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  • 201.
    Qiu, Youai
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Posevins, Daniels
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Selective Palladium-Catalyzed Allenic C-H Bond Oxidation for the Synthesis of [3]Dendralenes2017In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 56, no 42, p. 13112-13116Article in journal (Refereed)
    Abstract [en]

    A highly selective palladium-catalyzed allenic C-H bond oxidation was developed, and it provides a novel and straightforward synthesis of [3]dendralene derivatives. A variety of [3]dendralenes with diverse substitution patterns are accessible with good efficiency and high stereoselectivity. The reaction tolerates a broad substrate scope containing various functional groups on the allene moiety, including ketone, aldehyde, ester, and phenyl groups. Also, a wide range of olefins with both electron-donating and electron-withdrawing aryls, acrylate, sulfone, and phosphonate groups are tolerated.

  • 202.
    Qiu, Youai
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Yang, Bin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Jiang, Tuo
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhu, Can
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium-Catalyzed Oxidative Cascade Carbonylative Spirolactonization of Enallenols2017In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 56, no 12, p. 3221-3225Article in journal (Refereed)
    Abstract [en]

    A highly selective palladium-catalyzed oxidative carbonylation/carbocyclization/alkoxycarbonylation of enallenols to afford spirolactones bearing an all-carbon quaternary center was developed. This transformation involves the overall formation of three C-C bonds and one C-O bond through a cascade insertion of carbon monoxide (CO), an olefin, and CO. Preliminary experiments on chiral anion-induced enantioselective carbonylation/carbocyclization of enallenols afforded spirolactones with moderate enantioselectivity.

  • 203.
    Qiu, Youai
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Yang, Bin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhu, Can
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Highly selective olefin-assisted palladium-catalyzed oxidative carbocyclization via remote olefin insertion2017In: Chemical Science, ISSN 2041-6520, E-ISSN 2041-6539, Vol. 8, no 1, p. 616-620Article in journal (Refereed)
    Abstract [en]

    A highly selective olefin-assisted palladium-catalyzed oxidative carbocyclization via remote olefin insertion to afford cyclohexenes has been developed. It was shown that the assisting olefin moiety was indispensable for the formation of the cyclohexene product. Furthermore, preliminary studies on chiral anion-induced asymmetrical carbocyclization-borylation of enallenes have been carried out.

  • 204.
    Quan, Xu
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hydrogenation, Transfer Hydrogenation and Hydrogen Transfer Reactions Catalyzed by Iridium Complexes2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The work described in this thesis is focused on the development of new bidentate iridium complexes and their applications in the asymmetric reduction of olefins, ketones and imines. Three new types of iridium complexes were synthesized, which included pyridine derived chiral N,P-iridium complexes, achiral NHC complexes and chiral NHC-phosphine complexes. A study of their catalytic applications demonstrated a high efficiency of the N,P-iridium complexes for asymmetric hydrogenation of olefins, with good enantioselectivity. The carbene complexes were found to be very efficient hydrogen transfer mediators capable of abstracting hydrogen from alcohols and subsequently transfer it to other unsaturated bonds. This hydrogen transferring property of the carbene complexes was used in the development of C–C and C–N bond formation reactions via the hydrogen borrowing process. The complexes displayed high catalytic reactivity using 0.5–1.0 mol% of the catalyst and mild reaction conditions. Finally chiral carbene complexes were found to be activated by hydrogen gas. Their corresponding iridium hydride species were able to reduce ketones and imines with high efficiency and enantioselectivity without any additives, base or acid.

  • 205.
    Quan, Xu
    et al.
    Uppsala University, Sweden.
    Parihar, Vijay Singh
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bera, Milan
    University of KwaZulu-Natal, South Africa.
    Andersson, Pher G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry. University of KwaZulu-Natal, South Africa.
    Iridium Catalysts with Chiral Bicyclic Pyridine-Phosphane Ligands for the Asymmetric Hydrogenation of Olefins2014In: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, Vol. 2014, no 1, p. 140-146Article in journal (Refereed)
    Abstract [en]

    New bicyclic pyridine-phosphane ligands were prepared, and their iridium complexes were evaluated in asymmetric hydrogenation of trisubstituted olefins with non-coordinating and weakly coordinating substituents. The iridium catalysts showed high reactivity and enantioselectivity for both types of olefins.

  • 206.
    Rabten, Wangchuk
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    The Use of N,P-Iridium and N,P-Palladium Complexes in Asymmetric Synthesis2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The work presented in this thesis concerns asymmetric catalysis using chiral N,P-ligands and iridium or palladium transition metals. The first part  (Chapters 2 and 3) highlights the N,P-iridium catalyzed asymmetric hydrogenation of 1,4-cyclohexadienes having functionalized or unfunctionalized substituents, including allylsilane side chains. A series of N,P-iridium catalysts were synthesized and screened on a number of cyclohexadienes. The developed N,P-iridium catalysts have provided excellent chemo-, regio- and enantioselectivity for most of the products obtained. For substrates having an allylsilane sidechain, the chiral cyclic allylsilane products were used to induce stereocontrol in a subsequent Hosomi-Sakurai reaction using TiCl4 as Lewis acid and aldehydes as electrophiles. The corresponding homoallylic alcohols were obtained in good to excellent diastereoselectivity. 

    The second part (Chapter 4) describes the N,P-iridium catalyzed asymmetric hydrogenation of various vinyl fluorides. A number of tri- and tetrasubstituted vinyl fluorides were synthesized and evaluated for the asymmetric hydrogenation. The corresponding saturated chiral fluoro compounds were obtained in very high enantioselectivity (up to 99% ee). The defluorination, usually known to occur under the catalytic hydrogenation conditions, were not observed for the majority of the substrates. 

    Finally, Chapter 5 describes the application of N,P-ligands in the asymmetric cycloisomerization of 1,6-enynes using a palladium precatalyst. The enantioselectivities for the products were found to depend both on the substrate as well as the hydrogen source. These developed catalytic reactions provide attractive methods to create multiple stereogenic centers in a molecule in relatively few steps from readily available starting materials.

  • 207.
    Rabten, Wangchuk
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Margarita, Cristiana
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Andersson, Pher G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ir-Catalyzed Asymmetric and Regioselective Hydrogenation of Cyclic Allylsilanes and Generation of Quaternary Stereocenters via the Hosomi-Sakurai Allylation2018In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 24, no 7, p. 1681-1685Article in journal (Refereed)
    Abstract [en]

    A number of cyclic dienes containing the allylsilane moiety were prepared via Birch reduction and subjected to iridium-catalyzed regioselective and asymmetric hydrogenation, which provided chiral allylsilanes in high conversion and enantiomeric excess (up to 99 % ee). The compounds were successively used in the Hosomi-Sakurai allylation with various aldehydes employing TiCl4 as Lewis acid, providing adducts with two additional stereogenic centers in excellent diastereoselectivity.

  • 208.
    Ramstadius, Clinton
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of Carbohydrate Mimics and Development of a Carbohydrate Epimerisation Method2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis the synthesis of several hydrolytically stable carbohydrate mimics with the potential to function as glycosidase or lectin inhibitors are described. This work is presented in Chapters 2-5.

    Chapters 2 and 3 describe synthetic efforts for producing carbasugars, and include the first synthesis of 1,2-bis-epi-valienamine and the preparation of two previously known aminocarbasugars. All three compounds were synthesised starting from D-mannose, using ring-closing metathesis as the key step. 1,2-Bis-epi-valienamine was found to inhibit Cellulomonas fimi β-mannosidase with a Ki value of 140 mM. Also included is the development of a novel synthetic route from cheap D-fructose to three mannose-mimicking carbasugars using a ring-closing metathesis strategy. Two of the compounds are potential inhibitors of the FimH adhesin.

