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  • 201.
    Buitrago, Elina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Lundberg, Helena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Andersson, Hans
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Ryberg, Per
    Aztra Zeneca, Global Process R&D, Södertälje, Sweden.
    Adolfsson, Hans
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Selective reduction of heteroaromatic ketones: A combinatorial approach2011Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The enantioselective reduction of prochiral ketones is a most productiveway towards enantio enriched secondary alcohols used in the preparation of biologically active compounds. There are numerous transition metal catalyzed methods for this transformation, particularly based on Ru(II)-and Rh(I)-complexes, but there is a demand for a larger substrate scope. Heteroaromatic ketones are traditionally more challenging substrates. Normally a catalyst is developed for one benchmark substrate, and asubstrate screen is made with the best performing catalyst. Using this methodology, there is a high probability that for different substrates, another catalyst could outperform the one used. We have executed a multiple screen, containing a variety of different ligands together with both Ru and Rh, and heteroaromatic ketones to fine-tune, and find the optimum catalyst depending on the substrate. The acquired information was used to synthesize known, biologically active compounds, where the key reduction steps were performed with high enantioselectivities and yields.

  • 202.
    Buitrago, Elina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Tinnis, Fredrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Adolfsson, Hans
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Efficient and Selective Hydrosilylation of Carbonyls Catalyzed by Iron Acetate and N-Hydroxyethylimidazolium Salts2012Ingår i: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 354, nr 1, s. 217-222Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Aromatic aldehydes, along with aryl alkyl, heteroaryl alkyl, and dialkyl ketones were efficiently reduced to their corresponding primary and secondary alcohols, respectively, in high yields, using the commercially available and inexpensive polymeric silane, polymethylhydrosiloxane (PMHS), as reducing agent. The reaction is catalyzed by in situ generated iron complexes containing hydroxyethyl-functionalized NHC ligands. Turnover frequencies up to 600 h−1 were obtained

  • 203.
    Buitrago, Elina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Zani, Lorenzo
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Adolfsson, Hans
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Fe/NHC-catalyzed hydrosilylation of aromatic ketones2009Ingår i: Abstracts of Papers, 238th ACS National Meeting, Washington, DC, United States, August 16-20, 2009, Washington, DC: American Chemical Society , 2009Konferensbidrag (Övrigt vetenskapligt)
  • 204.
    Buitrago, Elina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Zani, Lorenzo
    Adolfsson, Hans
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Selective hydrosilylation of ketones catalyzed by in situ-generated iron NHC complexes2011Ingår i: Applied organometallic chemistry, ISSN 0268-2605, E-ISSN 1099-0739, Vol. 25, nr 10, s. 748-752Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Aryl alkyl-, heteroaryl alkyl- and dialkyl ketones were readily reduced to their corresponding secondary alcohols in high yields, using the commercially available and inexpensive polymeric silane polymethylhydrosiloxane (PMHS), as reducing agent. The reaction is catalyzed by an in situ-generated iron complex, conveniently generated from iron(II) acetate and the commercially available N-heterocyclic carbene (NHC) precursor IPr·HCl.

  • 205.
    Bunrit, Anon
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi. Stockholm University.
    Direct Catalytic Nucleophilic Substitution of Non-Derivatized Alcohols2017Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This thesis focuses on the development of methods for the activation of the hydroxyl group in non-derivatized alcohols in substitution reactions. The thesis is divided into two parts, describing three different catalytic systems.

    The first part of the thesis (Chapter 2) describes nucleophilic allylation of amines with allylic alcohols, using a palladium catalyst to generate unsymmetrical diallylated amines. The corresponding amines were further transformed by a one-pot ring-closing metathesis and aromatization reaction to afford β-substituted pyrroles with linear and branched alkyl, benzyl, and aryl groups in overall moderate to good yields.

    The second part (Chapters 3 and 4) describes the direct intramolecular stereospecific nucleophilic substitution of the hydroxyl group in enantioenriched alcohols by Lewis acid and Brønsted acid/base catalysis.

    In Chapter 3, the direct intramolecular substitution of non-derivatized alcohols has been developed using Fe(OTf)3 as catalyst. The hydroxyl groups of aryl, allyl, and alkyl alcohols were substituted by the attack of O- and N-centered nucleophiles, to provide five- and six-membered heterocycles in up to excellent yields with high enantiospecificities. Experimental studies showed that the reaction follows first-order dependence with respect to the catalyst, the internal nucleophile, and the internal electrophile of the substrate. Competition and catalyst-substrate interaction experiments demonstrated that this transformation proceeds via an SN2-type reaction pathway.

    In Chapter 4, a Brønsted acid/base catalyzed intramolecular substitution of non-derivatized alcohols was developed. The direct intramolecular and stereospecific substitution of different alcohols was successfully catalyzed by phosphinic acid (H3PO2). The hydroxyl groups of aryl, allyl, propargyl, and alkyl alcohols were substituted by O-, N-, and S-centered nucleophiles to generate five- and six-membered heterocycles in good to excellent yields with high enantiospecificities. Mechanistic studies (both experiments and density functional theory calculations) have been performed on the reaction forming five-membered heterocyclic compounds. Experimental studies showed that phosphinic acid does not promote SN1 reactivity. Rate-order determination indicated that the reaction follows first-order dependence with respect to the catalyst, the internal nucleophile, and the internal electrophile. DFT calculations corroborated with a reaction pathway in which the phosphinic acid has a dual activation mode and operates as a bifunctional Brønsted acid/Brønsted base to simultaneously activate both the nucleophile and nucleofuge, resulting in a unique bridging transition state in an SN2-type reaction mechanism.

