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  • 1.
    Abdelhamid, Hani Nasser
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bermejo-Gómez, Antonio
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martín-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    A water-stable lanthanide metal-organic framework for fluorimetric detection of ferric ions and tryptophan2017In: Microchimica Acta, ISSN 0026-3672, E-ISSN 1436-5073, Vol. 184, no 9, p. 3363-3371Article in journal (Refereed)
    Abstract [en]

    The preparation of a highly water stable and porous lanthanide metal-organic framework (MOF) nanoparticles (denoted SUMOF-7II; SU refers to Stockholm University) is described. SUMOF-7II was synthesized starting from the tritopic linker of 2,4,6-tri-p-carboxyphenyl pyridine (H3L2) and La(III) as metal clusters. SUMOF-7II forms a stable dispersion and displays high fluorescence emission with small variation over the pH range of 6 to 12. Its fluorescence is selectively quenched by Fe(III) ions compared to other metal ions. The intensity of the fluorescene emission drops drops linearly in 16.6–167 μM Fe(III) concentration range, and Stern-Volmer plots are linear. The limit of detection (LOD) is 16.6 μM (at an S/N ratio of >3). This indicator probe can also be used for selective detection of tryptophan among several amino acids. Compared to the free linker H3L2, SUMOF-7II offers improved sensitivity and selectivity of the investigated species.

  • 2.
    Abdel-Magied, Ahmed F.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Arafa, Wael A. A.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Laine, Tanja M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Shatskiy, Andrey
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Substituent Effects in Molecular Ruthenium Water Oxidation Catalysts Based on Amide Ligands2017In: ChemCatChem, ISSN 1867-3880, E-ISSN 1867-3899, Vol. 9, no 9, p. 1583-1587Article in journal (Refereed)
    Abstract [en]

    The production of clean and sustainable energy is considered as one of the most urgent issues for our society. Mastering the oxidation of water to dioxygen is essential for the production of solar fuels. A study of the influence of the substituents on the catalytic activity of a series of mononuclear Ru complexes (2a-e) based on a tetradentate ligand framework is presented. At neutral pH, using [Ru(bpy)(3)](PF6)(3) (bpy=2,2'-bipyridine) as the terminal oxidant, a good correlation between the turnover frequency (TOF) and the Hammett sigma(meta) parameters was obtained. Additionally, a general pathway for the deactivation of Ru-based catalysts 2a-e during the catalytic oxidation of water through poisoning by carbon monoxide was demonstrated. These results highlight the importance of ligand design for fine-tuning the catalytic activity of water oxidation catalysts.

  • 3.
    Angles d'Ortoli, Thibault
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hamark, Christoffer
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Structure-Reactivity Relationships of Conformationally Armed Disaccharide Donors and Their Use in the Synthesis of a Hexasaccharide Related to the Capsular Polysaccharide from Streptococcus pneumoniae Type 372017In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 82, no 15, p. 8123-8140Article in journal (Refereed)
    Abstract [en]

    To advance the field of glycobiology, efficient synthesis methods of oligosaccharides and glycoconjugates are a requisite. In glycosylation reactions using superarmed donors, both selectivity and reactivity issues must be considered, and we herein investigate these aspects for differently protected beta-linked 2-O-glycosylated glucosyl donors carrying bulky tert-butyldimethylsilyl groups to different extents. The acceptors in reactions being secondary alcohols presents a challenging situation with respect to steric crowding. Conformational pyranose ring equilibria of the superarmed disaccharide donors with axial-rich substituents contained skew and boat conformations, and three-state models were generally assumed. With NIS/TfOH as the promotor, 2,6-di-tert-butyl-4-methylpyridine as the base, and a dichloromethane/toluene solvent mixture, ethyl 1-thio-beta-d-glucosyl disaccharide donors having 6-O-benzyl group(s) besides tert-butyldimethylsilyl groups were efficiently coupled at -40 degrees C to the hydroxyl group at position 3 of glucopyranosyl acceptors to form beta-(1 -> 2),beta-(1 -> 3)-linked trisaccharides, isolated in excellent 95% yield. The more axial-rich donors in skew and boat conformations are thus preorganized closer to the assumed transition state in these glycosylation reactions. The developed methodology was subsequently applied in the synthesis of a multibranched hexasaccharide related to the capsular polysaccharide from Streptococcus pneumoniae type 37, which consists of a beta-(1 -> 3)-linked backbone and a beta-(1 -> 2)-linked side chain of D-glucosyl residues in disaccharide repeating units.

  • 4. Arafa, Wael A. A.
    et al.
    Mohamed, Ashraf M.
    Abdel-Magied, Ahmed F.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    ULTRASOUND-MEDIATED THREE-COMPONENT REACTION ON-WATER PROTOCOL FOR THE SYNTHESIS OF NOVEL MONO- AND BIS-1,3-THIAZIN-4-ONE DERIVATIVES2017In: Heterocycles, ISSN 0385-5414, E-ISSN 1881-0942, Vol. 94, no 8, p. 1439-1455Article in journal (Refereed)
    Abstract [en]

    Green synthetic and catalyst-free strategy towards the synthesis of novel mono- and bis-1,3-thiazin-4-one scaffolds through a one pot, reaction of carbon disulfide, monoacetylenic esters and amines under ultrasonication has been reported. The merits of this protocol comprise no need for tedious workup steps and afforded the desired products in excellent yields make this synthetic protocol more efficient and worthy of further attentiveness. Moreover, the method exhibited excellent score in a number of green metrics.

  • 5. Arafa, Wael Abdelgayed Ahmed
    et al.
    Abdel-Magied, Ahmed Fawzy
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Nuclear Material Authority, Egypt.
    Utilization of ultrasonic irradiation as green and effective one-pot protocol to prepare a novel series of bis-2-amino-1,3,4-oxa(thia) diazoles and bis-tetrazoles2017In: ARKIVOC, ISSN 1551-7004, E-ISSN 1551-7012, p. 327-340Article in journal (Refereed)
    Abstract [en]

    In an effective and straightforward conversion, bis-semicarbazones and bis-thiosemicarbazones are transformed into a diversity of novel substituted bis-2-amino-1,3,4-oxadiazoles and bis-2-amino-1,3,4-thiadiazoles, respectively under ultrasonic irradiation. Bis-tetrazoles are obtained from the dialdehydes by sequential reaction with hydroxylamine hydrochloride, phosphorus pentoxide and sodium azide without isolation of the intermediates oximes and nitriles. All the reactions proceed cleanly and smoothly under mild conditions, with short reaction times and broad functional groups possibility. No side reactions were observed. [GRAPHICS]

  • 6. Bermejo Góme, Antonio
    et al.
    Cortés González, Miguel A.
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Karolinska Intitutet, Sweden.
    Lübcke, Marvin
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Karolinska Intitutet, Sweden.
    Johansson, Magnus J.
    Schou, Magnus
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Karolinska Intitutet, Sweden.
    Synthesis of trifluoromethyl moieties by late-stage copper (I) mediated nucleophilic fluorination2017In: Journal of fluorine chemistry, ISSN 0022-1139, E-ISSN 1873-3328, Vol. 194, p. 51-57Article in journal (Refereed)
    Abstract [en]

    The nucleophilic fluorination of bromodifluoromethyl derivatives mediated by the complex (PPh3)(3)CuF is described. Under the reaction conditions, different trifluoroacetates, trifluorolcetones, trifluoroarenes and trifluoroacetamides were obtained in good yields.

