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  • 1.
    Alam, Rauful
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Catalytic Regio- and Stereoselective Reactions for the Synthesis of Allylic and Homoallylic Compounds2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is focused on two main areas of organic synthesis, palladium-catalyzed functionalization of alkenes and allylic alcohols, as well as development of new allylboration reactions.

    We have developed a palladium-catalyzed selective allylic trifluoroacetoxylation reaction based on C−H functionalization. Allylic trifluoroacetates were synthesized from functionalized olefins under oxidative conditions. The reactions proceed under mild conditions with a high level of diastereoselectivity. Mechanistic studies of the allylic C−H trifluoroacetoxylation indicate that the reaction proceeds via (η3-allyl)palladium(IV) intermediate.

    Palladium-catalyzed regio- and stereoselective synthesis of allylboronic acids from allylic alcohols has been demonstrated. Diboronic acid B2(OH)4 was used as the boron source in this process.

    The reactivity of the allylboronic acids were studied in three types of allylboration reactions: allylboration of ketones, imines and acyl hydrazones. All three processes are conducted under mild conditions without any additives. The reactions proceeded with remarkably high regio- and stereoselectivity.

    An asymmetric version of the allylboration of ketones was also developed. In this process chiral BINOL derivatives were used as catalysts. The reaction using γ-disubstituted allylboronic acids and various aromatic and aliphatic ketones afforded homoallylic alcohols bearing two adjacent quaternary stereocenters with excellent regio-, diastereo- and enantioselectivity (up to 97:3 er) in high yield. The stereoselectivity in the allylboration reactions could be rationalized on the basis of the Zimmerman-Traxler TS model.

  • 2.
    Angles d'Ortoli, Thibault
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sjöberg, Nils A.
    Vasiljeva, Polina
    Lindman, Jonas
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bergenstråhle-Wohlert, Malin
    Wohlert, Jakob
    Temperature Dependence of Hydroxymethyl Group Rotamer Populations in Cellooligomers2015In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 119, no 30, p. 9559-9570Article in journal (Refereed)
    Abstract [en]

    Empirical force fields for computer simulations of carbohydrates are often implicitly assumed to be valid also at temperatures different from room temperature for which they were optimited: Herein, the temperature dependence of the hydroxymethyl group rotamer populations in short oligogaccharides is invegtigated using Molecular dynamics simulations and NMR spectroscopy. Two oligosaccharides, methyl beta-cellobioside and beta-cellotetraose were simulated using three different carbohydrate force fields (CHARMM C35, GLYCAM06, and GROMOS 56A(carbo)) in combination with different water models (SPC, SPC/E, and TIP3P) using replica exchange molecular dynamics simulations. For comparison, hydroxymethyl group rotamer populations were investigated for methyl beta-cellobioside and cellopentaose based- on measured NMR (3)J(H5,H6) coupling constants, in the latter case by using a chemical shift selective NMR-filter. Molecular dynamics simulations in combination with NMR spectroscopy show that the temperature dependence of the hydroxymethyl rotamer population in these short cellooligomers, in the range 263-344 K, generally becomes exaggerated in simulations when compared to experimental data, but also that it is dependent on simulation conditions, and most notably properties of the water model.

  • 3.
    Bartoszewicz, Agnieszka
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    González Miera, Greco
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Marcos, Rocio
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Norrby, Per-Ola
    Martín-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mechanistic Studies on the Alkylation of Amines with Alcohols Catalyzed by a Bifunctional Iridium Complex2015In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 5, no 6, p. 3704-3716Article in journal (Refereed)
    Abstract [en]

    The mechanism of the N-alkylation of amines with alcohols catalyzed by an iridium complex containing an N-heterocyclic carbene (NHC) ligand with a tethered alcohol/alkoxide functionality was investigated by a combination of experimental and computational methods. The catalyst resting state is an iridium hydride species containing the amine substrate as a ligand, and decoordination of the amine, followed by coordination of the imine intermediate to the iridium center, constitute the rate-determining step (rds) of the catalytic process. The alcohol/alkoxide that is tethered to the NHC participates in every step of the catalytic cycle by accepting or releasing protons and forming hydrogen bonds with the reacting species. Thus, the iridium complex with the alcohol/alkoxide tethered to the N-heterocyclic carbene ligand acts as a bifunctional catalyst.