  • 206. Bunrit, Anon
    et al.
    Dahlstrand, Christian
    Olsson, Sandra K.
    Srifa, Pemikar
    Huang, Genping
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Orthaber, Andreas
    Sjöberg, Per J. R.
    Biswas, Srijit
    Himo, Fahmi
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Samec, Joseph S. M.
    Brønsted Acid-Catalyzed Intramolecular Nucleophilic Substitution of the Hydroxyl Group in Stereogenic Alcohols with Chirality Transfer2015Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 137, nr 14, s. 4646-4649Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The hydroxyl group of enantioenriched benzyl, propargyl, allyl, and alkyl alcohols has been intramolecularly displaced by uncharged O-, N-, and S-centered nucleophiles to yield enantioenriched tetrahydrofuran, pyrrolidine, and tetrahydrothiophene derivatives with phosphinic acid catalysis. The five-membered heterocyclic products are generated in good to excellent yields, with high degree of chirality transfer, and water as the only side-product. Racemization experiments show that phosphinic acid does not promote S(N)1 reactivity. Density functional theory calculations corroborate a reaction pathway where the phosphinic acid operates as a bifunctional catalyst in the intramolecular substitution reaction. In this mechanism, the acidic proton of the phosphinic acid protonates the hydroxyl group, enhancing the leaving group ability. Simultaneously, the oxo group of phosphinic acid operates as a base abstracting the nucleophilic proton and thus enhancing the nucleophilicity. This reaction will open up new atom efficient techniques that enable alcohols to be used as nucleofuges in substitution reactions in the future.

  • 207. Bunrit, Anon
    et al.
    Dahlstrand, Christian
    Srifa, Pemikar
    Olsson, Sandra K.
    Huang, Genping
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi. Tianjin University, China.
    Biswas, Srijit
    Himo, Fahmi
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Samec, Joseph S. M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi. Uppsala University, Sweden.
    Nucleophilic Substitution of the Hydroxyl Group in Stereogenic Alcohols with Chirality Transfer2016Ingår i: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry, ISSN 0936-5214, E-ISSN 1437-2096, Vol. 27, nr 2, s. 173-176Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A brief overview of the development of direct substitution of the hydroxyl (OH) group of alcohols in our research group is presented. By applying a BrOnsted acid, an intramolecular substitution of the OH group in stereogenic alcohols with chirality transfer was achieved. Noteworthy, the intramolecular substitution has a wide scope in respect to both the nucleophile and also the nucleofuge. A mechanistic study by both experiments and DFT calculations revealed a unique reaction pathway in which the BrOnsted acid operates in a bifunctional manner to promote an S(N)2-type reaction mechanism.

  • 208.
    Bunrit, Anon
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi. Uppsala University, Sweden.
    Sawadjoon, Supaporn
    Tšupova, Svetlana
    Sjöberg, Per J. R.
    Samec, Joseph S. M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi. Uppsala University, Sweden.
    A General Route to beta-Substituted Pyrroles by Transition-Metal Catalysis2016Ingår i: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 81, nr 4, s. 1450-1460Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An atom-efficient route to pyrroles substituted in the beta-position has been achieved in four high yielding steps by a combination of Pd, Ru, and Fe catalysis with only water and ethene as side-products. The reaction is general and gives pyrroles substituted in the beta-position with linear and branched alkyl, benzyl, or aryl groups in overall good yields. The synthetic route includes a Pd-catalyzed monoallylation step of amines with substituted allylic alcohols that proceeds to yield the monoallylated products in moderate to excellent yields. In a second step, unsymmetrical diallylated aromatic amines are generated from the reaction of a second allylic alcohol with high selectivity in moderate to good yields by control of the reaction temperature. Ru-catalyzed ring-closing metathesis performed on the diallylated aromatic amines yields the pyrrolines substituted in the beta-position in excellent yields. By addition of ferric chloride to the reaction mixture, a selective aromatization to yield the corresponding pyrroles substituted in the beta-position was achieved. A reaction mechanism involving a palladium hydride, generated from insertion of palladium to O-H of an allyl alcohol, that is responsible for the C-O bond cleavage to generate the pi-allyl intermediate is proposed.

  • 209.
    Bunrit, Anon
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Srifa, Pemikar
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Dahlstrand, Christian
    Huang, Genping
    Biswas, Srijit
    Himo, Fahmi
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Watile, Rahul
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Samec, Joseph
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    H3PO2-Catalyzed Intramolecular Stereospecific Substitution of the Hydroxyl Group in Stereogenic Secondary Alcohols by N-, O-, and S-centered Nucleophiles to Generate HeterocyclesManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    The direct intramolecular stereospecific substitution of the hydroxyl group in stereogenic secondary alcohols was successfully accomplished by phosphinic acid catalysis. The hydroxyl group was displaced by O-, S-, and N-centered nucleophiles to provide enantioenriched five- and six-membered heterocycles in good to excellent yields and high enantiospecificity with water as the only by product. Mechanistic studies using both experiments and calculations have been performed. Rate order determination shows first-order dependences in catalyst, internal nucleophile, and electrophile concentrations, however, independence on external nucleophile and electrophile. Furthermore, phosphinic acid does not promote SN1 reactivity. Computational studies support a bifunctional role of the phosphinic acid in which activations of both nucleofuge and nucleophile occur in a bridging SN2-type transition state. 

  • 210.
    Bunrit, Anon
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Watile, Rahul
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Lagerspets, Emi
    Lanekoff, Ingela
    Biswas, Srijit
    Repo, Timo
    Samec, Joseph
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Iron (III)-Catalyzed Intramolecular Stereospecific Substitution of the OH Group in Stereogenic Secondary and Tertiary AlcoholsManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    We herein report a Fe(OTf)3-catalyzed stereospecific substitution of the hydroxyl (OH) group in secondary and tertiary alcohols by N-, and O-centered nucleophiles to generate synthetically precious enantioenriched pyrrolidines, tetrahydrofuran, 1,2,3,4-tetra-hydroquinolines, and chromanes. The substitution of the OH group in benzylic, allylic, and aliphatic alcohols proceed with high yields and high degree of enantiospecificity to give saturated five- and six-membered heterocyclic products and water as the only by-product. Mechanistic studies revealed that the intramolecular substitution reaction proceeds through an SN2 reaction with secondary alcohols and an SN1 reaction, comprising a tight ion pair, with tertiary alcohols giving products with inversion of configuration at the stereogenic carbon in both cases. The iron interacts with both nucleofile and nucloefuge, where the latter leads to a controlled carbon−oxygen (C–O) bond cleavage. The procedure opens up new atom efficient technique for catalytic stereospecific reactions that allow easily accessible stereogenic secondary and tertiary alcohols to be considered as substrates in substitution reactions. 