  • 7.
    Blasco, Pilar
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Patel, Dhilon S.
    Engström, Olof
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Im, Wonpil
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Conformational Dynamics of the Lipopolysaccharide from Escherichia coli O91 Revealed by Nuclear Magnetic Resonance Spectroscopy and Molecular Simulations2017In: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 56, no 29, p. 3826-3839Article in journal (Refereed)
    Abstract [en]

    The outer leaflet of the outer membrane in Gram-negative bacteria contains lipopolysaccharides (LPS) as a major component, and the outer membrane provides a physical barrier and protection against hostile environments. The enterohemorrhagic Escherichia coli of serogroup O91 has an O-antigen polysaccharide (PS) with five sugar residues in the repeating unit (RU), and the herein studied O-antigen PS contains similar to 10 RUs. H-1-C-13 HSQC-NOESY experiments on a 1-C-13-labeled PS were employed to deduce H-1-H-1 cross-relaxation rates and transglycosidic (3)J(CH) related to the psi torsional angles were obtained by H-1-H-1 NOESY experiments. Dynamical parameters were calculated from the molecular dynamics (MD) simulations of the PS in solution and compared to those from C-13 nuclear magnetic resonance (NMR) relaxation studies. Importantly, the MD simulations can reproduce the dynamical behavior of internal correlation times along the PS chain. Two-dimensional free energy surfaces of glycosidic torsion angles delineate the conformational space available to the O-antigen. Although similar with respect to populated states in solution, the O-antigen in LPS bilayers has more extended chains as a result of spatial limitations due to close packing. Calcium ions are highly abundant in the phosphate-containing core region mediating LPS LPS association that is crucial for maintaining bilayer integrity, and the negatively charged O-antigen promotes a high concentration of counterbalancing potassium ions. The ensemble of structures present for the PS in solution is captured by the NMR experiments, and the similarities between the O-antigen on its own and as a constituent of the full LPS in a bilayer environment make it possible to realistically describe the LPS conformation and dynamics from the MD simulations.

  • 8.
    Blomberg, Margareta R. A.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Can Reduction of NO to N2O in Cytochrome c Dependent Nitric Oxide Reductase Proceed through a Trans-Mechanism?2017In: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 56, no 1, p. 120-131Article in journal (Refereed)
    Abstract [en]

    As part of microbial denitrification, NO is reduced to N2O in the membrane bound enzyme nitric oxide reductase, NOR The N N coupling occurs in the diiron binuclear active site, BNC, and different mechanisms for this reaction step have been suggested. Computational studies have supported a so-called cis:b(3)-mechanism, in which the hyponitrite product of the reductive N N bond formation coordinates with one nitrogen to the heme iron and with both oxygens to the non-heme iron in the BNC. In contrast, experimental results have been interpreted to support a so-called trans-mechanism, in which the hyponitrite intermediate coordinates with one nitrogen atom to each of the two iron ions. Hybrid density functional theory is used here to perform an extensive search for possible intermediates of the NO reduction in the cNOR enzyme. It is found that hyponitrite structures coordinating with their negatively charged oxygens to the positively charged iron ions are the most stable ones. The hyponitrite intermediate involved in the suggested trans-mechanism, which only coordinates with the nitrogens to the iron ions, is found to be prohibitively high in energy, leading to a too slow reaction, which should rule out this mechanism. Furthermore, intermediates binding one NO molecule to each iron ion in the BNC, which have been suggested to initiate the trans-mechanism, are found to be too high in energy to be observable, indicating that the experimentally observed electron paramagnetic resonance signals, taken to support such an iron-nitrosyl dimer intermediate, should be reinterpreted.

  • 9.
    Blomberg, Margareta R. A.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ädelroth, Pia
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    The mechanism for oxygen reduction in cytochrome c dependent nitric oxide reductase (cNOR) as obtained from a combination of theoretical and experimental results2017In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1858, no 11, p. 884-894Article in journal (Refereed)
    Abstract [en]

    Bacterial NO-reductases (NOR) belong to the heme-copper oxidase (HCuO) superfamily, in which most members are O-2-reducing, proton-pumping enzymes. This study is one in a series aiming to elucidate the reaction mechanisms of the HCuOs, including the mechanisms for cellular energy conservation. One approach towards this goal is to compare the mechanisms for the different types of HCuOs, cytochrome c oxidase (CcO) and NOR, reducing the two substrates O-2 and NO. Specifically in this study, we describe the mechanism for oxygen reduction in cytochrome c dependent NOR (cNOR). Hybrid density functional calculations were performed on large cluster models of the cNOR binuclear active site. Our results are used, together with published experimental information, to construct a free energy profile for the entire catalytic cycle. Although the overall reaction is quite exergonic, we show that during the reduction of molecular oxygen in cNOR, two of the reduction steps are endergonic with high barriers for proton uptake, which is in contrast to oxygen reduction in CcO, where all reduction steps are exergonic. This difference between the two enzymes is suggested to be important for their differing capabilities for energy conservation. An additional result from this study is that at least three of the four reduction steps are initiated by proton transfer to the active site, which is in contrast to CcO, where electrons always arrive before the protons to the active site. The roles of the non-heme metal ion and the redox-active tyrosine in the active site are also discussed.

  • 10.
    Bruneau, Alexandre
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Gustafson, Karl P. J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Yuan, Ning
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Swedish University of Agricultural Sciences, Sweden.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Persson, Ingmar
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Synthesis of Benzofurans and Indoles from Terminal Alkynes and Iodoaromatics Catalyzed by Recyclable Palladium Nanoparticles Immobilized on Siliceous Mesocellular Foam2017In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, no 52, p. 12886-12891Article in journal (Refereed)
    Abstract [en]

    Herein, we report on the utilization of a heterogeneous catalyst, consisting of Pd nanoparticles supported on a siliceous mesocellular foam (Pd-0-AmP-MCF), for the synthesis of heterocycles. Reaction of o-iodophenols and protected o-iodoanilines with acetylenes in the presence of a Pd nanocatalyst produced 2-substituted benzofurans and indoles, respectively. In general, the catalytic protocol afforded the desired products in good to excellent yields under mild reaction conditions without the addition of ligands. Moreover, the structure of the reported Pd nanocatalyst was further elucidated with extended X-ray absorption fine-structure spectroscopy, and it was proven that the catalyst could be recycled multiple times without significant loss of activity.

  • 11. Casillo, Angela
    et al.
    Ståhle, Jonas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Parrilli, Ermenegilda
    Sannino, Filomena
    Mitchell, Daniel E.
    Pieretti, Giuseppina
    Gibson, Matthew I.
    Marino, Gennaro
    Lanzetta, Rosa
    Parrilli, Michelangelo
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Tutino, Maria L.
    Corsaro, Maria M.
    Structural characterization of an all-aminosugar-containing capsular polysaccharide from Colwellia psychrerythraea 34H2017In: Antonie van Leeuwenhoek. International Journal of General and Molecular Microbiology, ISSN 0003-6072, E-ISSN 1572-9699, Vol. 110, no 11, p. 1377-1387Article in journal (Refereed)
    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.

  • 12.
    Colas, Kilian
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martín-Montero, Raúl
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mendoza, Abraham
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Intermolecular Pummerer Coupling with Carbon Nucleophiles in Non-Electrophilic Media2017In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 56, no 50, p. 16042-16046Article in journal (Refereed)
    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.