    In Chapters 4 and 5 the synthesis of a number of pseudodisaccharides are presented; valienamine- and epi-valienamine-containing pseudodisaccharides and a small library of S-linked pseudodisaccharides were prepared. Various synthetic strategies were explored, including an alkylation strategy, Mitsunobu couplings, and sulfonate displacements. This is the first report on the synthesis of a valienamine pseudodisaccharide with β-lyxo-configuration. Two of the S-linked pseudodisaccharides were found to bind to Concanavalin A with high affinity.

    The final chapter (Chapter 6) of this thesis focuses on the development of a carbohydrate epimerisation method using transition metal catalysis. Two equilibrium constants involving gluco/manno- and gluco/allo-alcohols were determined via this method.

  • 209.
    Reitti, Marcus
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Diaryliodonium Salts: Synthesis, Applications and Computational Investigations2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Organic chemists have the ability to create complex organic molecules by connecting molecular building blocks in different ways. To name a few, these molecules are used as medicines, pesticides or in our household electronics, and are therefore crucial to life as we know it. While many excellent methods for the connection of these fragments are known, serious issues regarding efficiency and sustainability remain. Our research concerns the use of diaryliodonium salts as a way of improving on these issues. Diaryliodonium salts are hypervalent iodine reagents used to transfer aryl groups to suitable nucleophiles. This thesis concerns the synthesis of these reagents and their use in the formation of carbon-nitrogen and carbon-oxygen bonds.

    The first project investigates the possibility to synthesize unsymmetrical diaryliodonium salts starting from elemental iodine and arenes, as such a method could be more cost efficient and sustainable compared to existing methods starting from iodoarenes. It was found that highly sterically congested diaryliodonium salts could be synthesized in high yields.

    Next, we applied diaryliodonium salts in the arylation of nitrite to form aromatic nitro compounds. The methodology offered a broad scope with good to excellent yields. Furthermore, we presented the in situ functionalization of diaryliodonium salts that had been formed from iodoarenes and arenes. This conceptually novel approach could be a step towards a catalytic reaction using diaryliodonium salts.

    In the third project we investigated the mechanisms of O-arylations with diaryliodonium salts to provide a deeper understanding of the reaction pathways involved in product and byproduct formation. Reactions between electron-rich diaryliodonium salts, hydroxides or secondary alcohols were studied.  When using hydroxide as the nucleophile, the side products could be suppressed by the addition of aryne traps, suggesting such an intermediate in the reaction. A novel mechanism for the formation of the aryne was proposed based on DFT calculations.  When alcohols were used we detected the oxidation of the alcohol rather than aryne products. The oxidized product was shown to not originate from arynes or a radical process but was formed via an intramolecular deprotonation from a 4-coordinated intermediate as suggested by DFT-calculations and experiments.

    In the final project we developed two complementary methods for the synthesis of phenols using hydroxide surrogates as nucleophiles. These compounds have previously been difficult to make using diaryliodonium salts due to aryne formation or overarylation to form diaryl ethers. The first method used hydrogen peroxide as the surrogate and allowed formation of electron-deficient and moderately electron-rich phenols. The synthesis of ortho-alkyl substituted phenols could be accomplished by using silanols as the surrogate. This allowed us to synthesize several highly congested phenols in good yields. Highly electron-rich diaryliodonium salts were, however, not compatible with either of the two methods.

  • 210.
    Reitti, Marcus
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Villo, Piret
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    One-Pot C-H Functionalization of Arenes by Diaryliodonium Salts2016In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 55, no 31, p. 8928-8932Article in journal (Refereed)
    Abstract [en]

    A transition-metal-free, mild, and highly regioselective synthesis of nitroarenes from arenes has been developed. The products are obtained in a sequential one-pot reaction by nitration of iodine(III) reagents with two carbon ligands, which are formed in situ from iodine(I). This novel concept has been extended to formation of aryl azides, and constitutes an important step towards catalytic reactions with these hypervalent iodine reagents. An efficient nitration of isolated diaryl-iodonium salts has also been developed, and the mechanism is proposed to proceed by a [2,2] ligand coupling pathway.

  • 211. Rojas-Macias, Miguel A.
    et al.
    Ståhle, Jonas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Luetteke, Thomas
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Development of the ECODAB into a relational database for Escherichia coli O-antigens and other bacterial polysaccharides2015In: Glycobiology, ISSN 0959-6658, E-ISSN 1460-2423, Vol. 25, no 3, p. 341-347Article in journal (Refereed)
    Abstract [en]

    Escherichia coli O-antigen database (ECODAB) is aweb-based application to support the collection of E. coli O-antigen structures, polymerase and flippase amino acid sequences, NMR chemical shift data of O-antigens as well as information on glycosyltransferases (GTs) involved in the assembly of O-antigen polysaccharides. The database content has been compiled from scientific literature. Furthermore, the system has evolved from being a repository to one that can be used for generating novel data on its own. GT specificity is suggested through sequence comparison with GTs whose function is known. The migration of ECODAB to a relational database has allowed the automation of all processes to update, retrieve and present information, thereby, endowing the system with greater flexibility and improved overall performance. ECODAB is freely available at http://www.casper.organ.su.se/ECODAB/. Currently, data on 169 E. coli unique O-antigen entries and 338 GTs is covered. Moreover, the scope of the database has been extended so that polysaccharide structure and related information from other bacteria subsequently can be added, for example, from Streptococcus pneumoniae.

  • 212.
    Rönnols, Jerk
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Structure, dynamics and reactivity of carbohydrates: NMR spectroscopic studies2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The main focus of this thesis is on the ring conformations of carbohydrate molecules; how the conformational equilibria and the rates of the associated interconversions are affected by the molecular constitution and their surroundings.

    The conformational equilibria of a group of amine linked pseudodisaccharides, designed as potential glycosidase inhibitors, comprising α-D-altrosides are described in Chapter 3. The OS2 conformation was largely populated, and the ring conformation was found to depend on the charge of the amine functionality.

    The conformations of β-D-xylopyranoside derivatives with naphthyl-based aglycones, which are potential anti-cancer agents, are described in chapter 4. Solvent dependent flexibility was observed. Intramolecular hydrogen bonds were concluded to be involved in the stabilization of 1C4 conformers in non-hydrogen bonding solvents of low polarity.

    Chapter 5 describes the first measurements of the conformational exchange rates of mannuronic acid ester derivatives between the 4C1 and 1C4 conformations, through DNMR measurements. The relative reactivity of glycosyl triflates as electrophiles in glycosylation reactions were investigated with NMR-based competition experiments.

    In Chapter 6, investigations of ruthenium-catalyzed epimerizations of the allylic alcohols of glycal derivatives, and stereoselective synthesis of esters through a DYKAT protocol, are described. The kinetics of the epimerizations were elaborated through different NMR-spectroscopic methods.

    Chapter 7 describes additions of NMR chemical shift data of mono- and oligosaccharides to database of the computer program CASPER, and applications thereof.