  • 211.
    Burkhardt, Anja
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Eriksson, Lars
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi, Avdelningen för strukturkemi.
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Cumpstey, Ian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    (Z)-1,2:5,6-di-O-isopropylidene-α-D-ribo-hexofuranos-3-ulose O-benzyloxime2009Ingår i: Acta Crystallographica Section E: Structure Reports Online, ISSN 1600-5368, E-ISSN 1600-5368, Vol. E65, nr Part 3, s. o633-o633Artikel i tidskrift (Refereegranskat)
  • 212. Bustelo, Emilio
    et al.
    Gushchin, Artem L.
    Fernandez-Trujillo, M. Jesus
    Basallote, Manuel G.
    Algarra, Andres G.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    On the Critical Effect of the Metal (Mo vs. W) on the [3+2] Cycloaddition Reaction of M3S4 Clusters with Alkynes: Insights from Experiment and Theory2015Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 21, nr 42, s. 14823-14833Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Whereas the cluster [Mo3S4(acac)(3)(py)(3)](+) ([1](+), acac=acetylacetonate, py=pyridine) reacts with a variety of alkynes, the cluster [W3S4(acac)(3)(py)(3)](+) ([2](+)) remains unaffected under the same conditions. The reactions of cluster [1]+ show polyphasic kinetics, and in all cases clusters bearing a bridging dithiolene moiety are formed in the first step through the concerted [3+2] cycloaddition between the C equivalent to C atoms of the alkyne and a Mo(mu-S)(2) moiety of the cluster. A computational study has been conducted to analyze the effect of the metal on these concerted [3+ 2] cycloaddition reactions. The calculations suggest that the reactions of cluster [2](+) with alkynes feature Delta G(+) values only slightly larger than its molybdenum analogue, however, the differences in the reaction free energies between both metal clusters and the same alkyne reach up to approximately 10 kcal mol(-1), therefore indicating that the differences in the reactivity are essentially thermodynamic. The activation strain model (ASM) has been used to get more insights into the critical effect of the metal center in these cycloadditions, and the results reveal that the change in reactivity is entirely explained on the basis of the differences in the interaction energies E-int between the cluster and the alkyne. Further decomposition of the E-int values through the localized molecular orbital-energy decomposition analysis (LMO-EDA) indicates that substitution of the Mo atoms in cluster [1](+) by W induces changes in the electronic structure of the cluster that result in weaker intra-and inter-fragment orbital interactions.

  • 213. Bäck, Marcus
    et al.
    Johansson, Per-Ola
    Wångsell, Fredrik
    Thorstensson, Fredrik
    Kvarnström, Ingemar
    Ayesa, Susana
    Wähling, Horst
    Pelcman, Mikael
    Jansson, Katarina
    Lindström, Stefan
    Wallberg, Hans
    Classon, Björn
    Rydergård, Christina
    Vrang, Lotta
    Hamelink, Elizabeth
    Hallberg, Anders
    Rosenquist, Åsa
    Samuelsson, Bertil
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Novel potent macrocyclic inhibitors of the hepatitis C virus NS3 protease: use of cyclopentane and cyclopentene P2-motifs2007Ingår i: Bioorganic & Medicinal Chemistry, ISSN 0968-0896, Vol. 15, nr 22, s. 7184-7202Artikel i tidskrift (Refereegranskat)
  • 214.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi. -.
    Asymmetric Catalysis via Dynamic Kinetic Resolution2007Ingår i: Asymmetric Synthesis - The Essentials, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim , 2007, s. 171-175Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    -

  • 215.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Catalytic asymmetric synthesis via combined metal and enzyme catalysis2009Ingår i: 3rd Hellenic Symposium on Organic Synthesis, October 15-17, 2009, Athens, Greece: Abstracts of papers, Athens, 2009Konferensbidrag (Övrigt vetenskapligt)
  • 216.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Modern Oxidation Methods2010Samlingsverk (redaktörskap) (Övrigt vetenskapligt)
  • 217.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Palladium- and ruthenium-catalyzed redox reactions in selective organic synthesis2009Ingår i: Abstract of LOST II Symposium in honour of Prof. Alain Krief, March 18-20, 2009, Namur, Belgium, 2009Konferensbidrag (Övrigt vetenskapligt)
  • 218.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Pd- and Ru-catalyzed redox reactions in catalysis. Application to the combination with enzyme catalysis2009Ingår i: Abstract of 42nd Jahrestreffen Deutscher Katalytiker, March 11-13, 2009, Weimar, Germany, 2009Konferensbidrag (Övrigt vetenskapligt)
  • 219.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Preface2010Ingår i: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 53, nr 13-14, s. 831-831Artikel i tidskrift (Refereegranskat)
  • 220.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Recent advances in the combination of metal and enzyme catalysis2009Ingår i: Abstract of the 10th Netherlands Catalysis and Chemistry Conference (NCCC-X), March 2-4, 2009, Noordwijkerhout, the Netherlands, 2009Konferensbidrag (Övrigt vetenskapligt)
  • 221.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Selective oxidation of amines and sulfides2010Ingår i: Modern Oxidation Methods / [ed] Jan-Erling Bäckvall, Weinheim: Wiley-VCH Verlag GmbH & Co. KGaA , 2010, 2, s. 277-313Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 222. Cadu, Alban
    et al.
    Andersson, Pher G.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi. Council for Scientific & Industrial Research (CSIR) - South Africa .
    Iridium catalysis: application of asymmetric reductive hydrogenation2013Ingår i: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 42, nr 40, s. 14345-14356Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Iridium, despite being one of the least abundant transition metals, has found several uses. N,P-ligated iridium catalysts are used to perform many highly selective reactions. These methodologies have been developed extensively over the past 15 years. More recently, the application of iridium N,P catalysts in asymmetric hydrogenation has been a focus of research to find novel applications and to expand on their current synthetic utility. The aim of this perspective is to highlight the advances made by the Andersson group.