  • 4. Brown, Michael
    et al.
    Delorme, Marion
    Malmedy, Florence
    Malmgren, Joel
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Wirth, Thomas
    Synthesis of New Chiral Diaryliodonium Salts2015In: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry, ISSN 0936-5214, E-ISSN 1437-2096, Vol. 26, no 11, p. 1573-1577Article in journal (Refereed)
    Abstract [en]

    A structurally diverse range of chiral diaryliodonium salts have been synthesised which have potential application in metal-free stereoselective arylation reactions.

  • 5.
    Carson, Fabian
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Martínez-Castro, Elisa
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Marcos, Rocio
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    González Miera, Greco
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Jansson, Kjell
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Martin-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Effect of the functionalisation route on a Zr-MOF with an Ir-NHC complex for catalysis2015In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 51, no 54, p. 10864-10867Article in journal (Refereed)
    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.

  • 6.
    Dey, Chandan
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lindstedt, Erik
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Wallenberg Research Centre at Stellenbosch University, South Africa.
    Metal-Free C-Arylation of Nitro Compounds with Diaryliodonium Salts2015In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 17, no 18, p. 4554-4557Article in journal (Refereed)
    Abstract [en]

    An efficient, mild, and metal-free arylation of nitro-alkanes with diaryliodonium salts has been developed, giving easy access to tertiary nitro compounds. The reaction proceeds in high yields without the need for excess reagents and can be extended to alpha-arylation of nitroesters. Nitroalkanes were selectively C-arylated in the presence of other easily arylated functional groups, such as phenols and aliphatic alcohols.

  • 7.
    Engström, Olof
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Exploring the Molecular Behavior of Carbohydrates by NMR Spectroscopy: Shapes, motions and interactions2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Carbohydrates are essential biomolecules that decorate cell membranes and proteins in organisms. They are important both as structural elements and as identification markers. Many biological and pathogenic processes rely on the identification of carbohydrates by proteins, thereby making them attractive as molecular blueprints for drugs. This thesis describes how NMR spectroscopy can be utilized to study carbohydrates in solution at a molecular level. This versatile technique facilitates for investigations of (i) shapes, (ii) motions and (iii) interactions.

    A conformational study of an E. coli O-antigen was performed by calculating atomic distances from NMR NOESY experiments. The acquired data was utilized to validate MD simulations of the LPS embedded in a membrane. The agreement between experimental and calculated data was good and deviations were proven to arise from spin-diffusion. In another study presented herein, both the conformation and the dynamic behavior of amide side-chains linked to derivatives of D-Fucp3N, a sugar found in the O-antigen of bacteria, were investigated. J-couplings facilitated a conformational analysis and 13C saturation transfer NMR experiments were utilized to measure rate constants of amide cis-trans isomerizations.

    13C NMR relaxation and 1H PFG diffusion measurements were carried out to explore and describe the molecular motion of mannofullerenes. The dominating motions of the mannofullerene spectral density were found to be related to pulsating motions of the linkers rather than global rotational diffusion. The promising inhibition of Ebola viruses identified for a larger mannofullerene can thus be explained by an efficient rebinding mechanism that arises from the observed flexibility in the linker.

    Molecular interactions between sugars and caffeine in water were studied by monitoring chemical shift displacements in titrations. The magnitude of the chemical shift displacements indicate that the binding occurs by a face to face stacking of the aromatic plane of caffeine to the ring plane of the sugar, and that the interaction is at least partly driven by solvation effects. Also, the binding of a Shigella flexneri serotype Y octasaccharide to a bacteriophage Sf6 tail spike protein was investigated. This interaction was studied by 1H STD NMR and trNOESY experiments. A quantitative analysis of the STD data was performed employing a newly developed method, CORCEMA-ST-CSD, that is able to simulate STD data more accurately since the line broadening of protein resonances are accounted for in the calculations.

  • 8.
    Lind, Maria E. S.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Quantum Chemical Modeling of Asymmetric Enzymatic Reactions2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Computational methods are very useful tools in the study of enzymatic reactions, as they can provide a detailed understanding of reaction mechanisms and the sources of various selectivities. In this thesis, density functional theory has been employed to examine four different enzymes of potential importance for biocatalytic applications. The enzymes considered are limonene epoxide hydrolase, soluble epoxide hydrolase, arylmalonate decarboxylase and phenolic acid decarboxylase. Besides the reaction mechanisms, the enantioselectivities in three of these enzymes have also been investigated in detail. In all studies, quite large quantum chemical cluster models of the active sites have been used. In particular, the models have to account for the chiral environment of the active site in order to reproduce and rationalize the experimentally observed selectivities.