  • 213.
    Rönnols, Jerk
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Manner, Sophie
    Ellervik, Ulf
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Conformational effects due to stereochemistry and C3-substituents in xylopyranoside derivatives as studied by NMR spectroscopy2014In: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 12, no 40, p. 8031-8035Article in journal (Refereed)
    Abstract [en]

    Glycosaminoglycans contain a beta-D-xylopyranose residue at its reducing end, which links the polysaccharide to the protein in proteoglycans. 2-Naphthyl beta-D-xylopyranosides have shown inhibition of tumor growth and we herein investigate conformation and dynamics of compounds structurally and stereochemically modified at the C3 position as well as the influence of solvent. The 3-deoxygenated compound, the 3-C-methyl-substituted beta-D-xylopyranoside, beta-D-ribopyranoside, the 3-C-methyl-substituted beta-D-ribopyranoside as well as 2-naphthyl beta-D-xylopyranoside were analyzed by NMR spectroscopy. Conformational equilibria were dependent on the solvent of choice, either methanol-d(4) or chloroform-d, with mainly C-4(1) and C-1(4) conformations present but also skew conformations to some extent. Intramolecular hydrogen bonding was concluded to be important for the 3-C-methyl-substituted beta-D-xylopyranosides in the non-polar solvent. Dynamic NMR (DNMR) spectroscopy was carried out for the 3-deoxygenated compound, which at 25 degrees C in methanol-d(4) exists with equally populated states of the C-4(1) and the C-1(4) conformations, but at -100 degrees C only a few percent is present of the latter. Using C-13 NMR detection for DNMR, resonance lines were shown to broaden at -40 degrees C and to sharpen again below -90 degrees C, without the emergence of a second set of NMR resonances, a typical behavior for an unequally populated equilibrium. The enthalpy and entropy activation barriers were calculated and resulted in Delta H-double dagger = 47.3 kJ mol(-1) and Delta S-double dagger = 54 J mol(-1) K-1.

  • 214.
    Rönnols, Jerk
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Pendrill, Robert
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Fontana, Carolina
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hamark, Christoffer
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Angles d'Ortoli, Thibault
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Engström, Olof
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ståhle, Jonas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zaccheus, Mona V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Säwén, Elin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hahn, Liljan E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Iqbal, Shahzad
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Complete H-1 and C-13 NMR chemical shift assignments of mono- to tetrasaccharides as basis for NMR chemical shift predictions of oligosaccharides using the computer program CASPER2013In: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 380, p. 156-166Article in journal (Refereed)
    Abstract [en]

    H-1 and C-13 NMR chemical shift data are used by the computer program CASPER to predict chemical shifts of oligo- and polysaccharides. Three types of data are used, namely, those from monosaccharides, disaccharides, and trisaccharides. To improve the accuracy of these predictions we have assigned the H-1 and C-13 NMR chemical shifts of eleven monosaccharides, eleven disaccharides, twenty trisaccharides, and one tetrasaccharide; in total 43 compounds. Five of the oligosaccharides gave two distinct sets of NMR resonances due to the alpha- and beta-anomeric forms resulting in 48 H-1 and C-13 NMR chemical shift data sets. In addition, the pyranose ring forms of Neu5Ac were assigned at two temperatures, due to chemical shift displacements as a function of temperature. The H-1 NMR chemical shifts were refined using total line-shape analysis with the PERCH NMR software. H-1 and C-13 NMR chemical shift predictions were subsequently carried out by the CASPER program (http://www.casper.organ.su.se/casper/) for three branched oligosaccharides having different functional groups at their reducing ends, namely, a mannose-containing pentasaccharide, and two fucose-containing heptasaccharides having N-acetyllactosamine residues in the backbone of their structures. Good to excellent agreement was observed between predicted and experimental H-1 and C-13 NMR chemical shifts showing the utility of the method for structural determination or confirmation of synthesized oligosaccharides.

  • 215.
    Sahoo, Suman
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Lundberg, Helena
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Edén, Mattias
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Physical Chemistry.
    Ahlsten, Nanna
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Wan, Wei
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Martín-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Single Site Supported Cationic Rhodium(I) Complexes for the Selective Redox Isomerization of Allylic Alcohols2012In: ChemCatChem, ISSN 1867-3880, E-ISSN 1867-3899, Vol. 4, no 2, p. 243-250Article in journal (Refereed)
    Abstract [en]

    The isomerization of allylic alcohols to carbonyl compounds by a heterogeneous rhodium complex is reported. Different silica material supports and catalyst/ligand systems were evaluated. The most efficient catalyst in terms of catalytic activity and stability was found to be a cationic rhodium(I) complex with sulfonated phosphine ligands anchored on a mesoporous aluminosilica AlSBA-15. The heterogeneous complex catalyzed the isomerization of a variety of allylic alcohols in excellent yields with very low catalyst loadings (0.5 mol %). The catalyst could be recycled without significant loss of activity or selectivity. The optimized catalyst was characterized by N2 sorption, powder X-ray diffraction, transmission electron microscopy, as well as solution and solid-state nuclear magnetic resonance, and Fourier Transform infrared spectroscopies.

  • 216.
    Samec, Joseph S M
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ruthenium-catalyzed hydrogen transfer involving amines and imines: Mechanistic studies and synthetic applications2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis deals with ruthenium-catalyzed hydrogen transfer involving amines and imines and is divided into two parts.

    In Part 1 a mechanistic study has been performed. The complexation of the imine to the catalyst and the decomplexation patterns of the formed ruthenium-amine complexes, isotope studies, and exchange studies show that the mechanism of the hydrogen transfer involving amines and imines is different from the hydrogen transfer involving alcohols and carbonyls.

    In Part 2 synthetic applications of the hydrogen transfer is presented. First the rutheniumcatalyzed transfer hydrogenation of imines by 2-propanol in an unpolar solvent was investigated. The corresponding amines were isolated in good to excellent yields. Even imines bearing labile functional groups were smoothly transferred to amines with very low catalyst loadings and short reaction times employing microwave heating. Then the reverse reaction, transfer dehydrogenation of amines to imines, was investigated using either MnO2 or oxygen as terminal oxidant. Important products such as aldimines, ketimines, and non benzylic anilines were prepared in the aerobic oxidation. We also demonstrated that the aerobic oxidation is compatible with proline-mediated organocatalysis, yielding amines in high yields and ee:s. Finally the racemization of chiral amines was investigated. A cumbersome side product formation was investigated and hampered by the use of a mild hydrogen donor, giving a mild and efficient racemization process for both primary and secondary amines.

  • 217.
    Sandström, Anders G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Protein Engineering of Candida antarctica Lipase A: Enhancing Enzyme Properties by Evolutionary and Semi-Rational Methods2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Enzymes are gaining increasing importance as catalysts for selective transformations in organic synthetic chemistry. The engineering and design of enzymes is a developing, growing research field that is employed in biocatalysis. In the present thesis, combinatorial protein engineering methods are applied for the development of Candida antarctica lipase A (CALA) variants with broader substrate scope and increased enantioselectivity. Initially, the structure of CALA was deduced by manual modelling and later the structure was established by X-ray crystallography. The elucidation of the structure of CALA revealed several biocatalytically interesting features. With the knowledge derived from the enzyme structure, enzyme variants were produced via iterative saturation mutagenesis (ISM), a powerful protein engineering approach. Several of these variants were highly active and enantioselective towards bulky esters. Furthermore, an extensively combinatorial protein engineering approach was developed and investigated. A CALA variant with a spacious substrate binding pocket that can accommodate an unusually bulky substrate, an ester derivate of the non-steroidal anti-inflammatory drug (S)-ibuprofen, was obtained with this approach.

  • 218.
    Sandström, Anders G.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Wikmark, Ylva
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Engström, Karin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nyhlén, Jonas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Combinatorial reshaping of the Candida antarctica lipase A substrate pocket for enantioselectivity using an extremely condensed library2012In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 109, no 1, p. 78-83Article in journal (Refereed)
    Abstract [en]

    A highly combinatorial structure-based protein engineering method for obtaining enantioselectivity is reported that results in a thorough modification of the substrate binding pocket of Candida antarctica lipase A (CALA). Nine amino acid residues surrounding the entire pocket were simultaneously mutated, contributing to a reshaping of the substrate pocket to give increased enantioselectivity and activity for a sterically demanding substrate. This approach seems to be powerful for developing enantioselectivity when a complete reshaping of the active site is required. Screening toward ibuprofen ester 1, a substrate for which previously used methods had failed, gave variants with a significantly increased enantioselectivity and activity. Wild-type CALA has a moderate activity with an E value of only 3.4 toward this substrate. The best variant had an E value of 100 and it also displayed a high activity. The variation at each mutated position was highly reduced, comprising only the wild type and an alternative residue, preferably a smaller one with similar properties. These minimal binary variations allow for an extremely condensed protein library. With this highly combinatorial method synergistic effects are accounted for and the protein fitness landscape is explored efficiently.