  • 223. Cadu, Alban
    et al.
    Upadhyay, Puspesh K.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Andersson, Pher G.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi. University of Kwazulu Natal, South Africa.
    Iridium-Catalyzed Asymmetric Hydrogenation of Substituted Pyridines2013Ingår i: Asian Journal of Organic Chemistry, ISSN 2193-5807, Vol. 2, nr 12, s. 1061-1065Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Asymmetric hydrogenation of ortho-substituted pyridines catalyzed by N,P-ligated iridium is demonstrated. To facilitate this reaction, the aromaticity of the pyridines was weakened by forming N-iminopyridium ylides. The reactions give very high conversions, and after a single recrystallization, excellent ee of up to 98% was obtained. This method lends itself to the synthesis of chiral piperidine building blocks.

  • 224. Carballeira, José Daniel
    et al.
    Krumlinde, Patrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bocola, Marco
    Vogel, Andreas
    Reetz, Manfred T.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Directed evolution and axial chirality: optimization of the enantioselectivity of Pseudomonas aeruginosa lipase towards the kinetic resolution of a racemic allene2007Ingår i: Chemical Communications, ISSN 1359-7345, Vol. 20, s. 1913-1915Artikel i tidskrift (Refereegranskat)
  • 225.
    Carson, Fabian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Agrawal, Santosh
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Gustafsson, Mikaela
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Bartoszewicz, Agnieszka
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Moraga, Francisca
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Zou, Xiaodong
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Martín-Matute, Belén
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Ruthenium Complexation in an Aluminium Metal-Organic Framework and its Application in Alcohol Oxidation Catalysis2012Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 18, nr 48, s. 15337-15344Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    A ruthenium trichloride complex has been loaded into an aluminium metalorganic framework (MOF), MOF-253, by post-synthetic modification to give MOF-253-Ru. MOF-253 contains open bipyridine sites that are available to bind with the ruthenium complex. MOF-253-Ru was characterised by elemental analysis, N2 sorption and X-ray powder diffraction. This is the first time that a Ru complex has been coordinated to a MOF through post-synthetic modification and used as a heterogeneous catalyst. MOF-253-Ru catalysed the oxidation of primary and secondary alcohols, including allylic alcohols, with PhI(OAc)2 as the oxidant under very mild reaction conditions (ambient temperature to 40 degrees C). High conversions (up to >99%) were achieved in short reaction times (13 h) by using low catalyst loadings (0.5 mol% Ru). In addition, high selectivities (>90%) for aldehydes were obtained at room temperature. MOF-253-Ru can be recycled up to six times with only a moderate decrease in substrate conversion.

  • 226.
    Carson, Fabian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Martínez-Castro, Elisa
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Marcos, Rocio
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    González Miera, Greco
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Jansson, Kjell
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Zou, Xiaodong
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Martin-Matute, Belén
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Effect of the functionalisation route on a Zr-MOF with an Ir-NHC complex for catalysis2015Ingår i: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 51, nr 54, s. 10864-10867Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new iridium N-heterocyclic carbene (NHC) metallolinker has been synthesised and introduced into a metal-organic framework (MOF), for the first time, via two different routes: direct synthesis and postsynthetic exchange (PSE). The two materials were compared in terms of the Ir loading and distribution using X-ray energy dispersive spectroscopy (EDS), the local Ir structure using X-ray absorption spectroscopy (XAS) and the catalytic activity. The materials showed good activity and recyclability as catalysts for the isomerisation of an allylic alcohol.

  • 227.
    Carson, Fabian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Martínez-Castro, Elisa
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Marcos, Rocío
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    González Miera, Greco
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Jansson, Kjell
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Zou, Xiaodong
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Martín-Matute, Belén
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Introduction of an N-heterocyclic Carbene Iridium Complex into a Zirconium Metal–Organic Framework for CatalysisManuskript (preprint) (Övrigt vetenskapligt)
  • 228.
    Carson, Fabian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Pascanu, Vlad
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bermejo Gómez, Antonio
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Zhang, Yi
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Platero-Prats, Ana E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Zou, Xiaodong
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Martín-Matute, Belén
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Influence of the Base on Pd@MIL-101-NH2(Cr) as Catalyst for the Suzuki-Miyaura Cross-Coupling Reaction2015Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 21, nr 30, s. 10896-10902Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The chemical stability of metal-organic frameworks (MOFs) is a major factor preventing their use in industrial processes. Herein, it is shown that judicious choice of the base for the Suzuki-Miyaura cross-coupling reaction can avoid decomposition of the MOF catalyst Pd@MIL-101-NH2(Cr). Four bases were compared for the reaction: K2CO3, KF, Cs2CO3 and CsF. The carbonates were the most active and achieved excellent yields in shorter reaction times than the fluorides. However, powder XRD and N-2 sorption measurements showed that the MOF catalyst was degraded when carbonates were used but remained crystalline and porous with the fluorides. XANES measurements revealed that the trimeric chromium cluster of Pd@MIL-101-NH2(Cr) is still present in the degraded MOF. In addition, the different countercations of the base significantly affected the catalytic activity of the material. TEM revealed that after several catalytic runs many of the Pd nanoparticles (NPs) had migrated to the external surface of the MOF particles and formed larger aggregates. The Pd NPs were larger after catalysis with caesium bases compared to potassium bases.

