    Persson, Andreas K. Å.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium(II)-Catalyzed Oxidative Cyclization Strategies: Selective Formation of New C-C and C-N Bonds2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The main focus of this thesis has been directed towards preparation and oxidative carbocyclization of en-, dien- and aza-enallenes.

    In the first part of this thesis, a stereoselective oxidative carbocyclization of dienallenes was realized. By employing cheap and readily available palladium trifluoroacetate we were able to efficiently cyclize a variety of dienallenes into hydroxylated carbocycles in high yield and high selectivity. This oxidative process was compatible with two different reoxidation protocols: one relying on p-benzoquinone (BQ) as the oxidant and the other employing molecular oxygen as the oxidant.

    In the second part of the thesis the carbocyclization methodology was extended to include carbocyclization of aza-enallenes. This was achieved in two distinct steps. First, a copper-catalyzed coupling of allylic sulfonamides with bromoallenes was developed, giving access to the corresponding aza-enallenes. Subjecting these substrates to catalytic amounts of palladium acetate, along with BQ as the oxidant, rendered N-heterocycles in good yield. The reactivity of these N-heterocycles towards activated dienophiles was later exploited in a tandem (aerobic) oxidative carbocyclization/Diels-Alder reaction.

    The third topic involves efficient oxidative arylative/borylative carbocyclization of enallenes. These reactions, catalyzed by palladium acetate, relies on transmetallation of a (σ-alkyl)palladium(II) intermediate with diboranes or arylboronic acids. With this novel methodology we were able to obtain an array of arylated or borylated carbocycles, as single diastereomers, in high yield.

    Finally, we developed a palladium(II)-catalyzed cyclization of allylic carbamates. This mild, operationally simple, and scalable catalytic reaction opens up access to an array of oxazolidinones in high yield and excellent diastereoselectivity.

  • 149.
    Peters, Byron
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Iridium Catalysed Asymmetric Hydrogenation of Olefins and Isomerisation of Allylic Alcohols2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The work described in this thesis is focused on exploring the efficacy of asymmetric iridium catalysis in the hydrogenation of challenging substrates, including precursors to chiral sulfones and chiral cyclohexanes. Furthermore, iridium catalysis was used to isomerise allylic alcohols to aldehydes, and in a formal total synthesis of Aliskiren (a renin inhibitor). A large variety of unsaturated sulfones (cyclic, acyclic, vinylic, allylic and homoallylic) were prepared and screened in the iridium catalysed hydrogenation reaction using a series of previously developed N,P-ligated Ir-catalysts. The outcome was a highly enantioselective (>90% ee) protocol to prepare sulfones bearing chiral carbon scaffolds, sometimes having purely aliphatic substituents at the stereogenic centre. Furthermore, performing the Ramberg-Bäcklund reaction on the chiral products, under optimised conditions, produced cyclic and acyclic unsaturated derivatives without erosion of enantiomeric excess. This hydrogenation protocol was also successful in the hydrogenation of a number of cyclohexene-containing compounds. Minimally functionalised, functionalised and heterocycle-containing cyclohexenes were hydrogenated in up to 99% ee. Hitherto, both chiral sulfones and chiral cyclohexanes have been challenging targets for most catalytic asymmetric methodologies. Although the preparation of aldehydes and ketones by isomerisation of the corresponding allylic alcohol is well established, there has been limited success in the development of good enantioselective protocols. For the isomerisation of a number γ,γ-allylic alcohols to the corresponding chiral aldehydes, high enantioselectivities (up to >99% ee) and modest yields were achieved using an N,P-iridium catalyst. Noteworthy is the high selectivity obtained for isomerisation of and dialkyl γ,γ-allylic alcohols, which prior to this study had been difficult to isomerise in high enantioselectivity. Preparation of a key intermediate used in the synthesis of Aliskiren, a renin inhibitor drug was also accomplished. Using a convergent synthesis strategy, two allylic alcohol fragments were hydrogenated with high enantiomeric excess (>92% ee). These fragments were then joined using a Julia-Kocienski reaction, providing >95% geometry around the C=C bond, which was crucial for the subsequent steps in the synthesis.

  • 150.
    Platero-Prats, Ana E.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Argonne National Laboratory, USA.
    Bermejo Gómez, Antonio
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Chapman, Karena W.
    Martin-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Functionalising metal-organic frameworks with metal complexes: the role of structural dynamics2015In: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, Vol. 17, no 40, p. 7632-7635Article in journal (Refereed)
    Abstract [en]

    A series of iridium-functionalised UiO-67 metal-organic frameworks (MOFs) were synthesised under conditions that simulate kinetically- and thermodynamically-controlled regimes. The degree of functionalisation depends on the reaction time and relative acidity of the native- and metallo-linkers, and can be optimised by controlling the reaction time.

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