  • 219. Sapu, Chicco Manzuna
    et al.
    Görbe, Tamás
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lihammar, Richard
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Deska, Jan
    Migratory Dynamic Kinetic Resolution of Carbocyclic Allylic Alcohols2014In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 16, no 22, p. 5952-5955Article in journal (Refereed)
    Abstract [en]

    A novel migratory dynamic kinetic resolution based on the interplay between an enzyme acylation catalyst and a heterogeneous Bronsted acid as an isomerization/racemization catalyst gives rise to carbocyclic allylic esters with excellent stereoselectivity from readily available tertiary carbinols. An easy-to-use teabag setup combining resin-bound catalysts, a biphasic isooctanewater solvent system, and a highly lipophilic acyl donor efficiently suppresses side reactions and allows for the preparation of functionalized carbocyclic building blocks in high yields and optical purity.

  • 220.
    Sebelius, Sara
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium-Catalyzed Synthesis and Transformation of Organoboranes2006Doctoral thesis, monograph (Other academic)
    Abstract [en]

    This thesis presents the development of new palladium-catalyzed transformations involving synthesis and application of allylborane reagents. In these reactions various palladium sources, including pincer complexes and commonly used catalysts were applied.

    A new transformation for allylation of aldehyde and imine substrates was devised using allyl acetates, diboronate reagents and catalytic amounts of Pd2(dba)3. By employment of commercially available chiral diboronates enantioenriched homoallyl alcohols could be obtained.

    We have also developed a palladium-catalyzed method for synthesis of functionalized allylboronic acids from vinyl cyclopropane, vinyl aziridine, allyl acetate and allyl alcohol substrates using diboronic acid as reagent. In this process a highly selective selenium based pincer-complex was used as catalyst. The resulting allylboronic acid products were converted to potassium trifluoro(allyl)borates or allylboronates.

    The functionalized allylboronic acids generated in the above procedure were employed as reagents in two synthetic transformations. One of these transformations involves a palladium(0)-catalyzed coupling reaction between allylboronic acids and aryl iodides. The reaction was regioselective for the branched allylic product, typically difficult to prepare in the absence of directing groups. We also developed another transformation for allylation of aldehydes with allyl alcohols via allylboronic acid intermediate. This procedure can be performed as a simple one-pot sequence affording homoallyl alcohols with excellent stereo- and regioselectivity.

  • 221.
    Sebelius, Sara
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kálmán J., Szabó
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Allylation of aldehyde and imine substrates with in situ generated allylboronates - a simple route to enantioenriched homoallyl alcohols2005In: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, no 12, p. 2539-2547Article in journal (Refereed)
    Abstract [en]

    Allylation of aldehyde and imine substrates was achieved using easily available allylacetates and diboronate reagents in the presence of catalytic amounts of palladium. This operationally simple one-pot reaction has a broad synthetic scope, as many functionalities including, acetate, carbethoxy, amido and nitro groups are tolerated. The allylation reactions proceed with excellent regio- and stereoselectivity affording the branched allylic isomer. By employment of commercially available chiral diboronates enantioenriched homoallyl alcohols (up to 53% ee) could be obtained. The mechanistic studies revealed that the in situ generated allylboronates react directly with the aldehyde substrates, however the allylation of the sulfonylimine substrate requires palladium catalysis.

  • 222.
    Selander, Nicklas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Catalytic Functionalization of Allylic Substrates by Palladium Pincer Complexes2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is based on the development of novel catalytic reactions for the synthesis and application of organometallic reagents. The main focus is directed towards organoboronate derivatives. We developed an efficient procedure for converting allylic alcohols to the corresponding allylboronates using palladium pincer complexes as catalysts. The reactions were performed under mild conditions with high selectivity, allowing further one-pot transformations. Using this approach, a variety of stereodefined homoallylic alcohols and amino acid derivatives were synthesized via trapping of the in situ generated allylboronate derivatives with an appropriate electrophile. The synthetic scope of these types of multi-component reactions is broad as many different substrate allylic alcohols may be used together with various electrophiles. Several aspects of these reactions were studied, including different reagents, catalysts and electrophiles.

    Furthermore, we studied the possibility to use oxidizing reagents as an essential component in the functionalization of olefins. Two main strategies were utilized for these catalytic methods using palladium pincer complexes. The functional group was either transferred from the oxidizing reagent, or introduced via an oxidation-transmetallation route. We propose that both methods involve palladium(IV) intermediates thus expanding both the coordination sphere of palladium and the synthetic scope of pincer complex catalysis.

  • 223.
    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.

  • 224. Shashkov, Alexander S.
    et al.
    Wang, Tianwei
    Perepelov, Andrei V.
    Weintraub, Andrej
    Liu, Bin
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Knirel, Yuriy A.
    Structure elucidation and biosynthesis gene cluster organization of the O-antigen of Escherichia coli O1702015In: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 417, p. 11-14Article in journal (Refereed)
    Abstract [en]

    Enterotoxigenic Escherichia coli are causative agents of diarrhea in humans as well as animals, and E. coli O170 belongs to this virotype. Upon mild acid degradation of the lipopolysaccharide of E. coli O170, the branched O-polysaccharide chain was partially cleaved at beta-D-glactofuranosidic linkages to give multiple products, including a linear tetrasaccharide and oligomers thereof. Studies of the acid degradation products and O-deacylated lipopolysaccharide by 1D and 2D H-1 and C-13 NMR spectroscopy enabled elucidation of the following O-polysaccharide structure: -> 4)-beta-D-GlcpNAc-(1 -> 4)-beta-D-GlcpA-(1 -> 3)-beta-D-Galf-(1 -> 3)-beta-D-GlcNAc-(1 -> [GRAPHICS] beta-D-Galf Functions of genes in the O-antigen biosynthesis gene cluster were tentatively assigned and found to be in agreement with the O-polysaccharide structure.

  • 225. Shashkov, Alexander S.
    et al.
    Zhang, Wenwen
    Perepelov, Andrei V.
    Weintraub, Andrej
    Liu, Bin
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Knirel, Yuriy A.
    Structure of the O-polysaccharide of Escherichia coli O1322016In: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 427, p. 44-47Article in journal (Refereed)
    Abstract [en]

    Mild acid degradation of the lipopolysaccharide of Escherichia coli O132 released its O-polysaccharide. Analysis by 1D and 2D H-1 and C-13 NMR spectroscopy prior and subsequent to O-deacetylation, in conjunction with sugar analysis, revealed a linear pentasaccharide repeating unit of the O-polysaccharide having the following structure: -> 2)-alpha-D-Galf-(1 -> 3)-alpha-L-Rhap2Ac-(1 -> 4)-alpha-D-Glcp-(1 -> 2)-alpha-L-Rhap-(1 -> 3)-beta-D-GlcpNAc-(1 -> Putative functions of genes in the O-antigen gene cluster of E. coli O132 are consistent with the O-polysaccharide structure.

  • 226.
    Shatskiy, Andrey
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ru-Based Water Oxidation Catalysts: Development and Mechanistic Studies2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Oxidation of water constitutes one of the most challenging processes in artificial photosynthesis, which aims at storing solar energy in the form of chemical bonds of high-energy fuels. To facilitate this process, efficient and durable water oxidation catalysts have to be developed and integrated into the complete photosynthetic cells. Importantly, the intricate complexity of such devices requires the catalyst not only to be highly efficient and robust, but also operate through a well-defined mechanism.