  • 13.
    Daver, Henrik
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Harvey, Jeremy N.
    Rebek, Jr., Julius
    Himo, Fahmi
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Quantum Chemical Modeling of Cycloaddition Reaction in a Self-Assembled Capsule2017In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 139, no 43, p. 15494-15503Article in journal (Refereed)
    Abstract [en]

    Dispersion-corrected density functional theory is used to study the cycloaddition reaction between phenyl acetylene and phenyl azide inside a synthetic, self-assembled capsule. The capsule is first characterized computationally and a previously unrecognized structure is identified as being the most stable. Next, an examination of the free energies of host-guest complexes is conducted, considering all possible reagent, solvent and solvent impurity combinations as guests. The experimentally observed relative stabilities of host-guest complexes are quite well reproduced, when the experimental concentrations are taken into account. Experimentally, the presence of the host capsule has been shown to accelerate the cycloaddition reaction and to yield exclusively the 1,4-regioisomer product. Both these observations are reproduced by the calculations. A detailed energy decomposition analysis shows that reduction of the entropic cost of bringing together the reactants along with a geometric destabilization of the reactant supercomplex are the major contributors to the rate acceleration compared to the background reaction. Finally, a sensitivity analysis is conducted to assess the stability of the results with respect to the choice of methodology.

  • 14.
    Engström, Olof
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mobarak, Hani
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ståhle, Jonas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Conformational Dynamics and Exchange Kinetics of N-Formyl and N-Acetyl Groups Substituting 3-Amino-3,6-dideoxy-alpha-D-galactopyranose, a Sugar Found in Bacterial O-Antigen Polysaccharides2017In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 121, no 41, p. 9487-9497Article in journal (Refereed)
    Abstract [en]

    Three dimensional shape and conformation of. carbohydrates are important factors in molecular recognition events and the N-acetyl group of a monosaccharide residue can function as a conformational gatekeeper whereby it influences the overall shape of the oligosaccharide. NMR spectroscopy and quantum mechanics (QM) calculations are used herein to investigate both the conformational preferences and the dynamic behavior of N-acetyl and N-formyl substituents of 3-amino-3,6-dideoxy-alpha-D-galactopyranose, a sugar and substitution pattern found in bacterial O-antigen polysaccharides. QM calculations suggest that the amide oxygen can be involved in hydrogen bonding with the axial OH4 group primarily but also with the equatorial OH2 group. However, an NMR J coupling analysis indicates that the 01 torsion angle, adjacent to the sugar ring, prefers an ap conformation where conformations <180 degrees also are accessible, but does not allow for intramolecular hydrogen bonding. In the formyl-substituted compound (4)J(HH) coupling constants to the exo-cyclic group were detected and analyzed. A van't Hoff analysis revealed that the trans conformation at the amide bond is favored by Delta G degrees approximate to - 0.8 kcal.mol(-1) in the formyl-containing compound and with Delta G degrees approximate to -2.5 kcal.mol(-1) when the N-acetyl group is the substituent. In both cases the enthalpic term dominates to the free energy, irrespective of water or DMSO as solvent, with only a small contribution from the entropic term. The cis-trans isomerization of the theta(2) torsion angle, centered at the amide bond, was also investigated by employing H-1 NMR line shape analysis and C-13 NMR saturation transfer experiments. The extracted transition rate constants were utilized to calculate transition energy barriers that were found to be about 20 kcal.mol(-1) in both DMSO-d(6) and D2O. Enthalpy had a higher contribution to the energy barriers in DMSO-d(6) compared to in D2O, where entropy compensated for the loss of enthalpy.

  • 15.
    Fawzy Abdel-Magied, Ahmed
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Nuclear Materials Authority, Egypt.
    Solid phase extraction of uranium from phosphoric acid: kinetic and thermodynamic study2017In: Radiochimica Acta, ISSN 0033-8230, E-ISSN 2193-3405, Vol. 105, no 10, p. 813-820Article in journal (Refereed)
    Abstract [en]

    There is a high interest to develop suitable solid phase extractants for uranium separation from aqueous solutions in order to reduce cost and enhance the efficiency. This paper describes solid phase extraction of uranium(VI) from aqueous phosphoric acid solution using MCM-41 based D2HEPA-TOPO organophosphorous extractants. The mixture of D2HEPA (di-2-ethyl-hexylphosphoric acid) and TOPO (tri-n-octylphosphine oxide) was impregnated into the pores of MCM-41 and the synthesized sorbent was fully characterized. The influences of different factors such as synergistic mixture ratio, phosphoric acid concentration, mixing time and temperature were investigated. The results showed that 90% of uranium(VI) extraction can be achieved within 5 min, using D2HEPATOPO@MCM-41 (mass ratio 2: 1 w/w) from 1 M phosphoric acid containing 64 ppm of uranium at room temperature. High adsorption capacity of uranium(VI) have been achieved at the mentioned conditions. The rate constant for the chemical adsorption of uranium(VI) was 0.988 g mg. 1 min. 1 calculated by the pseudo-second order rate equation. The obtained thermodynamics parameters showed that uranium(VI) adsorption from H-3 PO4 is an exothermic and spontaneous process.

  • 16. François, Camille
    et al.
    Pourchet, Sylvie
    Boni, Gilles
    Rautiainen, Sari
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Samec, Joseph
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Fournier, Lucie
    Robert, Carine
    Thomas, Christophe M.
    Fontaine, Stephane
    Gaillard, Yves
    Placet, Vincent
    Plasseraud, Laurent
    Design and synthesis of biobased epoxy thermosets from biorenewable resources2017In: Comptes rendus. Chimie, ISSN 1631-0748, E-ISSN 1878-1543, Vol. 20, no 11-12, p. 1006-1016Article in journal (Refereed)
    Abstract [en]

    Biobased diepoxy synthons derived from isoeugenol, eugenol or resorcinol (DGE-isoEu, DGE-Eu and DGER, respectively) have been used as epoxy monomers in replacement of the diglycidyl ether of bisphenol A (DGEBA). Their curing with six different biobased anhydride hardeners leads to fully biobased epoxy thermosets. These materials exhibit interesting thermal and mechanical properties comparable to those obtained with conventional petrosourced DGEBA-based epoxy resins cured in similar conditions. In particular, a high T-g in the range of 90-130 degrees C and instantaneous moduli higher than 4.3 GPa have been recorded. These good performances are very encouraging, making these new fully biobased epoxy thermosets compatible with the usual structural application of epoxy materials.

  • 17.
    González Miera, Greco
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nonclassical cyclodehydration of diols assisted by metal-ligand cooperation2017Article in journal (Refereed)
  • 18.
    González Miera, Greco
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bermejo Gómez, Antonio
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Chupas, Peter J.
    Martín-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Chapman, Karena W.
    Platero-Prats, Ana E.
    Topological Transformation of a Metal–Organic Framework Triggered by Ligand Exchange2017In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 56, no 8, p. 4576-4583Article in journal (Refereed)
    Abstract [en]

    Here we describe the topological transformation of the pores of a new framework in the bio-MOF-100 family (dia-c) into the known isomer (lcs) by doubling the pore volume, which occurs during postsynthesis modifications. During this transformation, reassembling of the metal–organic framework (MOF) building blocks into a completely different framework occurs, involving breaking/forming of metal–ligand bonds. MOF crystallinity and local structure are retained, as determined by powder X-ray diffraction (PXRD) and pair distribution function (PDF) analyses, respectively. We exploited the inherent dynamism of bio-MOF-100 by coupling chemical decorations of the framework using solvent-assisted ligand exchange to the topological change. Following this method and starting from the pristine dense dia-c phase, open lcs-bio-MOF-100 was prepared and functionalized in situ with an iridium complex (IrL). Alternatively, the dia-c MOF could be modified with wide-ranging amounts of IrL up to ca. 50 mol %, as determined by solution 1H NMR spectroscopy, by tuning the concentration of the solutions used and with no evidence for isomer transformation. The single-site nature of the iridium complexes within the MOFs was assessed by X-ray absorption spectroscopy (XAS) and PDF analyses. Ligand exchanges occurred quantitatively at room temperature, with no need of excess of the iridium metallolinker.