    For both epoxide hydrolases, the calculated enantioselectivities are in good agreement with experiments. In addition, explanations for the change in stereochemical outcome for the mutants of limonene epoxide hydrolase, and for the observed enantioconvergency in the soluble epoxide hydrolase are presented.

    The reaction mechanisms of the two decarboxylases are found to involve the formation of an enediolate- or a quinone methide intermediate, supporting thus the main features of the proposed mechanisms in both cases. For arylmalonate decarboxylase, an explanation for the observed enantioselectivity is also presented.

    In addition to the obtained chemical insights, the results presented in this thesis demonstrate that the quantum chemical cluster approach is indeed a valuable tool in the field of asymmetric biocatalysis.

  • 9.
    Lundberg, Helena
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Group (IV) Metal-Catalyzed Direct Amidation: Synthesis and Mechanistic Considerations2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

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

  • 10.
    Nagendiran, Anuja
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Catalytic reactions with palladium supported on mesocellular foam: Applications in hydrogenation, isomerization, and C-C bond forming reactions2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

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

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

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

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

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

  • 11.
    Pascanu, Vlad
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bermejo Gomez, Antonio
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ayats, Carles
    Platero-Prats, Ana Eva
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Carson, Fabian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Su, Jie
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Yao, Qingxia
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Pericas, Miquel A.
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Martin-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Double-Supported Silica-Metal-Organic Framework Palladium Nanocatalyst for the Aerobic Oxidation of Alcohols under Batch and Continuous Flow Regimes2015In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 5, no 2, p. 472-479Article in journal (Refereed)
    Abstract [en]

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

  • 12.
    Pascanu, Vlad
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hansen, Peter R.
    Bermejo Gomez, Antonio
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ayats, Carles
    Platero-Prats, Ana E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Johansson, Magnus J.
    Pericas, Miquel A.
    Martín-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Highly Functionalized Biaryls via Suzuki-Miyaura Cross-Coupling Catalyzed by Pd@MOF under Batch and Continuous Flow Regimes2015In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 8, no 1, p. 123-130Article in journal (Refereed)
    Abstract [en]

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

  • 13.
    Pathipati, Stalin R.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Singh, Vipender
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Selander, Nicklas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lewis Acid Catalyzed Annulation of Nitrones with Oxiranes, Aziridines, and Thiiranes2015In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 17, no 18, p. 4506-4509Article in journal (Refereed)
    Abstract [en]

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

  • 14.
    Peters, Byron
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Iridium Catalysed Asymmetric Hydrogenation of Olefins and Isomerisation of Allylic Alcohols2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

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

  • 15.
    Platero-Prats, Ana E.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Argonne National Laboratory, USA.
    Bermejo Gómez, Antonio
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Chapman, Karena W.
    Martin-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Functionalising metal-organic frameworks with metal complexes: the role of structural dynamics2015In: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, Vol. 17, no 40, p. 7632-7635Article in journal (Refereed)
    Abstract [en]

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

  • 16.
    Platero-Prats, Ana E.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bermejo Gómez, Antonio
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Samain, Louise
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Martin-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    The First One-Pot Synthesis of Metal-Organic Frameworks Functionalised with Two Transition-Metal Complexes2015In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 21, no 2, p. 861-866Article in journal (Refereed)
    Abstract [en]

    The synthesis of a metal-organic framework (UiO-67) functionalised simultaneously with two different transition metal complexes (Ir and Pd or Rh) through a one-pot procedure is reported for the first time. This has been achieved by an iterative modification of the synthesis parameters combined with characterisation of the resulting materials using different techniques, including X-ray absorption spectroscopy (XAS). The method also allows the first synthesis of UiO-67 with a very wide range of loadings (from 4 to 43 mol%) of an iridium complex ([IrCp*(bpydc)(Cl)Cl](2-); bpydc=2,2'-bipyridine-5,5'-dicarboxylate, Cp* = pentamethylcyclopentadienyl) through a pre-functionalisation methodology.