  • 229. Casas, J
    et al.
    Engqvist, Magnus
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Ibrahem, I
    Kaynak, B
    Córdova, A
    Direct Amino Acid-Catalyzed Asymmetric Synthesis of Polyketide Sugars2005Ingår i: Angewandte Chemie International ed., ISSN 1433-7851, Vol. 44, nr 9, s. 1343-1345Artikel i tidskrift (Refereegranskat)
  • 230. Casillo, Angela
    et al.
    Ståhle, Jonas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Parrilli, Ermenegilda
    Sannino, Filomena
    Mitchell, Daniel E.
    Pieretti, Giuseppina
    Gibson, Matthew I.
    Marino, Gennaro
    Lanzetta, Rosa
    Parrilli, Michelangelo
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Tutino, Maria L.
    Corsaro, Maria M.
    Structural characterization of an all-aminosugar-containing capsular polysaccharide from Colwellia psychrerythraea 34H2017Ingår i: Antonie van Leeuwenhoek. International Journal of General and Molecular Microbiology, ISSN 0003-6072, E-ISSN 1572-9699, Vol. 110, nr 11, s. 1377-1387Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Colwellia psychrerythraea strain 34H, a Gram-negative bacterium isolated from Arctic marine sediments, is considered a model to study the adaptation to cold environments. Recently, we demonstrated that C. psychrerythraea 34H produces two different extracellular polysaccharides, a capsular polysaccharide and a medium released polysaccharide, which confer cryoprotection to the bacterium. In this study, we report the structure of an additional capsular polysaccharide produced by Colwellia grown at a different temperature. The structure was determined using chemical methods, and one- and two-dimensional NMR spectroscopy. The results showed a trisaccharide repeating unit made up of only amino-sugar residues: N-acetyl-galactosamine, 2,4-diacetamido-2,4,6-trideoxy-glucose (bacillosamine), and 2-acetamido-2-deoxyglucuronic acid with the following structure: -> 4)-beta-d-GlcpNAcA-(1 -> 3)-beta-d-QuipNAc4NAc-(1 -> 3)-beta-d-GalpNAc-(1 ->. The 3D model, generated in accordance with H-1,H-1-NOE NMR correlations and consisting of ten repeating units, shows a helical structure. In contrast with the other extracellular polysaccharides produced from Colwellia at 4 A degrees C, this molecule displays only a low ice recrystallization inhibition activity.

  • 231. Castro, Vasco
    et al.
    Dvinskikh, Sergey V.
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Sandström, Dick
    Maliniak, Arnold
    NMR studies of membranes composed of glycolipids and phospholipids2007Ingår i: Biochimica et Biophysica Acta, Vol. 1768, nr -, s. 2432-2437Artikel i tidskrift (Refereegranskat)
  • 232. Chassagne, Pierre
    et al.
    Fontana, Carolina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Guerreiro, Catherine
    Gauthier, Charles
    Phalipon, Armelle
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Mulard, Laurence A.
    Structural Studies of the O-Acetyl-Containing O-Antigen from a Shigella flexneri Serotype 6 Strain and Synthesis of Oligosaccharide Fragments Thereof2013Ingår i: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, nr 19, s. 4085-4106Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Extensive analysis by NMR spectroscopy of the delipidated lipopolysaccharide of Shigella flexneri serotype 6 strain MDC 2924-71 confirmed the most recently reported structure of the O-antigen repeating unit as {4)--D-GalpA-(13)--D-GalpNAc-(12)--L-Rhap3Ac/4Ac-(12)--L-Rhap-(1}, and revealed the non-stoichiometric acetylation at O-3C/4C. Input from the CASPER program helped to ascertain the fine distribution of the three possible patterns of O-acetylation. The non-O-acetylated repeating unit (ABCD) corresponded to about 2/3 of the population, while 1/4 was acetylated at O-3C (3AcCDAB), and 1/10 at O-4C (4AcCDAB). Di- to tetrasaccharides with a GalpA residue (A) at their reducing end were synthesized as their propyl glycosides following a multistep linear strategy relying on late-stage acetylation at O-3C. Thus, the 3C-O-acetylated and non-O-acetylated targets were synthesized from common protected intermediates. Rhamnosylation was most efficiently achieved by using imidate donors, including at O-4 of a benzyl galacturonate acceptor. In contrast, a thiophenyl 2-deoxy-2-trichloroacetamido-D-galactopyranoside precursor was preferred for chain elongation involving residue B. Final Pd/C-mediated deprotection ensured O-acetyl stability. All of the target molecules represent parts of the O-antigen of S. flexneri 6, a prevalent serotype. Non-O-acetylated oligosaccharides are also fragments of the Escherichia coli O147 O-antigen.

  • 233.
    Chen, Hong
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Deng, Youqian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Yu, Zhengbao
    Zhao, Huishuang
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Yao, Qingxia
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Zou, Xiaodong
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Bäckvall, Jan-E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Sun, Junliang
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    3D Open-Framework Vanadoborate as a Highly Effective Heterogeneous Pre-catalyst for the Oxidation of Alkylbenzenes2013Ingår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 25, nr 24, s. 5031-5036Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Three three-dimensional (3D) open-framework vanadoborates, denoted as SUT-6-Zn, SUT-6-Mn, and SUT-6-Ni, were synthesized using diethylenetriamine as a template. SUT-6-Zn, SUT-6-Mn, and SUT-6-Ni are isostructural and built from (VO)(12)O-6 B18O36(OH)(6) clusters bridged by ZnO5, MnO6, and NiO6 polyhedra, respectively, to form the 3D frameworks. SUT-6 is the first vanadoborate with a 3D framework. The framework follows a semiregular hxg net topology with a 2-fold interpenetrated diamond-like channel system. The amount of template used in the synthesis played an important role in the dimensionality of the resulting vanadoborate structures. A small amount of diethylenetriamine led to the formation of this first 3D vanadoborate framework, while an increased amount of diethylenetriamine resulted in vanadoborates with zero-dimensional (0D) and one-dimensional (1D) structures. SUT-6-Zn was proved to be an efficient heterogeneous precatalyst for the oxidation of alkylbenzenes.