  • 19.
    González Miera, Greco
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martínez-Castro, Elisa
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martín-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Acceptorless Alcohol Dehydrogenation: OH vs NH Effect in Bifunctional NHC–Ir(III) Complexes2017In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041Article in journal (Refereed)
    Abstract [en]

    Bifunctional complexes bearing N-heterocyclic carbene (NHC) ligands functionalized with hydroxy or amine groups were synthesized to measure the beneficial effect of different modes of metal–ligand cooperation in the acceptorless dehydrogenation of alcohols. In comparison to complexes with an amine moiety, hydroxy-functionalized iridium catalysts showed superior activity. In contrast to alcohols, 1,4-diols underwent cyclization to give the corresponding tetrahydrofurans without involving dehydrogenation processes. Mechanistic investigations to rationalize the “OH effect” in these types of complexes have been undertaken.

  • 20. Goulart, Paula N.
    et al.
    da Silva, Clarissa O.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    The importance of orientation of exocyclic groups in a naphthoxyloside: A specific rotation calculation study2017In: Journal of Physical Organic Chemistry, ISSN 0894-3230, E-ISSN 1099-1395, Vol. 30, no 12, article id e3708Article in journal (Refereed)
    Abstract [en]

    2-Naphthyl -d-xylopyranoside (XylNap) inhibits -1,4-galactosyltransferase 7 (4GalT7) and thereby growth of tumor cells both in vitro and in vivo. The binding pocket of 4GalT7 has a defined orientation of hydrogen bond acceptors and hydrophobic moiety. Knowing the orientation of the hydroxyl and naphthyl groups of this molecule would help in the development of more efficient inhibitors. In this work, we have tried, for the first time, to determine the exocyclic hydroxyl and aglycon groups orientation of XylNap, using ab initio descriptions, and calculation of the specific rotation values, in methanol solutions, using 2 different solvent descriptions: a dielectric continuum approach (polarizable continuum model [PCM]) and a microsolvated+continuum approach (MS+PCM). In the PCM approach, [](D)=-59 deg/(dm(g/cm(3))) whereas for the MS+PCM approach [](D)=-29 deg/(dm(g/cm(3))). The latter is in excellent agreement with the experimentally determined value in methanol solution, viz, [](D)=-30 deg/(dm(g/cm(3))). This agreement allows us to say that the hydroxyl groups have similar orientations in xylose and XylNap, and the naphthyl group has a very well-defined dihedral angle value in the most abundant conformations.

  • 21. Gupta, Arvind Kumar
    et al.
    Akkarasamiyo, Sunisa
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Orthaber, Andreas
    Rich Coordination Chemistry of pi-Acceptor Dibenzoarsole Ligands2017In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 56, no 8, p. 4504-4511Article in journal (Refereed)
    Abstract [en]

    A series of dibenzoarsole (also known as 9-arsafluorene) derivatives have been prepared, and their coordination chemistry has been investigated. The different ligand topology and the arsenic substituents govern the reactivity of the ligands. We report various crystal structures of palladium and platinum complexes derived from this family of ligands. The biphenyl backbone of the bridged bidentate ligands allows very flexible coordination. We have also studied the application of an allylic Pd complex in nucleophilic substitution reactions, revealing that the benzoarsole substituent is susceptible to metal insertion.

  • 22.
    Gustafson, Karl P. J.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Gudmundsson, Arnar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lewis, Kayla
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Chemoenzymatic Dynamic Kinetic Resolution of Secondary Alcohols Using an Air- and Moisture-Stable Iron Racemization Catalyst2017In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, no 5, p. 1048-1051Article in journal (Refereed)
    Abstract [en]

    Herein, we report on a metalloenzymatic dynamic kinetic resolution of sec-alcohols employing an iron-based racemization catalyst together with a lipase. The iron catalyst was evaluated in racemization and then used in dynamic kinetic resolution of a number of sec-alcohols to give enantiomerically pure products in good to high yields. The iron catalyst is air and moisture stable and is readily accessible.

  • 23.
    Gustafson, Karl P. J.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Shatskiy, Andrey
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Verho, Oscar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Schluschass, Bastian
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Water oxidation mediated by ruthenium oxide nanoparticles supported on siliceous mesocellular foam2017In: Catalysis Science & Technology, ISSN 2044-4753, E-ISSN 2044-4761, Vol. 7, no 1, p. 293-299Article in journal (Refereed)
    Abstract [en]

    Artificial photosynthesis is an attractive strategy for converting solar energy into fuel. In this context, development of catalysts for oxidation of water to molecular oxygen remains a critical bottleneck. Herein, we describe the preparation of a well-defined nanostructured RuO2 catalyst, which is able to carry out the oxidation of water both chemically and photochemically. The developed heterogeneous RuO2 nanocatalyst was found to be highly active, exceeding the performance of most known heterogeneous water oxidation catalysts when driven by chemical or photogenerated oxidants.

  • 24.
    Gustafsson, Robert
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Jemth, Ann-Sofie
    Gustafsson, Nina M. S.
    Färnegårdh, Katarina
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Stockholm University, Science for Life Laboratory (SciLifeLab).
    Loseva, Olga
    Wiita, Elisée
    Bonagas, Nadilly
    Dahllund, Leif
    Llona-Minguez, Sabin
    Häggblad, Maria
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Stockholm University, Science for Life Laboratory (SciLifeLab).
    Henriksson, Martin
    Andersson, Yasmin
    Homan, Evert
    Helleday, Thomas
    Stenmark, Pal
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Crystal Structure of the Emerging Cancer Target MTHFD2 in Complex with a Substrate-Based Inhibitor2017In: Cancer Research, ISSN 0008-5472, E-ISSN 1538-7445, Vol. 77, no 4, p. 937-948Article in journal (Refereed)
    Abstract [en]

    To sustain their proliferation, cancer cells become dependent on one-carbon metabolism to support purine and thymidylate synthesis. Indeed, one of the most highly upregulated enzymes during neoplastic transformation is MTHFD2, a mitochondrial methylenetetrahydrofolate dehydrogenase and cyclohydrolase involved in one-carbon metabolism. Because MTHFD2 is expressed normally only during embryonic development, it offers a disease-selective therapeutic target for eradicating cancer cells while sparing healthy cells. Here we report the synthesis and preclinical characterization of the first inhibitor of human MTHFD2. We also disclose the first crystal structure of MTHFD2 in complex with a substrate-based inhibitor and the enzyme cofactors NAD(+) and inorganic phosphate. Our work provides a rationale for continued development of a structural framework for the generation of potent and selective MTHFD2 inhibitors for cancer treatment.

  • 25.
    Görbe, Tamás
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Gustafson, Karl P. J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Verho, Oscar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kervefors, Gabriella
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zheng, Haoquan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Design of a Pd(0)-CalB CLEA Biohybrid Catalyst and Its Application in a One-Pot Cascade Reaction2017In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 7, no 3, p. 1601-1605Article in journal (Refereed)
    Abstract [en]

    Herein, a design of a biohybrid catalyst is described, consisting of Pd nanoparticles and a cross-linked network of aggregated lipase B enzyme of Candida antarctica (CalB CLEA) functioning as an active support for the Pd nanoparticles. Both entities of the hybrid catalyst showed good catalytic activity. The applicability was demonstrated in a one-pot reaction, where the Pd-catalyzed cycloisomerization of 4-pentynoic acid afforded a lactone that serves as an acyl donor in a subsequent selective enzymatic kinetic resolution of a set of sec-alcohols. The catalyst proved to be robust and could be recycled five times without a significant loss of activity.