  • 17.
    Pu, Maoping
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Molecular Motion in Frustrated Lewis Pair Chemistry: insights from modelling2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Mechanisms of reactions of the frustrated Lewis pairs (FLPs) with carbon dioxide (CO2) and hydrogen (H2) are studied by using quantum chemical modelling. FLPs are relatively novel chemical systems in which steric effects prevent a Lewis base (LB) from donating its electron pair to a Lewis acid (LA). From the main group of the periodic table, a variety of the electron pair donors and acceptors can create an FLP and the scope of the FLP chemistry is rapidly expanding at present. Representative intermolecular FLPs are phosphines and boranes with bulky electron-donating groups on phosphorus and bulky electron-withdrawing groups on boron – e.g., the tBu3P/B(C6F5)3 pair. The intramolecular FLPs feature linked LB and LA centers in one molecule.

    Investigations of the FLP reaction mechanisms were carried out using the transition state (TS) and the potential energy surface (PES) calculations plus the Born-Oppenheimer molecular dynamics (BOMD) as an efficient and robust implementation of general ab initio molecular dynamics scheme. In BOMD simulations, quantum and classical mechanics are combined. The electronic structure calculations are fully quantum via the density functional theory (DFT). Molecular motion at finite (non-zero) temperature is explicitly accounted for at non-quantized level via Newton’s equations. Due to recent advancements of computers and algorithms, one can treat fairly large macromolecular systems with BOMD and even include significant portion of the first solvation shell surrounding a large reacting complex in the molecular model.

    Main results are as follows. It is shown that dynamics is significant for understanding of FLP chemistry. The multiscale nature of motion – i.e., light molecules such as CO2 or H2 versus a pair of heavy LB and LA molecules – affects the evolution of interactions in the reacting complex. Motion which is perpendicular to the reaction coordinate was found to play a role in the transit of the activated complex through the TS-region. Regarding the heterolytic cleavage of H2 by tBu3P/B(C6F5)3 FLP simulated in gas phase and with explicit solvent, it was found that (i) the reaction path includes shallow quasi-minima “imbedded” in the TS-region, and (ii) tBu3P/B(C6F5)3 are almost stationary while proton- and hydride-like fragments of H2 move toward phosphorous and boron respectively. For binding of CO2 by tBu3P/B(C6F5)3 FLP, it was found that (i) the reacting complex can “wander” along the “potential energy wall” that temporarily blocks the path to the product, and (ii) the mechanism can combine the concerted and two-step reaction paths in solution. The discovered two-step binding of CO2 by tBu3P/B(C6F5)3 FLP involves solvent-stabilized phosphorus-carbon interactions (dative bonding). These and other presented results are corroborated and explained using TS and PES calculations. With computations of observable characteristics of reactions, it is pointed out how it could be possible to attain experimental proof of the results.

  • 18.
    Quan, Xu
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hydrogenation, Transfer Hydrogenation and Hydrogen Transfer Reactions Catalyzed by Iridium Complexes2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

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

  • 19.
    Tinnis, Fredrik
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Stridfeldt, Elin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lundberg, Helena
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Adolfsson, Hans
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Stellenbosch University, South Africa.
    Metal-Free N-Arylation of Secondary Amides at Room Temperature2015In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 17, no 11, p. 2688-2691Article in journal (Refereed)
    Abstract [en]

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

  • 20.
    van der Werf, Angela
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Selander, Nicklas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Para-Selective Halogenation of Nitrosoarenes with Copper(II) Halides2015In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 17, no 24, p. 6210-6213Article in journal (Refereed)
    Abstract [en]

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

  • 21.
    Vazquez-Romero, Ana
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bermejo Gomez, Antonio
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martin-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Acid- and Iridium-Catalyzed Tandem 1,3-Transposition/3,1-Hydrogen Shift/Chlorination of Allylic Alcohols2015In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 5, no 2, p. 708-714Article in journal (Refereed)
    Abstract [en]

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

  • 22.
    Wikmark, Ylva
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Engineering Candida antarctica Lipase A for Enantioselective Transformations in Organic Synthesis: Design, Immobilization and Organic Solvent Screening of Smart Enzyme Libraries2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The use of enzymes as catalysts in organic synthesis constitutes an attractive alternative to conventional chemical catalysis. Enzymes are non-toxic and biodegradable and they can operate under mild reaction conditions. Furthermore, they often display high chemo-, regio- and stereoselectivity, enabling specific reactions with single product outcome.

    By the use of protein engineering, enzymes can be altered for the specific needs of the researcher. The major part of this thesis describes engineering of lipase A from Candida antarctica (CalA), for improved enantioselectivity in organic synthetic transformations.