    This thesis describes the development and mechanistic studies of new water oxidation catalysts based on ruthenium. The first part of the thesis describes the synthesis of a dinuclear ruthenium-based catalyst active for both chemical and light-driven water oxidation. This catalyst displayed a pronounced influence of the acetonitrile co-solvent on the redox properties, which was studied in detail by electrochemical methods. In the second part, a new benzimidazole-based mononuclear catalyst was evaluated. The activity of the catalyst was studied for chemical and light-driven water oxidation, and insight into the operating mechanism was provided with the help of density functional theory calculations. In the third part of the thesis, a new mononuclear ruthenium-based catalyst was prepared and evaluated for electrochemically-driven water oxidation. This catalyst displayed activity similar to that of the current state-of-the-art water oxidation catalyst, while eliminating its main drawback, that is incomplete activation. The redox properties of the new catalyst were studied in detail by electrochemical and spectroscopic techniques, providing insight into the origins of its improved performance. Finally, in the fourth part of the thesis, a heterogeneous nanoparticulate catalyst immobilized on a solid support is described. The catalyst displayed high activity and stability during chemical and light-driven water oxidation, which was attributed to the small average particle size and efficient anchoring of the catalyst to the heterogeneous support via an oxidatively-stable linker.

  • 227. Siegbahn, Anna
    et al.
    Manner, Sophie
    Persson, Andrea
    Tykesson, Emil
    Holmqvist, Karin
    Ochocinska, Agata
    Rönnols, Jerk
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sundin, Anders
    Mani, Katrin
    Westergren-Thorsson, Gunilla
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ellervik, Ulf
    Rules for priming and inhibition of glycosaminoglycan biosynthesis; probing the beta 4GalT7 active site2014In: Chemical Science, ISSN 2041-6520, E-ISSN 2041-6539, Vol. 5, no 9, p. 3501-3508Article in journal (Refereed)
    Abstract [en]

    beta-1,4-Gatactosyltransferase 7 (beta 4GalT7) is an essential enzyme in the biosynthesis of glycosaminoglycan (GAG) chains of proteoglycans (PGs). Mammalian cells produce PGs, which are involved in biological processes such as cell growth and differentiation. The PGs consist of a core protein, with one or several GAG chains attached. Both the structure of the PGs and the GAG chains, and the expression of the enzymes involved in their biosynthesis and degradation, vary between normal cells and tumor cells. The biosynthesis of GAG chains is initiated by xylosylation of a serine residue of the core protein, followed by galactosylation by beta 4GalT7. The biosynthesis can also be initiated by exogenously added beta-D-xylopyranosides with hydrophobic aglycons, which thus can act as acceptor substrates for beta 4GalT7. To determine the structural requirements for beta 4GalT7 activity, we have cloned and expressed the enzyme and designed a focused library of 2-naphthyl beta-D-xylopyranosides with modifications of the xylose moiety. Based on enzymatic studies, that is galactosylation and its inhibition, conformational analysis and molecular modeling using the crystal structure, we propose that the binding pocket of beta 4GalT7 is very narrow, with a precise set of important hydrogen bonds. Xylose appears to be the optimal acceptor substrate for galactosylation by beta 4GalT7. However, we show that modifications of the xylose moiety of the beta-D-xylopyranosides can render inhibitors of galactosylation. Such compounds will be valuable tools for the exploration of GAG and PG biosynthesis and a starting point for development of anti-tumor agents.

  • 228. Siegbahn, Anna
    et al.
    Thorsheim, Karin
    Ståhle, Jonas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Manner, Sophie
    Hamark, Christoffer
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Persson, Andrea
    Tykesson, Emil
    Mani, Katrin
    Westergren-Thorsson, Gunilla
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ellervik, Ulf
    Exploration of the active site of beta 4GalT7: modifications of the aglycon of aromatic xylosides2015In: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 13, no 11, p. 3351-3362Article in journal (Refereed)
    Abstract [en]

    Proteoglycans (PGs) are macromolecules that consist of long linear polysaccharides, glycosaminoglycan (GAG) chains, covalently attached to a core protein by the carbohydrate xylose. The biosynthesis of GAG chains is initiated by xylosylation of the core protein followed by galactosylation by the galactosyltransferase beta 4GalT7. Some beta-D-xylosides, such as 2-naphthyl beta-D-xylopyranoside, can induce GAG synthesis by serving as acceptor substrates for beta 4GalT7 and by that also compete with the GAG synthesis on core proteins. Here we present structure-activity relationships for beta 4GalT7 and xylosides with modifications of the aromatic aglycon, using enzymatic assays, cell studies, and molecular docking simulations. The results show that the aglycons reside on the outside of the active site of the enzyme and that quite bulky aglycons are accepted. By separating the aromatic aglycon from the xylose moiety by linkers, a trend towards increased galactosylation with increased linker length is observed. The galactosylation is influenced by the identity and position of substituents in the aromatic framework, and generally, only xylosides with beta-glycosidic linkages function as good substrates for beta 4GalT7. We also show that the galactosylation ability of a xyloside is increased by replacing the anomeric oxygen with sulfur, but decreased by replacing it with carbon. Finally, we propose that reaction kinetics of galactosylation by beta 4GalT7 is dependent on subtle differences in orientation of the xylose moiety.

  • 229. Silva, Luiz F., Jr.
    et al.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hypervalent iodine reagents in the total synthesis of natural products2011In: Natural product reports (Print), ISSN 0265-0568, E-ISSN 1460-4752, Vol. 28, no 10, p. 1722-1754Article, review/survey (Refereed)
    Abstract [en]

    This report describes the recent applications of hypervalent iodine reagents in the total synthesis of natural products. The large diversity of high-yielding and chemoselective reactions that can be achieved, even for highly functionalized molecules, is summarized, demonstrating that hypervalent iodine reagents have become an essential tool in synthetic organic chemistry.

  • 230. Siqueira, Fernanda A.
    et al.
    Ishikawa, Eloisa E.
    Fogaça, André
    Faccio, Andréa T.
    Carneiro, Vânia M. T.
    Soares, Rafael R. S.
    Utaka, Aline
    Tébéka, Iris R. M.
    Bielawski, Marcin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Silva Jr., Luiz F.
    Metal-Free Synthesis of Indanes by Iodine(III)-Mediated Ring Contraction of 1,2-Dihydronaphthalenes2011In: Journal of the Brazilian Chemical Society, ISSN 0103-5053, E-ISSN 1678-4790, Vol. 22, no 9, p. 1795-1807Article in journal (Refereed)
    Abstract [en]

    A metal-free protocol was developed to synthesize indanes by ring contraction of 1,2-dihydronaphthalenes promoted by PhI(OH)OTs (HTIB or Koser’s reagent). This oxidative rearrangement can be performed in several solvents (MeOH, CH3CN, 2,2,2-trifluoroethanol (TFE), 1,1,1,3,3,3-hexafluoroisopropanol (HFIP), and a 1:4 mixture of TFE:CH2Cl2) under mild conditions. The ring contraction diastereoselectively gives functionalized trans-1,3-disubstituted indanes, which are difficult to obtain in synthetic organic chemistry.

  • 231.
    Slagbrand, Tove
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Development and Applications of Molybdenum-Catalyzed Chemoselective Amide Reduction2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis covers the development of catalytic methodologies for the mild and chemoselective hydrosilylation of amides. The first part describes the investigation of the Mo(CO)6-catalyzed reduction of carboxamides. It was found that the reduction could be controlled by tuning the reaction temperature and either amines or aldehydes could be obtained selectively. The system showed an unprecedented chemoselectivity and the amide reduction could take place in the presence of other reducible functional groups such as ketones, aldehydes, and imines. Moreover, the transformation could be performed on a preparative scale and was further employed in the synthesis of Donepezil, a pharmaceutical drug used in the treatment of Alzheimer´s disease.