  • 26.
    Hamark, Christoffer
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Berntsson, Ronnie P. -A.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Masuyer, Geoffrey
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Henriksson, Linda M.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Gustafsson, Robert
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Stenmark, Pål
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Glycans Confer Specificity to the Recognition of Ganglioside Receptors by Botulinum Neurotoxin A2017In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 139, no 1, p. 218-230Article in journal (Refereed)
    Abstract [en]

    The highly poisonous botulinum neurotoxins, produced by the bacterium Clostridium botulinum, act on their hosts by a high-affinity association to two receptors on neuronal cell surfaces as the first step of invasion. The glycan motifs of gangliosides serve as initial coreceptors for these protein complexes, whereby a membrane protein receptor is bound. Herein we set out to characterize the carbohydrate minimal binding epitope of the botulinum neurotoxin serotype A. By means of ligand-based NMR spectroscopy, X-ray crystallography, computer simulations, and isothermal titration calorimetry, a screening of ganglioside analogues together with a detailed characterization of various carbohydrate ligand complexes with the toxin were accomplished. We show that the representation of the glycan epitope to the protein affects the details of binding. Notably, both branches of the oligosaccharide GD la can associate to botulinum neurotoxin serotype A when expressed as individual trisaccharides. It is, however, the terminal branch of GD1a as well as this trisaccharide motif alone, corresponding to the sialyl-Thomsen-Friedenreich antigen, that represents the active ligand epitope, and these compounds bind to the neurotoxin with a high degree of predisposition but with low affinities. This finding does not correlate with the oligosaccharide moieties having a strong contribution to the total affinity, which was expected to be the case. We here propose that the glycan part of the ganglioside receptors mainly provides abundance and specificity, whereas the interaction with the membrane itself and protein receptor brings about the strong total binding of the toxin to the neuronal membrane.

  • 27.
    Henry, Jeffrey L.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Posevins, Daniels
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Yang, Bin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Qiu, Youai
    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 Pd-II-Catalyzed Oxidative Alkynylation of Enallenes2017In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, no 33, p. 7896-7899Article in journal (Refereed)
    Abstract [en]

    An olefin-assisted, palladium-catalyzed oxidative alkynylation of enallenes for regio- and stereoselective synthesis of substituted trienynes has been developed. The reaction shows a broad substrate scope and good tolerance for various functional groups on the allene moiety, including carboxylic acid esters, free hydroxyls, imides, and alkyl groups. Also, a wide range of terminal alkynes with electron-donating and electron-withdrawing aryls, heteroaryls, alkyls, trimethylsilyl, and free hydroxyl groups are tolerated.

  • 28.
    Heshmat, Mojgan
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Privalov, Timofei
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    A Prediction of Proton-Catalyzed Hydrogenation of Ketones in Lewis Basic Solvent through Facile Splitting of Hydrogen Molecules2017In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, no 5, p. 1036-1039Article in journal (Refereed)
    Abstract [en]

    A ketone's carbonyl carbon is electrophilic and harbors a part of the lowest unoccupied molecular orbital of the carbonyl group, resembling a Lewis acidic center; under the right circumstances it exhibits very useful chemical reactivity, although the natural electrophilicity of the ketone's carbonyl carbon is often not strong enough on its own to produce such reactivity. Quantum chemical calculations predict that a proton shared between a ketone and the Lewis basic solvent molecule (dioxane or THF) activates carbonyl carbon to the point of enabling a facile heterolytic splitting of H-2. Proton-catalyzed hydrogenation of a ketone in Lewis basic solvent is the result. The mechanism involves the interaction of H-2 with the enhanced Lewis acidity of a carbonyl carbon and the free Lewis basic solvent molecule polarizes H-2 and enables the hydride-type attack on carbonyl carbon, which is very strongly influenced by the proton shared between a ketone and solvent. The hydride-type attack on carbon is reminiscent of the splitting of H-2 by singlet carbenes except that, in this case, a Lewis base from the surrounding environment (solvent) is necessary for polarization of H-2 and acceptance of the proton resulting from the heterolytic splitting of H-2.

  • 29.
    Heshmat, Mojgan
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Privalov, Timofei
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Carbonyl Activation by Borane Lewis Acid Complexation: Transition States of H-2 Splitting at the Activated Carbonyl Carbon Atom in a Lewis Basic Solvent and the Proton-Transfer Dynamics of the Boroalkoxide Intermediate2017In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, no 38, p. 9098-9113Article in journal (Refereed)
    Abstract [en]

    By using transition-state (TS) calculations, we examined how Lewis acid (LA) complexation activates carbonyl compounds in the context of hydrogenation of carbonyl compounds by H-2 in Lewis basic (ethereal) solvents containing borane LAs of the type (C6F5)(3)B. According to our calculations, LA complexation does not activate a ketone sufficiently enough for the direct addition of H-2 to the O = C unsaturated bond; but, calculations indicate a possibly facile heterolytic cleavage of H-2 at the activated and thus sufficiently Lewis acidic carbonyl carbon atom with the assistance of the Lewis basic solvent (i.e., 1,4-dioxane or THF). For the solvent-assisted H-2 splitting at the carbonyl carbon atom of (C6F5)(3)B adducts with different ketones, a number of TSs are computed and the obtained results are related to insights from experiment. By using the Born-Oppenheimer molecular dynamics with the DFT for electronic structure calculations, the evolution of the (C6F5)(3)B-alkoxide ionic intermediate and the proton transfer to the alkoxide oxygen atom were investigated. The results indicate a plausible hydrogenation mechanism with a LA, that is, (C6F5)(3)B, as a catalyst, namely, 1) the step of H-2 cleavage that involves a Lewis basic solvent molecule plus the carbonyl carbon atom of thermodynamically stable and experimentally identifiable (C6F5)(3)B-ketone adducts in which (C6F5)(3)B is the Lewis acid promoter, 2) the transfer of the solvent-bound proton to the oxygen atom of the (C6F5)(3)B-alkoxide intermediate giving the (C6F5)(3)B-alcohol adduct, and 3) the S(N)2-style displacement of the alcohol by a ketone or a Lewis basic solvent molecule.

  • 30.
    Heshmat, Mojgan
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Privalov, Timofei
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Computational Elucidation of a Role That Bronsted Acidification of the Lewis Acid-Bound Water Might Play in the Hydrogenation of Carbonyl Compounds with H-2 in Lewis Basic Solvents2017In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, no 48, p. 11489-11493Article in journal (Refereed)
    Abstract [en]

    Bronsted acidification of water by Lewis acid (LA) complexation is one of the fundamental principles in chemistry. Using transition-state calculations (TS), herein we investigate the role that Bronsted acidification of the LA-bound water might play in the mechanism of the hydrogenation of carbonyl compounds in Lewis basic solvents under non-anhydrous conditions. The potential energy scans and TS calculations were carried out with a series of eight borane LAs as well as the commonly known strong LA AlCl3 in 1,4-dioxane or THF as Lewis basic solvents. Our molecular model consists of the dative LA-water adduct with hydrogen bonds to acetone and a solvent molecule plus one additional solvent molecule that participates is the TS structure describing the cleavage of H-2 at acetone's carbonyl carbon atom. In all the molecular models applied here, acetone (O=CMe2) is the archetypical carbonyl substrate. We demonstrate that Bronsted acidification of the LA-bound water can indeed lower the barrier height of the solvent-involving H-2-cleavage at the acetone's carbonyl carbon atom. This is significant because at present it is believed that the mechanism of the herein considered reaction is described by the same mechanism regardless of whether the reaction conditions are strictly anhydrous or non-anhydrous. Our results offer an alternative to this belief that warrants consideration and further study.