  • 234. Chen, Mo
    et al.
    Pendrill, Robert
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Brady, John W.
    Wohlert, Jakob
    Molecular Dynamics Simulations of the Ionic Liquid 1-n-Butyl-3-Methylimidazolium Chloride and Its Binary Mixtures with Ethanol2014Ingår i: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 10, nr 10, s. 4465-4479Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Room temperature ionic liquids (ILs) of the imidazolium family have attracted much attention during the past decade for their capability to dissolve biomass. Besides experimental work, numerous compuational studies have been concerned with the physical properties of both neat ILs and their interactions with different solutes, in particular, carbohydrates. Many classical force fields designed specifically for ILs have been found to yield viscosities that are too high for the liquid state, which has been attributed to the fact that the effective charge densities are too high due to the lack of electronic polarizability. One solution to this problem has been uniform scaling of the partial charges by a scale factor in the range 0.6-0.9, depending on model. This procedure has been shown to improve the viscosity of the models, and also to positively affect other properties, such as diffusion constants and ionic conductivity. However, less attention has been paid to how this affects the overall thermodynamics of the system, and the problems it might create when the IL models are combined with other force fields (e.g., for solutes). In the present work, we employ three widely used IL force fields to simulate 1-n-buty1-3-methyl-imidazolium chloride in both the crystal and the liquid state, as well as its binary mixture with ethanol. Two approaches are used: one in which the ionic charge is retained at its full integer value and one in which the partial charges are uniformly reduced to 85%. We investigate and calculate crystal and liquid structures, molar heat capacities, heats of fusion, self-diffusion constants, ionic conductivity, and viscosity for the neat IL, and ethanol activity as a function of ethanol concentration for the binary mixture. We show that properties of the crystal are less affected by charge scaling compared to the liquid. In the liquid state, transport properties of the neat IL are generally improved by scaling, whereas values for the heat of fusion are unaffected, and results for the heat capacity are ambiguous. Neither full nor reduced charges could reproduce experimental ethanol activities for the whole range of compositions.

  • 235. Chen, Shi-Lu
    et al.
    Blomberg, Margareta R. A.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Siegbahn, Per E. M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    An investigation of possible competing mechanisms for Ni-containing methyl-coenzyme M reductase2014Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, nr 27, s. 14029-14035Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ni-containing methyl-coenzyme M reductase (MCR) is capable of catalyzing methane formation from methyl-coenzyme M (CH3-SCoM) and coenzyme B (CoB-SH), and also its reverse reaction (methane oxidation). Based on extensive experimental and theoretical investigations, it has turned out that a mechanism including an organometallic methyl-Ni(III)F-430 intermediate is inaccessible, while another mechanism involving a methyl radical and a Ni(II)-SCoM species currently appears to be the most acceptable one for MCR. In the present paper, using hybrid density functional theory and an active-site model based on the X-ray crystal structure, two other mechanisms were studied and finally also ruled out. One of them, involving proton binding on the CH3-SCoM substrate, which should facilitate methyl-Ni(III)F-430 formation, is demonstrated to be quite unfavorable since the substrate has a much smaller proton affinity than the F-430 cofactor. Another one (oxidative addition mechanism) is also shown to be unfavorable for the MCR reaction, due to the large endothermicity for the formation of the ternary intermediate with side-on C-S (for CH3-SCoM) or C-H (for methane) coordination to Ni.

  • 236. Chen, Shi-Lu
    et al.
    Liao, Rong-Zhen
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Phosphate Monoester Hydrolysis by Trinuclear Alkaline Phosphatase; DFT Study of Transition States and Reaction Mechanism2014Ingår i: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 15, nr 11, s. 2321-2330Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Alkaline phosphatase (AP) is a trinuclear metalloenzyme that catalyzes the hydrolysis of a broad range of phosphate monoesters to form inorganic phosphate and alcohol (or phenol). In this paper, by using density functional theory with a model based on a crystal structure, the AP-catalyzed hydrolysis of phosphate monoesters is investigated by calculating two substrates, that is, methyl and p-nitrophenyl phosphates, which represent alkyl and aryl phosphates, respectively. The calculations confirm that the AP reaction employs a ping-pong mechanism involving two chemical displacement steps, that is, the displacement of the substrate leaving group by a Ser102 alkoxide and the hydrolysis of the phosphoseryl intermediate by a Zn2-bound hydroxide. Both displacement steps proceed via a concerted associative pathway no matter which substrate is used. Other mechanistic aspects are also studied. Comparison of our calculations with linear free energy relationships experiments shows good agreement.

  • 237. Chojnacka, Kinga
    et al.
    Santoro, Stefano
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Awartani, Radi
    Richards, Nigel G. J.
    Himo, Fahmi
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Aponick, Aaron
    Synthetic studies on the solanacol ABC ring system by cation-initiated cascade cyclization: implications for strigolactone biosynthesis2011Ingår i: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 9, nr 15, s. 5350-5353Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report a new method for constructing the ABC ringsystem of strigolactones, in a single step from a simple linearprecursor by acid-catalyzed double cyclization. The reactionproceeds with a high degree of stereochemical control, whichcan be qualitatively rationalized usingDFT calculations. Ourconcise synthetic approach offers a new model for thinkingabout the (as yet) unknown chemistry that is employed in thebiosynthetic pathways leading to this class of plant hormones.

  • 238. Chow, Winnie W. Y.
    et al.
    Herwik, Stanislav
    Kisban, Sebastian
    Ruther, Patrick
    Neves, Herc
    Oscarsson, Sven
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Gothelid, Emmanuelle
    Influence of bio-coatings on the recording performance of neural electrodes2014Ingår i: Biomedizinische Technik (Berlin. Zeitschrift), ISSN 1862-278X, E-ISSN 0013-5585, Vol. 59, nr 4, s. 315-322Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Neural probes are complex devices consisting of metallic (often Pt based) electrodes, spread over an insolating/dielectric backbone. Their functionality is often limited in time because of the formation of scaring tissues around the implantation tracks. Functionalization of the probes surface can be used to limit the glial scar reaction. This is however challenging, as this treatment has to be equally efficient on all probe surfaces (metallic as well as dielectric) and should not influence the electrodes performances. This paper presents a novel technique to functionalize recording neural probes with hyaluronic acid (HyA), a major component of the extracellular matrix (ECM). HyA and the probe surface are both modified to make the reaction feasible: HyA is chemically functionalized with SS-pyridine groups while the probe surfaces are silanized. The thiol groups thus introduced on the probe surface can then react with the HyA SS-pyridine group, resulting in a covalent bonding of the latter on the former. The electrodes are protected by introducing a pretreatment step, namely an additional hyaluronic acid layer on the platinum electrode, prior to the silanization process, which was found to be effective in reducing electrode impedance under optimized conditions.