    The third chapter concerns the development of the Mo(CO)6-mediated hydrosilylation protocol for the reduction of carboxamides containing acidic α-hydrogens. In this case, enamines were formed and a high level of chemoselectivity was observed. Enamines containing sensitive functional groups such as ketones, aldehydes and imines were generated. The enamines were not isolated but used in subsequent catalytic reductive functionalization of amides, which is described in the last part of the thesis (Chapters 4 – 7). The in situ formed enamines were reacted with a wide variety of electrophiles, generating heterocyclic compounds as triazolines, triazoles, 4,5-dihydroisoxazoles and pyrimidinediones. N-sulfonylformamidines as well as thioacrylamides could also be prepared with this approach. The protocols for the synthesis of triazolines, triazoles and N-sulfonylformamidines could additionally be performed on a preparative scale, showing the practicality of the methodology.

  • 232.
    Slättegård, Rikard
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of Structures Related to the Capsular Polysaccharide of Neisseria meningitidis Serogroup A and to Mycothiol2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

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

  • 233.
    Stewart, Beverly
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nyhlén, Jonas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martin-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Privalov, Timofei
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    A computational study of the CO dissociation in cyclopentadienyl ruthenium complexes relevant to the racemization of alcohols2013In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 42, no 4, p. 927-934Article in journal (Refereed)
    Abstract [en]

    The formation of an active 16-electron ruthenium sec-alkoxide complex via loss of the CO ligand is an important step in the mechanism of the racemization of sec-alcohols by (eta(5)-Ph5C5) Ru(CO)(2)X ruthenium complexes with X = Cl and OtBu. Here we show with accurate DFT calculations the potential energy profile of the CO dissociation pathway for a series of relevant (eta(5)-Ph5C5) Ru(CO) 2X complexes, where X = Cl, OtBu, H and (COOBu)-Bu-t. We have found that the CO dissociation energy increases in the following order: OtBu (lowest), Cl, COOtBu and H (highest). Using the distance between ruthenium and C-CO, r = Ru-C-CO, as a constraint, and by optimizing all other degrees of freedom for a range of Ru-CO distances, we obtained relative energies, Delta E(r) and geometries of a sufficient number of transient structures with the elongated Ru-CO bond up to r = 3.4 angstrom. Our calculations provide a quantitative understanding of the CO ligand dissociation in (eta(5)-Ph5C5) Ru(CO)(2)Cl and (eta(5)-Ph5C5) Ru(CO) 2(OtBu) complexes, which is relevant to the mechanism of their catalytic activity in the racemization of alcohols. We recently reported that exchange of the CO ligand by isotopically labeled (CO)-C-13 in the Ru-(OBu)-Bu-t complex occurs twenty times faster than that in the Ru-Cl complex. This corresponds to a difference of 1.8 kcal mol(-1) in the CO dissociation energy (at room temperature). This is in very good agreement with the calculated difference between the two potential energy curves for Ru-OtBu and Ru-Cl complexes, which is about 1.8-2 kcal mol(-1) around the corresponding transition states of the CO dissociation. The calculated difference in the total energy for CO dissociation in (eta(5)-Ph5C5) Ru(CO)(2)X complexes is related to the stabilization provided by the X group in the final 16-electron complexes, which are formed via product-like transition states. In addition to the calculated transition states of CO dissociation in Ru-OtBu and Ru-Cl complexes, the calculated transient structures with the elongated Ru-CO bond provide insight into how the geometry of the ruthenium complex with a potent heteroatom donor group (X) gradually changes when one of the COs is dissociating.

  • 234.
    Stridfeldt, Elin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hypervalent Iodine Reagents in Metal-Free Arylations and Vinylations: Investigation of Suitable Coupling Partners and Synthesis of New Reagents2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis concerns the development of metal-free reactions to obtain carbon-heteroatom and carbon-carbon bonds. This is achieved by transferring carbon ligands from hypervalent iodine reagents to suitable nucleophiles.

    The bulk of the work presented herein concerns arylation of oxygen and nitrogen nucleophiles, using the well-known diaryliodonium salts as aryl sources. In the first project, O-arylation of the oxime ethyl acetohydroxamate was studied. It was found that electron-poor as well as electron-rich aryl moieties could be transferred successfully to this nucleophile. Furthermore, the protocol could be extended to a sequential one-pot synthesis of benzo[b]furans. This method allowed for a fast synthesis of the natural product stemofuran A and formal syntheses of other natural products.

    In a successive project, O-arylation of hydroxide and aliphatic alkoxides was investigated. It is known that electron-poor aryl moieties can be transferred to these nucleophiles in moderate to high yields. However, combined with more electron-rich diaryliodonium salts, a large amount of side products were formed. These were suppressed upon addition of aryne traps, suggesting that aryne pathways are competing with the desired ligand coupling. It was also observed that secondary alcohols were oxidized to the corresponding ketones. The mechanism for this oxidation was investigated and aryne pathways could be excluded. Instead we suggest that the carbinol hydrogen gets deprotonated via an internal mechanism, after the alkoxide has coordinated to the iodonium salt. Highly sterically congested alkyl aryl ethers could be obtained in high yields by combining tertiary alcohols with ortho-blocked diaryliodonium salts. 

    Next, N-arylation of secondary acyclic amides was studied using acetanilide as the model substrate. This procedure was suitable for transfer of electron-poor as well as ortho-substituted aryl moieties, but attempts to transfer very electron-rich aryl groups were unsuccessful. On the other hand, the amides displayed a complementary reactivity, allowing phenylation of electron-rich amides. 

    In the final project, a one-pot synthesis of the cyclic iodonium reagent vinylbenziodoxolone is presented. These compounds have not been explored as reagents earlier. Initial screenings showed that the vinyl moiety could be transferred to nitrocyclohexane with opposite regioselectivity compared to the acyclic analogue of the reagent.

  • 235.
    Stridfeldt, Elin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lindstedt, Erik
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Reitti, Marcus
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Blid, Jan
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Norrby, Per-Ola
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Competing Pathways in O-Arylations with Diaryliodonium Salts: Mechanistic Insights2017In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, no 53, p. 13249-13258Article in journal (Refereed)
    Abstract [en]

    A mechanistic study of arylations of aliphatic alcohols and hydroxide with diaryliodonium salts, to give alkyl aryl ethers and diaryl ethers, has been performed using experimental techniques and DFT calculations. Aryne intermediates have been trapped, and additives to avoid by-product formation originating from arynes have been found. An alcohol oxidation pathway was observed in parallel to arylation; this is suggested to proceed by an intramolecular mechanism. Product formation pathways via ligand coupling and arynes have been compared, and 4-coordinated transition states were found to be favored in reactions with alcohols. Furthermore, a novel, direct nucleophilic substitution pathway has been identified in reactions with electron-deficient diaryliodonium salts.

  • 236.
    Ståhle, Jonas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Structure Elucidations of Bacterial Polysaccharides using NMR Spectroscopy and Bioinformatics2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Carbohydrates are ubiquitous components in nature involved in a range of tasks. They cover every cell and contribute both structural stability as well as identity. Lipopolysaccharides are the outermost exposed part of the bacterial cell wall and the primary target for host-pathogen recognition. Understanding the structure and biosynthesis of these polysaccharides is crucial to combat disease and develop new medicine. Structural determinations can be carried out using NMR spectroscopy, a powerful tool giving information on an atomistic scale. This thesis is focused on method development to study polysaccharide structures as well as application on bacterial lipopolysaccharides. The focus has been to incorporate a bioinformatics approach prior to analysis by NMR spectroscopy, and then computer assisted methods to aid in the subsequent analysis of the spectra.