  • 31.
    Heshmat, Mojgan
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Privalov, Timofei
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Theory-Based Extension of the Catalyst Scope in the Base-Catalyzed Hydrogenation of Ketones: RCOOH-Catalyzed Hydrogenation of Carbonyl Compounds with H-2 Involving a Proton Shuttle2017In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, no 72, p. 18193-18202Article in journal (Refereed)
    Abstract [en]

    As an extension of the reaction mechanism describing the base-catalyzed hydrogenation of ketones according to Berkessel et al., we use a standard methodology for transition-state (TS) calculations in order to check the possibility of heterolytic cleavage of H-2 at the ketone's carbonyl carbon atom, yielding one-step hydrogenation path with involvement of carboxylic acid as a catalyst. As an extension of the catalyst scope in the base-catalyzed hydrogenation of ketones, our mechanism involves a molecule with a labile proton and a Lewis basic oxygen atom as a catalyst-for example, R-C(= O) OH carboxylic acids-so that the heterolytic cleavage of H-2 could take place between the Lewis basic oxygen atom of a carboxylic acid and the electrophilic (Lewis acidic) carbonyl carbon of a ketone/aldehyde. According to our TS calculations, protonation of a ketone/aldehyde by a proton shuttle (hydrogen bond) facilitates the hydride-type attack on the ketone's carbonyl carbon atom in the process of the heterolytic cleavage of H-2. Ketones with electron-rich and electron-withdrawing substituents in combination with a few carboxylic and amino acids-in total, 41 substrate-catalyst couples-have been computationally evaluated in this article and the calculated reaction barriers are encouragingly moderate for many of the considered substrate-catalyst couples.

  • 32. Huang, Genping
    et al.
    Diner, Colin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Himo, Fahmi
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mechanism and Stereoselectivity of the BINOL-Catalyzed Allylboration of Skatoles2017In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 19, no 21, p. 5904-5907Article in journal (Refereed)
    Abstract [en]

    Density functional theory calculations have been performed to investigate the binaphthol-catalyzed allylboration of skatoles. The high stereoselectivity observed for the reaction is reproduced well by the calculations and was found to be mainly a result of steric repulsions in the corresponding Zimmerman-Traxler transition states. The role of the additive MeOH in enhancing the stereoselectivity was also investigated and is suggested to promote the formation of less reactive allylboronic ester intermediates, thereby suppressing the formation of allylboroxine species, which undergo the facile racemic background reaction.

  • 33.
    Ilchenko, Nadia O.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hedberg, Martin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Fluorinative ring-opening of cyclopropanes by hypervalent iodine reagents. An efficient method for 1,3-oxyfluorination and 1,3-difluorination2017In: Chemical Sience, ISSN 2041-6520, Vol. 8, no 2, p. 1056-1061Article in journal (Refereed)
    Abstract [en]

    A new method is presented for 1,3-difluorination and 1,3-oxyfluorination reactions. The process is based on iodonium mediated opening of 1,1-disubstituted cyclopropanes. The reaction proceeds with high chemo- and regioselectivity under mild reaction conditions typically at room temperature in a couple of hours. The reaction probably occurs via electrophilic ring-opening of cyclopropanes.

  • 34.
    Ilchenko, Nadia O.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Geminal difluorination of alpha,alpha '-disubstituted styrenes using fluoro-benziodoxole reagent. Migration aptitude of the alpha-substituents2017In: Journal of fluorine chemistry, ISSN 0022-1139, E-ISSN 1873-3328, Vol. 203, p. 104-109Article in journal (Refereed)
    Abstract [en]

    alpha,alpha'-Disubstituted styrenes undergo a difluorination-rearrangement reaction with fluoro-benzoiodoxole reagent 1. The reaction is catalyzed by Pd(MeCN)(4)(BF4)(2) and Cu(MeCN)(4)PF6. We have studied the rearrangement of alpha,alpha'-diaryl substituted styrenes, in which the aryl groups have different electronic character. In the case of a aryl, alpha'-alkyl substituted styrenes, the aryl substituent has a higher migratory aptitude than the alkyl group. We have also extended the reactions to cycloalkyl styrenes, which underwent interesting ring contraction/expansion reactions. The regioselectivity of the migration can be explained on the basis of the formation of a phenonium intermediate.

  • 35.
    Iqbal, M. Naeem
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Abdel-Magied, Ahmed F.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Abdelhamid, Hani Nasser
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Olsén, Peter
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Shatskiy, Andrey
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mesoporous Ruthenium Oxide: A Heterogeneous Catalyst for Water Oxidation2017In: ACS Sustainable Chemistry & Engineering, ISSN 2168-0485, Vol. 5, no 11, p. 9651-9656Article in journal (Refereed)
    Abstract [en]

    Herein we report the synthesis of mesoporous ruthenium oxide (MP-RuO2) using a template-based approach. The catalytic efficiency of the prepared MP-RuO2 was compared to commercially available ruthenium oxide nanoparticles (C-RuO2) as heterogeneous catalysts for water oxidation. The results demonstrated superior performance of MP-RuO2 for oxygen evolution compared to the C-RuO2 with respect to recyclability, amount of generated oxygen, and stability over several catalytic runs.

  • 36.
    Kalek, Marcin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry. California Institute of Technology, United States; University of Warsaw, Poland.
    Fu, Gregory C.
    Caution in the Use of Nonlinear Effects as a Mechanistic Tool for Catalytic Enantioconvergent Reactions: Intrinsic Negative Nonlinear Effects in the Absence of Higher-Order Species2017In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 139, no 11, p. 4225-4229Article in journal (Refereed)
    Abstract [en]

    Investigation of the dependence of product enantiometric excess (ee) on catalyst ee is a widely used tool to probe the mechanism of an enantioselective reaction; in particular, the observation of a nonlinear relationship is usually interpreted as an indication of the presence of one or more species that contain at least two units of the chiral entity. In this report, we demonstrate that catalytic enantioconvergent reactions can display an intrinsic negative nonlinear effect that originates purely from the kinetic characteristics of certain enantioconvergent processes and is independent of possible aggregation of the chiral entity. Specifically, this intrinsic negative nonlinear effect can arise when there is a kinetic resolution of the racemic starting material, and its magnitude is correlated with the selectivity factor and the conversion; the dependence on conversion provides a ready means to distinguish it from a more conventional nonlinear effect. We support our analysis with experimental data for two distinct enantioconvergent processes, catalyzed by a chiral phosphine and the other by a chiral Pd/phosphine complex.

  • 37. Kalek, Marcin
    et al.
    Himo, Fahmi
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mechanism and Selectivity of Cooperatively Catalyzed Meyer-Schuster Rearrangement/Tsuji-Trost Allylic Substitution. Evaluation of Synergistic Catalysis by Means of Combined DFT and Kinetics Simulations2017In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 139, no 30, p. 10250-10266Article in journal (Refereed)
    Abstract [en]

    The reaction between propargylic alcohols and allylic carbonates, engaging vanadium and palladium catalysts, is an exemplary case of a cooperatively catalyzed process. This combined Meyer-Schuster rearrangement/Tsuji-Trost allylic substitution clearly illustrates the enormous advantages offered by the simultaneous use of two catalysts, but also the inherent challenges regarding selectivity associated with such a reaction design. These challenges originate from the fact that the desired product of the combined process is formed by a bimolecular coupling of the two substrates activated by the respective catalysts. However, these two processes may also occur in a detached way via the reactions of the catalytic intermediates with the starting propargylic alcohol present in the reaction mixture, leading to the formation of two side-products. Herein, we investigate the overall mechanism of this reaction using density functional theory (DFT) methodology. The mechanistic details of the catalytic cycles for all the individual processes are established. In particular, it is shown that the diphosphine ligand, dppm, used in the reaction promotes the formation of dinuclear palladium complexes, wherein only a single metal center is directly involved in the catalysis. Due to the complexity of the combined reaction network, kinetics simulation techniques are employed in order to analyze the overall selectivity. The simulations directly link the results of the DFT calculations with the experimental data and confirm that the computed free energy profiles indeed reproduce the observed selectivities. In addition, a sensitivity analysis is carried out to assess the importance of the individual steps on the product distribution. The observed behavior of the kinetic network is rationalized, and trends in the reaction outcome upon changing the initial conditions, such as the catalysts amounts and ratio, are discussed. The results provide a general framework for understanding the factors governing the selectivity of the cooperatively catalyzed reactions.