  • 239. Chow, Winnie W. Y.
    et al.
    Herwik, Stanislav
    Ruther, Patrick
    Gothelid, Emmanuelle
    Oscarsson, Sven
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bio-polymer coatings on neural probe surfaces: Influence of the initial sample composition2012Ingår i: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 258, nr 20, s. 7864-7871Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents the results of the study of hyaluronic acid (HyA) coating on two structural materials, silicon oxide (dielectric) surface and platinum (Pt) surface used for fabrication of probes developed for neurological investigations in the framework of the EU-project NeuroProbes. The silicon-based neural probes consist of multiple Pt electrodes on the probe shafts for neural recording applications. HyA coatings were proposed to apply on the probe surfaces to enhance the biocompatibility [1]. This study aims at understanding the influence of the initial composition of the probe surface on the structure and morphology of HyA coating. HyA was chemically functionalized by SS-pyridin using (N-Succinimidyl 3-[2-pyridyldithio]-propionate) (SPDP) and was immobilized on the surfaces via a covalent bond. The dielectric and Pt surfaces were derivatized by use of (3-mercaptopropyl) methyldimethoxysilane (MPMDMS). The silanol groups in MPMDMS bind to the dielectric surface, leaving the thiol groups at the uppermost surface and the thiol groups then bind covalently to the functionalized HyA. On the Pt surface, it is the thiol group which binds on the Pt surface. The coated surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). A well-defined HyA layer was observed on both dielectric and Pt surfaces. The coating of two molecular weights (340 kDa and 1.3 MDa) of HyA was examined. The influence of the silanized layer on the HyA coating was also investigated.

  • 240. Chowdhury, Sugata
    et al.
    Himo, Fahmi
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Russo, Nino
    Sicilia, Emilia
    Mechanistic investigation of the hydrogenation of O2 by a transfer hydrogenation catalyst2010Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 132, nr 12, s. 4178-4190Artikel i tidskrift (Refereegranskat)
  • 241. Closson, Adam
    et al.
    Johansson, Mikael
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bäckvall, Jan-E.
    Ionic liquid-immobilized catalytic system for biomimetic dihydroxylation of olefins2004Ingår i: Chemical Communication, ISSN 0366-5607, nr 13, s. 1494-1495Artikel i tidskrift (Refereegranskat)
  • 242.
    Colas, Kilian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    New C-C coupling Reactions Enabled by Main-group Organometallics2018Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The carbon-carbon bond has always been at the very core of chemical research. Strategies for the creation of C−C bonds are one of the keys to the construction game that organic chemists play with the building blocks provided by Nature, with the ultimate goal of producing useful molecular structures that will serve society as medicines, materials, imaging tools, catalysts, and ligands (to mention but a few). While very different in their structure, all of these molecules are often prepared by the same methods. However, efficiency could be improved with tailored chemical strategies that would serve an individual purpose. Ideally, these chemical manipulations should be efficient, selective, environmentally friendly and economic, in order to truly fulfill their final objective.

    However, despite the ever-expanding rule-book of chemical reactions, target molecules of increasing complexity often face chemists with daunting challenges, whose success rely on multi-step synthetic sequences. There is therefore a permanent need for new, specific methods and strategies that are capable of seamlessly creating C−C bonds, evading the synthesis of difficult or expensive substrates. In this regard, common organometallic reagents display a unique behavior as carbon precursors, in particular as powerful nucleophiles. Reagents based on main-group elements such as lithium or magnesium have therefore played a central role in organic synthesis ever since their discovery. The challenge often lies in controlling their high reactivity, as well as their basic character. Tuning and taming these properties provides chemists with a wide range of unique strategies for the selective synthesis of countless molecular targets.

    In the first part of this thesis, a scalable and stereoselective [3+3] homocoupling of imines in which two C−C bonds are formed in a single step is reported. This reaction relies on an unusual combination of visible-light irradiation and aluminum organometallics. This photochemical process enables the circumvention of the native [3+2] reactivity of these readily available starting materials, thus enabling rapid access to densely functionalized piperazines. Thanks to the congested environment they provide, these heterocyclic scaffolds can be used as ligands to prevent catalyst deactivation through oligomerization.

    The next chapter presents a novel Pummerer-type redox-neutral coupling of sulfoxides and Grignard reagents. This reaction is enabled by a unique turbo-magnesium amide base, and allows the use of a wide range of carbon nucleophiles in intermolecular Pummerer C−C coupling for the streamlined preparation of thioethers. Given the central character of sulfur in organic chemistry, these compounds can then be converted to a variety of unrelated functional groups for the streamlined preparation of diverse building blocks.

    In the final two chapters, the development of a method for the direct conversion of carboxylic acids to ketones with Grignard reagents is described. Using the above-mentioned combination of organometallics, a wide variety of carboxylic acids substrates and Grignard reagents can be coupled in a convenient, scalable and highly selective method that suppresses the need for activation and offers a straightforward approach to ketones from readily available starting materials.