    The third chapter deals with the recent developments of ECODAB, a tool that can help predict structural fragments in Escherichia coli O-antigens. It was migrated to a relational database and the aforementioned predictions can now be made automatically by ECODAB. The fourth chapter gives insight into the program CASPER, a computer program that helps with structure determination of oligo- and polysaccharides. An approach to determine substituent positions in polysaccharides was investigated. The underlying database was also expanded and the improved capabilities were demonstrated by determining O-antigenic structures that could not previously be solved. The fifth chapter is an application to O‑antigen structures of E. coli strains. This is done by a combination of NMR spectroscopy and bioinformatics to predict components as well as linkages prior to spectra analysis. In the first case, a full structure elucidation was performed on E. coli serogroup O63, and in the second case a demonstration of the bioinformatics approach is done to E. coli serogroup O93. In the sixth chapter, a new version of the CarbBuilder software is presented. This includes a more robust building algorithm that helps build sterically crowded polysaccharide structures, as well as a general expansion of possible components. 

  • 237.
    Säwén, Elin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    NMR spectroscopy and MD simulations of carbohydrates2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Knowledge about the structure, conformation and dynamics of carbohydrates is important in our understanding of the way carbohydrates function in biological systems, for example in intermolecular signaling and recognition. This thesis is a summary of five papers studying these properties in carbohydrate-containing molecules with NMR spectroscopy and molecular dynamics simulations.

    In paper I, the ring-conformations of the six-membered rings of two carbaiduronic analogs were investigated. These carbasugars could potentially be used as hydrolytically stable mimics of iduronic acid in drugs. The study showed that the equilibrium is entirely shifted towards the 4C1 conformation.

    Paper II is an investigation of the conformational flexibility and dynamics of two (1→6)-linked disaccharides related to an oligosaccharide epitope expressed on malignant tumor cells.

    In paper III, the conformational space of the glycosidic linkage of an alfa-(1→2) linked mannose disaccharide present in N- and O-linked glycoproteins, was studied. A maximum entropy analysis using different priors as background information was used and four new Karplus equations for 3JC,C and 3JC,H coupling constants, related to the glycosidic linkage, were presented.

    Paper IV describes a structural elucidation of the exopolysaccharide (EPS) produced by Streptococcus thermophilus ST1, a major dairy starter used in yoghurt and cheese production. The EPS contains a hexasaccharide repeating unit of d-galactose and d-glucose residues, which is a new EPS structure of the S. thermophilus species.

    In paper V, the dynamics of three generations of glycodendrimers were investigated by NMR diffusion and 13C NMR relaxation studies. Three different correlations times were identified, one global correlation time describing the rotation of the dendrimer as a whole, one local correlation time describing the reorientation of the C-H vectors, and one correlation time describing the pulsation of a dendrimer branch.

  • 238.
    Teodorovic, Peter
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of oligosaccharides related to the capsular polysaccharide of Neisseria meningitidis serotype A2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In order to find suitable stable vaccine candidates against Neisseria meningitidis group A, several structures related to the capsular polysaccharide have been synthesised. The first part of the thesis describes the synthesis of C-phosphonate analogues starting from glucose. The key step is a Mitsunobu coupling of a methyl C-phosphonate monomer to the 6-hydroxyl group of a 2-acetamido mannose derivative. Contained within this work is a description of an improved synthesis of 2-azido-2-deoxy-D-mannopyranose. The second part outlines the synthesis of structural elements present in the native capsular polysaccharide of Neisseria meningitidis serotype A including different acetylation and phosphorylation patterns. The final chapter describes an improved synthesis of the Lewis b hexasaccharide needed for purification of and interaction studies with the Helicobacter pylori adhesin BabA.

  • 239. Thorsheim, Karin
    et al.
    Siegbahn, Anna
    Johnsson, Richard E.
    Stalbrand, Henrik
    Manner, Sophie
    Bartholomeyzik, Teresa
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ellervik, Ulf
    Chemistry of xylopyranosides2015In: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 418, p. 65-88Article, review/survey (Refereed)
    Abstract [en]

    Xylose is one of the few monosaccharidic building blocks that are used by mammalian cells. In comparison with other monosaccharides, xylose is rather unusual and, so far, only found in two different mammalian structures, i.e. in the Notch receptor and as the linker between protein and glycosaminoglycan (GAG) chains in proteoglycans. Interestingly, simple soluble xylopyranosides can not only initiate the biosynthesis of soluble GAG chains but also function as inhibitors of important enzymes in the biosynthesis of proteoglycans. Furthermore, xylose is a major constituent of hemicellulosic xylans and thus one of the most abundant carbohydrates on Earth. Altogether, this has spurred a strong interest in xylose chemistry. The scope of this review is to describe synthesis of xylopyranosyl donors, as well as protective group chemistry, modifications, and conformational analysis of xylose.

  • 240.
    Tinnis, Fredrik
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Stridfeldt, Elin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lundberg, Helena
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Adolfsson, Hans
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Stellenbosch University, South Africa.
    Metal-Free N-Arylation of Secondary Amides at Room Temperature2015In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 17, no 11, p. 2688-2691Article in journal (Refereed)
    Abstract [en]

    The arylation of secondary acyclic amides has been achieved with diaryliodonium salts under mild and metal-free conditions. The methodology has a wide scope, allows synthesis of tertiary amides with highly congested aryl moieties, and avoids the regioselectivity problems observed in reactions with (diacetoxyiodo)benzene.

  • 241.
    Tinnis, Fredrik
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Verho, Oscar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Gustafson, Karl P. J.
    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.
    Adolfsson, Hans
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Efficient Palladium-Catalyzed Aminocarbonylation of Aryl Iodides Using Palladium Nanoparticles Dispersed on Siliceous Mesocellular Foam2014In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 20, no 20, p. 5885-5889Article in journal (Refereed)
    Abstract [en]

    A highly dispersed nanopalladium catalyst supported on mesocellular foam (MCF), was successfully used in the heterogeneous catalysis of aminocarbonylation reactions. During the preliminary evaluation of this catalyst it was discovered that the supported palladium nanoparticles exhibited a “release and catch” effect, meaning that a minor amount of the heterogeneous palladium became soluble and catalyzed the reaction, after which it re-deposited onto the support.

  • 242.
    Tolnai, Gergely L.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nilsson, Ulf J.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Efficient O-Functionalization of Carbohydrates with Electrophilic Reagents2016In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 55, no 37, p. 11226-11230Article in journal (Refereed)
    Abstract [en]

    Novel methodology for O-functionalization of carbohydrate derivatives has been established using bench-stable and easily prepared iodonium(III) reagents. Both electron-withdrawing and electron-donating aryl groups were introduced under ambient conditions and without precautions to exclude air or moisture. Furthermore, the approach was extended both to full arylation of cyclodextrin, and to trifluoroethylation of carbohydrate derivatives. This is the first general approach to introduce traditionally non-electrophilic groups into any of the OH groups around the sugar backbone. The methodology will be useful both in synthetic organic chemistry and biochemistry, as important functional groups can be incorporated under simple and robust reaction conditions in a fast and efficient manner.

  • 243.
    Tran, Lien-Hoa
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Biomimetic Reactions: Water Oxidation and Aerobic Oxidation2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis deals mainly with two oxidation reactions: water oxidation and aerobic oxidation, both of which have been applied in a biomimetic fashion. In the former reaction molecular oxygen is generated whereas in the latter it was used as terminal oxidant in oxidation reactions.

    The first part of this thesis describes the synthesis of different ruthenium and manganese complexes that could potentially act as catalysts for water oxidation. This part includes a discussion of the stability and reactivity of a new manganese(III) amide-type complex, that has been used as a catalyst for both epoxidation of stilbene and alcohol oxidation.