    The first part of the thesis describes a highly combinatorial method for the introduction of mutation sites in an enzyme library. By the simultaneous introduction of nine mutations, we found an enzyme variant with five out of the nine possible mutations. This quintuple variant had an enlarged active site pocket and was enantioselective and active for our model substrate, an ibuprofen ester. This is a bulky substrate for which the wild-type enzyme shows no enantioselectivity and very poor activity.

    In the second part of the thesis, we continued our approach of combinatorial, focused enzyme libraries. This time we aimed at decreasing the alcohol pocket of CalA, in order to increase the enantioselectivity for small and medium-sized secondary alcohols. The enzyme library was bound on microtiter plates and screened by a transacylation reaction in organic solvent. This library yielded an enzyme variant with high enantioselectivity for the model substrate 1-phenyl ethanol, and high to excellent selectivity for other alcohols tested. Screening in organic solvent is advantageous since a potential hit is more synthetically useful.

    In the third part of the thesis, we used manipulated beads of controlled porosity glass (EziG™) for enzyme immobilization, and demonstrated the generality of this carrier for several enzyme classes. EziG™ allowed fast enzyme immobilization with simultaneous purification and yielded active biocatalysts in all cases.

    The last project describes the function of the proposed active site flap in CalA. In our study, we removed this motif. The engineered variant was compared to the wild-type enzyme by testing the amount of interfacial activation and the selectivity for certain alcohols. We showed that the motif is indeed controlling the entrance to the active site and that the flap is not part of the enantioselectivity determining machinery. 

  • 23.
    Yao, Qingxia
    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.
    Su, Jie
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Pascanu, Vlad
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Yun, Yifeng
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zheng, Haoquan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Chen, Hong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Liu, Leifeng
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Abdelhamid, Hani Nasser
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Martin-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Series of Highly Stable Isoreticular Lanthanide Metal-Organic Frameworks with Expanding Pore Size and Tunable Luminescent Properties2015In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 27, no 15, p. 5332-5339Article in journal (Refereed)
    Abstract [en]

    A series of highly porous isoreticular lanthanide-based metal organic frameworks (LnMOFs) denoted as SUMOE-7I to SUMOE-7IV (SU = Stockholm University; Ln = La, Ce, Pr, Nd, Sm, Eu, and Gd) have been synthesized using tritopic carboxylates as the organic linkers. The SUMOF-7 materials display one-dimensional pseudohexagonal channels with the pore diameter gradually enlarged from 8.4 to 23.9 angstrom, as a result of increasing sizes of the organic linkers. The structures have been solved by single crystal X-ray diffraction or rotation electron diffraction (RED) combined with powder X-ray diffraction (PXRD). The SUMOF-7 materials exhibit robust architectures with permanent porosity. More importantly, they exhibit exceptionally high thermal and chemical stability. We show that, by inclusion of organic dye molecules, the luminescence properties of the MOFs can be elaborated and modulated, leading to promising applications in sensing and optics.

  • 24.
    Zhao, Tony
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of functionalized allylic, propargylic and allenylic compounds: Selective formation of C–B, C–C, C–CF3 and C-Si bonds2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is focused on the development of new palladium and copper- mediated reactions for functionalization of alkenes and propargylic alcohol derivatives. The synthetic utility of the 1,2-diborylated butadienes synthesized in one of these processes has also been demonstrated.

    We have developed an efficient procedure for the synthesis of allenyl boronates from propargylic carbonates and acetates. This was achieved by using a bimetallic system of palladium and copper or silver as co-catalyst. The reactions were performed under mild conditions for the synthesis of a variety of allenyl boronates. Furthermore, the synthesis of 1,2-diborylated butadienes was achieved with high diastereoselectivity from propargylic epoxides. The reactivity of the 1,2-diborylated butadienes with aldehydes was studied. It was found that the initial allylboration reaction proceeds via an allenylboronate intermediate. The allenylboronate reacts readily with an additional aldehyde to construct 2-ethynylbutane-1,4-diols with moderate to high diastereoselectivity.

    We have also studied the copper-mediated trifluoromethylation of propargylic halides and trifluoroacetates. It was also shown that a transfer of chirality occurred when an enantioenriched starting material was used.

    In the last part of the thesis, we have described a method for palladium-catalyzed functionalization of allylic C-H bonds for the selective synthesis of allylic silanes. The protocol only works under highly oxidative conditions which suggest a mechanism involving high oxidation state palladium intermediates.

1 - 24 of 24
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