  • 38.
    Kumaniaev, Ivan
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Subbotina, Elena
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sävmarker, Jonas
    Larhed, Mats
    Galkin, Maxim V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Samec, Joseph S. M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lignin depolymerization to monophenolic compounds in a flow-through system2017In: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270, Vol. 19, no 24, p. 5767-5771Article in journal (Refereed)
    Abstract [en]

    A reductive lignocellulose fractionation in a flow-through system in which pulping and transfer hydrogenolysis steps were separated in time and space has been developed. Without the hydrogenolysis step or addition of trapping agents to the pulping, it is possible to obtain partially depolymerized lignin (21 wt% monophenolic compounds) that is prone to further processing. By applying a transfer hydrogenolysis step 37 wt% yield of lignin derived monophenolic compounds was obtained. Pulp generated in the process was enzymatically hydrolyzed to glucose in 87 wt% yield without prior purification.

  • 39.
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Photochemical Generation of Nitrogen-Centered Amidyl, Hydrazonyl, and Imidyl Radicals: Methodology Developments and Catalytic Applications2017In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 7, no 8, p. 4999-5022Article in journal (Refereed)
    Abstract [en]

    During the past decade, visible light photo catalysis has become a powerful synthetic platform for promoting challenging bond constructions under mild reaction conditions. These photocatalytic systems rely on harnessing visible light energy for synthetic purposes through the generation of reactive but controllable free radical species. Recent progress in the area of visible light photocatalysis has established it as an enabling catalytic strategy for the mild and selective generation of nitrogen-centered radicals. The application of visible light for photocatalytic activation of amides, hydrazones, and imides represents a valuable approach for facilitating the formation of nitrogen-centered radicals. Within the span of only a couple of years, significant progress has been made for expediting the generation of amidyl, hydrazonyl, and imidyl radicals from a variety of precursors. This Perspective highlights the recent advances in visible light-mediated generation of these radicals. A particular emphasis is placed on the unique ability of visible light photocatalysis in accessing elusive reaction manifolds for the construction of diversely functionalized nitrogen-containing motifs and as a platform for nontraditional bond disconnections in contemporary synthetic chemistry.

  • 40. Li, Ying-Ying
    et al.
    Ye, Ke
    Siegbahn, Per E. M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Liao, Rong-Zhen
    Mechanism of Water Oxidation Catalyzed by a Mononuclear Manganese Complex2017In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 10, no 5, p. 903-911Article in journal (Refereed)
    Abstract [en]

    The design and synthesis of biomimetic Mn complexes to catalyze oxygen evolution is a very appealing goal because water oxidation in nature employs a Mn complex. Recently, the mononuclear Mn complex [LMnII(H2O)(2)](2+) [1, L=Py2N(tBu)(2), Py= pyridyl] was reported to catalyze water oxidation electro-chemically at an applied potential of 1.23 V at pH 12.2 in aqueous solution. Density functional calculations were performed to elucidate the mechanism of water oxidation promoted by this catalyst. The calculations showed that 1 can lose two protons and one electron readily to produce [LMnIII(OH)(2)](+) (2), which then undergoes two sequential proton-coupled electron-transfer processes to afford [(LMnOO)-O-V](+) (4). The O-O bond formation can occur through direct coupling of the two oxido ligands or through nucleophilic attack of water. These two mechanisms have similar barriers of approximately 17 kcal mol(-1). The further oxidation of 4 to generate [(LMnO)-O-VI-O](2+) (5), which enables O-O bond formation, has a much higher barrier. In addition, ligand degradation by C-H activation has a similar barrier to that for the O-O bond formation, and this explains the relatively low turnover number of this catalyst.

  • 41. Liao, Rong-Zhen
    et al.
    Siegbahn, Per E. M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Possible water association and oxidation mechanisms for a recently synthesized Mn4Ca-complex2017In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 354, p. 169-181Article in journal (Refereed)
    Abstract [en]

    The laboratory synthesis of complexes to mimic the structure of the Mn4Ca cluster in the oxygen evolving complex (OEC) of photosystem II is a very challenging task to accomplish. The most encouraging breakthrough in this field was recently achieved with the synthesis of a Mn4Ca complex (Zhang et al., 2015) that shows a very similar core structure to the OEC. On the basis of density functional calculations, the structure and the redox potentials of this Mn4Ca complex in acetonitrile are obtained with very good agreement to experiments. A possible mechanism for water oxidation is more problematic. If only the thermodynamics is considered and assuming a standard state of 1 mol/L, it turns out that up to five water molecules can be inserted into the complex with only a small cost. This leads to a barrier for O-O bond formation which is 22.8 kcal/mol with an applied potential of 1.3 V. However, a study of the kinetics for the insertion of the critical water bridge between Mn3 and Mn4 indicates that the barrier for that process is quite high with 24.6 kcal/mol. A model where this water is not inserted also led to a rather high barrier for O-O bond formation with 31.7 kcal/mol with an applied potential of 1.3 V. However, the barrier decreases significantly to only 13.4 kcal/mol with an applied potential of 1.7 V. The different barrier originates from the different energetic penalty for the formation of the catalytic competent S-4 state. A major experimental problem discussed below, is the instability of the complex, which does not allow a high water concentration. The best calculated overall mechanism obtained is essentially the same as the leading suggestion for the OEC, where the critical O-O bond formation takes place at the S-4 state (formally Mn-4(IV,IV,IV,IV)) via direct coupling of a Mn-IV-oxyl radical and a di-Mn bridging oxo group.

  • 42.
    Lindstedt, Erik
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Reitti, Marcus
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    One-Pot Synthesis of Unsymmetric Diaryliodonium Salts from Iodine and Arenes2017In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 82, no 22, p. 11909-11914Article in journal (Refereed)
    Abstract [en]

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

  • 43.
    Liu, Jianguo
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Krajangsri, Suppachai
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Singh, Thishana
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    De Seriis, Giulia
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Chumnanvej, Napasawan
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Wu, Haibo
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Andersson, Pher G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Regioselective Iridium-Catalyzed Asymmetric Monohydrogenation of 1,4-Dienes2017In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 139, no 41, p. 14470-14475Article in journal (Refereed)
    Abstract [en]

    A highly efficient regio- and enantioselective monohydrogenation of 1,4-dienes has been realized using an iridium catalyst with a chiral N,P-ligand under mild conditions. The substrate scope was studied and included both unfunctionalized as well as functionalized substituents on the meta- or para-position. Substrates having substituents with functionalities such as silyl protected alcohols or ketals were monohydrogenated in high regioselectivity and high enantiomeric excess (up to 98% ee).