  • 243.
    Colas, Kilian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Martín-Montero, Raúl
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Mendoza, Abraham
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Intermolecular Pummerer Coupling with Carbon Nucleophiles in Non-Electrophilic Media2017Ingår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 56, nr 50, s. 16042-16046Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new Pummerer-type C-C coupling protocol is introduced based on turbo-organomagnesium amides, which unlike traditional Pummerer reactions, does not require strong electrophilic activators, engages a broad range of C(sp(3))-, C(sp(2))-, and C(sp)-nucleophiles, and seamlessly integrates with C-H and C-X magnesiation. Given the central character of sulfur compounds in organic chemistry, this protocol allows access to unrelated carbonyls, olefins, organometallics, halides, and boronic esters through a single strategy.

  • 244.
    Colas, Kilian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Mendoza, Abraham
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Iterative Synthesis of Pluripotent Thioethers through Controlled Redox Fluctuation of Sulfur2018Ingår i: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry, ISSN 0936-5214, E-ISSN 1437-2096, Vol. 29, nr 10, s. 1329-1333Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Target- and diversity-oriented syntheses are based on diverse building blocks, whose preparation requires discrete design and constructive alignment of different chemistries. To enable future automation of the synthesis of small molecules, we have devised a unified strategy that serves the divergent synthesis of unrelated scaffolds such as carbonyls, olefins, organometallics, halides, and boronic esters. It is based on iterations of a nonelectrophilic Pummerer-type C-C coupling enabled by turbo -organomagnesium amides that we have recently reported. The pluripotency of sulfur allows the central building blocks to be obtained by regulating C-C bond formation through control of its redox state.

  • 245.
    Colas, Kilian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Vieira Dias dos Santos, Ana Catarina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Mendoza, Abraham
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    One-pot Synthesis of Ketones from Aliphatic Carboxylic Acids Using Grignard Reagents and an in situ generated turbo-Hauser BaseManuskript (preprint) (Övrigt vetenskapligt)
  • 246.
    Colas, Kilian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Vieira Dias dos Santos, Ana Catarina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Mendoza, Abraham
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Synthesis of Ketones from Carboxylic Acids Using Grignard Reagents and turbo-Hauser BasesManuskript (preprint) (Övrigt vetenskapligt)
  • 247. Coll, Mercedes
    et al.
    Ahlford, Katrin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Pamies, Oscar
    Adolfsson, Hans
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Dieguez, Montserrat
    Modular Furanoside Pseudodipeptides and Thioamides, Readily Available Ligand Libraries for Metal-Catalyzed Transfer Hydrogenation Reactions: Scope and Limitations2012Ingår i: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 354, nr 2-3, s. 415-427Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two new highly modular carbohydrate-based, pseudodipeptide and thioamide ligand libraries have been synthesized for the rhodium- and ruthenium-catalyzed asymmetric transfer hydrogenation (ATH) of prochiral ketones. These series of ligands can be prepared efficiently from easily accessible D-xylose and D-glucose. The ligand libraries contain two main ligand structures (pseudodipeptide and thioamide) that have been designed by making systematic modifications to one of the most successful ligand families developed for the ATH. As well as studying the effect of these two ligand structures on the catalytic performance, we also evaluated the effect of modifying several of the ligand parameters. We found that the effectiveness of the ligands at transferring the chiral information in the product can be tuned by correctly choosing the ligand components (ligand structure and ligand parameters). Excellent enantioselectivities (ees up to 99%) were therefore obtained in both enantiomers of the alcohol products using a wide range of substrates.

  • 248. Coll, Mercedes
    et al.
    Pamies, Oscar
    Adolfsson, Hans
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Dieguez, Montserrat
    Second-Generation Amino Acid Furanoside Based Ligands from D-Glucose for the Asymmetric Transfer Hydrogenation of Ketones2013Ingår i: ChemCatChem, ISSN 1867-3880, E-ISSN 1867-3899, Vol. 5, nr 12, s. 3821-3828Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel series of modular amino acid thioamide ligands functionalized with carbohydrates were introduced and employed in the rhodium-catalyzed asymmetric transfer hydrogenation (ATH) of aryl alkyl ketones, including the less-studied heteroaromatic ketones. The ligands are based on amino acid hydroxyamides (pseudodipeptides), which are the most successful ligands previously used in asymmetric hydrogen transfer reactions. High enantioselectivities [up to 99% enantiomeric excess (ee)] were achieved in the ATH of a wide range of aryl alkyl ketones by using catalysts generated insitu from [RhCl2Cp*](2) (Cp*=C5Me5) and thioamide ligands comprising a 3-benzyl glucofuranoside backbone and a bulky isopropyl group in the -amino acid moiety. Interestingly, both enantiomers of the alcohol products can readily be obtained with high enantioselectivity by simply changing the absolute configuration of the -amino acid. The good performance can be extended to a very challenging class of industrially interesting heteroaromatic ketones (up to 99%ee).

  • 249. Coll, Mercedes
    et al.
    Pàmies, Oscar
    Adolfsson, Hans
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Diéguez, Montserrat
    Carbohydrate-based pseudo-dipeptides: new ligands for the highly enantioselective Ru-catalyzed transfer hydrogenation reaction2011Ingår i: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 47, nr 44, s. 12188-12190Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ruthenium-complexes of novel carbohydrate based pseudo-dipeptide ligands effectively and selectively catalyze the reduction of a broad range of aryl–alkyl ketones under ATH conditions. Excellent enantioselectivities (>99% ee) are obtained using aminosugars as the sole source of chirality.

  • 250.
    Cordova, Armando
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Lin, Shuangzheng
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Tseggai, Abrehet
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Concise catalytic asymmetric total synthesis of biologically active tropane alkaloids2012Ingår i: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 354, nr 7, s. 1363-1372Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A general strategy for the total asymmetric synthesis of valuable tropane alkaloids by catalytic stereoselective transformations is disclosed. The power of this approach is exemplified by the concise catalytic enantioselective total syntheses of (+)-methylecgonine, (-)-cocaine and (+)-cocaine as well as the first catalytic asymmetric total syntheses of a cocaine C-1 derivative and (+)-ferruginine starting from 5-oxo-protected-a,beta-unsaturated enals using only two and three column chromatographic purification steps, respectively.

2345678 201 - 250 av 1639
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