    The second part of this thesis discusses the synthesis of two new hybrid catalysts consisting of hydroquinone linked cobalt(II) salophen and cobalt(II) salmdpt, which have been used as oxygen-activating catalysts in aerobic oxidation reactions. The former catalyst was applied to the Pd-catalyzed reactions such as 1,4-diacetoxylation of cyclohexadiene whereas the latter was applied to the Ru-catalyzed oxidation of secondary alcohols to ketones. Moreover, these two hybrid catalysts could be used in the Pd-catalyzed carbocyclization of enallenes. In all cases molecular oxygen was used as the stoichiometric oxidant.

     

  • 244.
    Träff, Annika
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Asymmetric transformation of ß- and γ-functionalized alcohols: Study of combined ruthenium-catalyzed racemization and enzymatic resolution2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The major part of this thesis describes the asymmetric synthesis of β- and γ-amino alcohols through the combination of ruthenium catalyzed racemization and enzymatic kinetic resolution.

    The dynamic kinetic resolution, DKR, protocol for chlorohydrins was improved by employing Bäckvall’s catalyst, which is a base activated racemization catalyst, in combination with Burkholderia cepacia lipase. These optimized conditions broadened the substrate scope and improved the yields and ee’s of the obtained chlorohydrin acetates. The utility of the method was demonstrated in the synthesis of (S)-salbutamol.

    In the second part of the thesis, DKR was utilized in the enantio-determining step of the total synthesis of (R)-duloxetine. Optimized DKR conditions, combining Bäckvall’s catalyst together with Candida antarctica lipase B, afforded a β-cyano acetate in high yield and ee. (R)-Duloxetine was accessible through synthetic alterations of the enantioenriched β-cyano acetate in high overall yield.

    A dynamic kinetic asymmetric transformation, DYKAT, protocol to obtain enantio- and diastereomerically pure γ-amino alcohols was developed. In a first step N-Boc-aminoketones were obtained in high enantiomeric purity through a proline-catalyzed Mannich reaction. Subsequent in situ reduction coupled with a highly efficient DYKAT yielded γ-amino acetates in high dr and ee. The γ-amino alcohols were available through simple hydrolysis/deprotection with retained stereochemistry.

    In the final part of the thesis a heterogeneous bifunctional catalytic system is reported, which combines the catalytic properties of transition metal-catalyzed racemization with enzymatic acylation. A novel ruthenium-phosphonate complex was synthesized and then covalently anchored to the active site of solid supported Candida antarctica lipase B. The partially inhibited beads proved to be catalytically active both in racemization as well as enzymatic acylation.

  • 245. Tutkowski, Brandon
    et al.
    Kerdphon, Sutthichat
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Limé, Elaine
    Helquist, Paul
    Andersson, Pher G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Wiest, Olaf
    Norrby, Per-Ola
    Revisiting the Stereodetermining Step in Enantioselective Iridium-Catalyzed Imine Hydrogenation2018In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 8, no 1, p. 615-623Article in journal (Refereed)
    Abstract [en]

    The mechanism for the iridium-catalyzed asymmetric hydrogenation of prochiral imines has been investigated for an experimentally relevant ligand substrate combination using DFT calculations. The possible stereoisomers of the stereodetermining hydride transfer transition state were considered for four possible hydrogenation mechanisms starting from the recently disclosed active catalyst consisting of iridium phosphine-oxazoline with cyclometalated imine substrate. The hydrogenation was found to proceed via an outer sphere pathway. The transition state accurately describes the experimental observations of the active catalyst and provides a structural rationale for the high stereoinduction despite the lack of direct interaction points in the outer-sphere mechanism. The predicted enantioselectivity was consistent with experimental observations. Experimental studies support the hypothesis that the iridacycle forms spontaneously and functions as the active catalyst in the hydrogenation.

  • 246.
    Utas, Josefin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hydrogen Bonded Phenols as Models for Redox-Active Tyrosines in Enzymes2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis deals with the impact of hydrogen bonding on the properties of phenols. The possibility for tyrosine to form hydrogen bonds to other amino acids has been found to be important for its function as an electron transfer mediator in a number of important redox enzymes. This study has focused on modeling the function of tyrosine in Photosystem II, a crucial enzyme in the photosynthetic pathway of green plants.

    Hydrogen bonds between phenol and amines in both inter- and intramolecular systems have been studied with quantum chemical calculations and also in some solid-state structures involving phenol and imidazole.

    Different phenols linked to amines have been synthesized and their possibilities of forming intra- and intermolecular hydrogen bonds have been studied as well as the thermodynamics and kinetics of the generation of phenoxyl radicals via oxidation reactions.

    Since carboxylates may in principle act as hydrogen bond acceptors in a manner similar to imidazole, proton coupled electron transfer has also been studied for a few phenols intramolecularly hydrogen bonded to carboxylates with the aim to elucidate the mechanism for oxidation. Electron transfer in a new linked phenol—ruthenium(II)trisbipyridine complex was studied as well.

    The knowledge is important for the ultimate goal of the project, which is to transform solar energy into a fuel by an artificial mimic of the natural photosynthetic apparatus

  • 247.
    Utas, Josefin E.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Efficient Synthesis of 2-Substituted Imidazoles by Palladium-Catalyzed Cross-Coupling with Benzylzinc Reagents2006In: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry, ISSN 0936-5214, E-ISSN 1437-2096, no 12, p. 1965-1967Article in journal (Refereed)
    Abstract [en]

    Substituted benzylzinc reagents have been used in novel cross-coupling reactions with 2-iodo imidazoles to form compounds containing both a phenol and an imidazole moiety. The ­intramolecular hydrogen-bonding properties of these compounds were subsequently studied.

  • 248.
    van der Werf, Angela
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hribersek, Matic
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Selander, Nicklas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    N-Trifluoromethylation of Nitrosoarenes with Sodium Triflinate2017In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 19, no 9, p. 2374-2377Article in journal (Refereed)
    Abstract [en]

    A highly efficient N-trifluoromethylation of nitro-soarenes is reported. The inexpensive and convenient Langlois reagent (sodium triflinate) is employed as a Ch(3)-radical source in combination with a copper catalyst and an oxidant. N-Trifluoromethylated hychoxylamines are obtained in high yields within 1 h at room temperature. The addition of hydroquinone was found to be instrumental to prevent the formation of side products. The method is high-yielding is scalable, and displays a high functional group tolerance.

  • 249.
    van der Werf, Angela
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Selander, Nicklas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Para-Selective Halogenation of Nitrosoarenes with Copper(II) Halides2015In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 17, no 24, p. 6210-6213Article in journal (Refereed)
    Abstract [en]

    The para-selective direct bromination and chlorination of nitrosoarenes with copper(II) bromide and chloride is reported. Under mild reaction conditions, a rang of halogenated arylnitroso compounds are obtained in moderate to good yields with high regioselectivity. Additionally, the versatility of the method is demonstrated by the development of a One-pot procedure to obtain the corresponding para-halogenated aniline- and nitrobenzene derivatives.

  • 250.
    Vazquez-Romero, Ana
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bermejo Gómez, Antonio
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martín-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Acid- and Iridium-Catalyzed Tandem 1,3-Transposition/3,1-Hydrogen Shift/Chlorination of Allylic Alcohols2015In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 5, no 2, p. 708-714Article in journal (Refereed)
    Abstract [en]

    A method for the selective synthesis of alpha-chlorocarbonyls from allylic alcohols is presented. The reaction occurs through an acid- and iridium-catalyzed tandem process that combines a 1,3-transposition, a 3,1-hydrogen shift, and a chlorination process, and can be applied to a wide range of alpha-aromatic and heteroaromatic secondary allylic alcohols. Saturated non-chlorinated ketones or other side-products derived from overchlorination were not detected.

23456 201 - 250 of 281
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