  • 44.
    Lundberg, Helena
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Tinnis, Fredrik
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhang, Jiji
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Algarra, Andrés G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Universidad de Cádiz, Spain.
    Himo, Fahmi
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Adolfsson, Hans
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Umeå University, Sweden.
    Mechanistic Elucidation of Zirconium-Catalyzed Direct Amidation2017In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 139, no 6, p. 2286-2295Article in journal (Refereed)
    Abstract [en]

    The mechanism of the zirconium-catalyzed condensation of carboxylic acids and amines for direct formation of amides was studied using kinetics, NMR spectroscopy, and DFT calculations. The reaction is found to be first order with respect to the catalyst and has a positive rate dependence on amine concentration. A negative rate dependence on carboxylic acid concentration is observed along with S-shaped kinetic profiles under certain conditions, which is consistent with the formation of reversible off-cycle species. Kinetic experiments using reaction progress kinetic analysis protocols demonstrate that inhibition of the catalyst by the amide product can be avoided using a high amine concentration. These insights led to the design of a reaction protocol with improved yields and a decrease in catalyst loading. NMR spectroscopy provides important details of the nature of the zirconium catalyst and serves as the starting point for a theoretical study of the catalytic cycle using DFT calculations. These studies indicate that a dinuclear zirconium species can catalyze the reaction with feasible energy barriers. The amine is proposed to perform a nucleophilic attack at a terminal eta(2)-carboxylate ligand of the zirconium catalyst, followed by a C-O bond cleavage step, with an intermediate proton transfer from nitrogen to oxygen facilitated by an additional equivalent of amine. In addition, the DFT calculations reproduce experimentally observed effects on reaction rate, induced by electronically different substituents on the carboxylic acid.

  • 45.
    Lübcke, Marvin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Karolinska Institutet, Sweden.
    Yuan, Weiming
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Karolinska Institutet, Sweden.
    Trifluoromethylthiolation-Based Bifunctionalization of Diazocarbonyl Compounds by Rhodium Catalysis2017In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 19, no 17, p. 4548-4551Article in journal (Refereed)
    Abstract [en]

    A new Rh-catalyzed, three-component reaction for the oxytrifluoromethylthiolation of alpha-diazoketones was developed. The SCF3 functionality was introduced using a stable dibenzenesulfonimide reagent under mild conditions. Alcohols, acetals, and ethers were used as the alkoxy sources. Cyclic ethers underwent a trifunctionalization reaction through the introduction of SCF3, OR, and N(SO2Ph)(2) substituents in a single step.

  • 46. Mahanti, Bani
    et al.
    González Miera, Greco
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martínez-Castro, Elisa
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bedin, Michele
    Martín-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ott, Sascha
    Thapper, Anders
    Homogeneous Water Oxidation by Half-Sandwich Iridium(III) N-Heterocyclic Carbene Complexes with Pendant Hydroxy and Amino Groups2017In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 10, no 22, p. 4616-4623Article in journal (Refereed)
    Abstract [en]

    Herein, we report three (IrCp)-Cp-III* complexes with hydroxy-or amino-functionalized N-heterocyclic carbene (NHC) ligands that catalyze efficient water oxidation induced by addition of ceric ammonium nitrate (CAN). The pendant hydroxy or amino groups are very important for activity, and the complexes with heteroatom-functionalized NHC ligands show up to 15 times higher rates of oxygen evolution in CAN-induced water oxidation than a reference (IrCp)-Cp-III* complex without heteroatom functionalization. The formation of molecular high-valent Ir intermediates that are presumably involved in the rate-determining step for water oxidation is established by UV/Vis spectroscopy and ESI-MS under turnover conditions. The hydroxy groups on the NHC ligands, as well as chloride ligands on the iridium center are proposed to structurally stabilize the highvalent species, and thereby improve the catalytic activity. The Ir-III complex with a hydroxy-functionalized NHC shows the highest catalytic activity with a TON of 2500 obtained in 3 h and with >90% yield relative to the amount of oxidant used.

  • 47.
    Manta, Bianca
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Engelmark Cassimjee, Karim
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Himo, Fahmi
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Quantum Chemical Study of Dual-Substrate Recognition in ω-Transaminase2017In: ACS Omega, E-ISSN 2470-1343, Vol. 2, no 3, p. 890-898Article in journal (Refereed)
    Abstract [en]

    ω-Transaminases are attractive biocatalysts for the production of chiral amines. These enzymes usually have a broad substrate range. Their substrates include hydrophobic amines as well as amino acids, a feature referred to as dual-substrate recognition. In the present study, the reaction mechanism for the half-transamination of L-alanine to pyruvate in (S)-selective Chromobacterium violaceum ω-transaminase is investigated using density functional theory calculations. The role of a flexible arginine residue, Arg416, in the dual-substrate recognition is investigated by employing two active-site models, one including this residue and one lacking it. The results of this study are compared to those of the mechanism of the conversion of (S)-1-phenylethylamine to acetophenone. The calculations suggest that the deaminations of amino acids and hydrophobic amines follow essentially the same mechanism, but the energetics of the reactions differ significantly. It is shown that the amine is kinetically favored in the half-transamination of L-alanine/pyruvate, whereas the ketone is kinetically favored in the half-transamination of (S)-1-phenylethylamine/acetophenone. The calculations further support the proposal that the arginine residue facilitates the dual-substrate recognition by functioning as an arginine switch, where the side chain is positioned inside or outside of the active site depending on the substrate. Arg416 participates in the binding of L-alanine by forming a salt bridge to the carboxylate moiety, whereas the conversion of (S)-1-phenylethylamine is feasible in the absence of Arg416, which here represents the case in which the side chain of Arg416 is positioned outside of the active site.

  • 48. Mao, Lujia
    et al.
    Bertermann, Rüdiger
    Emmert, Katharina
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Marder, Todd B.
    Synthesis of Vinyl-, Allyl-, and 2-Boryl Allylboronates via a Highly Selective Copper-Catalyzed Borylation of Propargylic Alcohols2017In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 19, no 24, p. 6586-6589Article in journal (Refereed)
    Abstract [en]

    An efficient methodology for the synthesis of vinyl-, allyl-, and (E)-2-boryl allylboronates from propargylic alcohols via Cu-catalyzed borylation under mild conditions is reported. In the presence of commercially available Cu(OAc)(2) or Cu(acac)(2) and Xantphos, the reaction affords the desired products in up to 92% yield with a broad substrate scope (43 examples). Isolation of an allenyl boronate as the reaction intermediate suggests that an insertion elimination-type reaction, followed by borylcupration, is involved in the borylation of propargylic alcohols.

  • 49. Mao, Lujia
    et al.
    Bertermann, Rüdiger
    Rachor, Simon G.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Marder, Todd B.
    Palladium-Catalyzed Oxidative Borylation of Allylic C-H Bonds in Alkenes2017In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 19, no 24, p. 6590-6593Article in journal (Refereed)
    Abstract [en]

    This communication describes an efficient palladium pincer complex-catalyzed allylic C-H borylation of alkenes. The transformation exhibits high regio- and stereo selectivity with a variety of linear alkenes. A synthetically useful feature of this allylic C-H borylation method is that all allyl-Bpin products can be isolated in usually high yields. Preliminary mechanistic studies indicate that this CH borylation reaction proceeds via Pd(IV) pincer complex intermediates.

  • 50. Mao, Lujia
    et al.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Marder, Todd B.
    Synthesis of Benzyl-, Allyl-, and Allenyl-boronates via Copper-Catalyzed Borylation of Alcohols2017In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 19, no 5, p. 1204-1207Article in journal (Refereed)
    Abstract [en]

    Alcohols are among the most abundant and readily available organic feedstocks in industrial processes. The direct catalytic functionalization of sp(3) C-O bonds of alcohols remains the main challenge in this field. Here, we report a copper-catalyzed synthesis of benzyl-, allyl-, and allenylboronates from benzylic, allylic, and propargylic alcohols, respectively. This protocol exhibits a broad reaction scope (40 examples) and high efficiency (up to 95% yield) under mild conditions, including for the preparation of secondary allylic boronates. Preliminarily mechanistic studies suggest that nucleophilic substitution is involved in this reaction.

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