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  • 301.
    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.

  • 302.
    Heshmat, Mojgan
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Privalov, Timofei
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Structurally Flexible Oxocarbenium/Borohydride Ion Pair: Dynamics of Hydride Transfer on the Background of Conformational Roaming2018In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 122, no 23, p. 5098-5106Article in journal (Refereed)
    Abstract [en]

    We apply Born-Oppenheimer molecular dynamics to the practically significant [dioxane-H(+)-acetone]-[(C6F5)(3)B-H(-)] and [Et2O-H(+)-OCPr2][(C6F5)(3)B-H(-)] ion pair intermediates. Dynamics of hydride transfer in cation/anion ion pair takes place on the background of large amplitude configurational changes. Geometry of oxocarbenium/borohydride ion pairs is flexible, meaning that we uncover significant actual structural disorder at a finite temperature. Therefore, although the starting structure can be fairly close to the configurational area of the hydride transfer transition state (TS) and despite a low potential energy barrier (ca. 1.5 kcal/mol, according to the literature), already at T approximate to 325 K the system can remain ignorant of the TS region and move round and about (roam) in the configurational space for a period of time in the range between 10 and 100 ps. This indicates structural flexibility of oxocarbenium/borohydride ion pair on apparently a flat potential energy landscape of cation/anion interaction, and this has not been taken into consideration by the free energy estimations in static considerations made thus far. The difference between the dynamics-based representation of the system versus the static representation amounts to the difference between quasi-bimolecular versus unimolecular descriptions of the hydride transfer step.

  • 303.
    Heshmat, Mojgan
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Privalov, Timofei
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Surprisingly Flexible Oxonium/Borohydride Ion Pair Configurations2018In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 122, no 15, p. 3713-3727Article in journal (Refereed)
    Abstract [en]

    We investigate the geometry of oxonium/borohydride ion pairs [ether-H(+) ether] [LA-H(-)] with dioxane, THF, and Et2O as ethers and B(C6F5)(3) as the Lewis acid (LA). The question is about possible location of the disolvated proton [ether -H(+) -ether], with respect to the hydride of the structurally complex [LA -H(-)] anion. Using Born Oppenheimer molecular dynamics and a comparison of the potential and free energies of the optimized configurations, we show that herein considered ion pairs are much more flexible geometrically than previously thought. Conformers with different locations of cations with respect to anions are governed by a flat energy -landscape. We found a novel configuration in which oxonium is below [LA-11((-))], with respect to the direction of borane -> hydride vector, and the proton -hydride distance is ca. 6 A. With calculations of the vibrational spectra of [ether-H(+)-ether][(C6F5)(3)B-H(-)] for dioxane, THF, and Et2O as ethers, we investigate the manifestation of SSLB-type (short, strong, low -barrier) hydrogen bonding in the OHO motif of an oxonium cation.

  • 304.
    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.

  • 305.
    Himo, Fahmi
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Recent Trends in Quantum Chemical Modeling of Enzymatic Reactions2017In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 139, no 20, p. 6780-6786Article, review/survey (Refereed)
    Abstract [en]

    The quantum chemical cluster approach is a powerful method for investigating enzymatic reactions. Over the past two decades, a large number of highly diverse systems have been studied and a great wealth of mechanistic insight has been developed using this technique. This Perspective reviews the current status of the methodology. The latest technical developments are highlighted, and challenges are discussed. Some recent applications are presented to illustrate the capabilities and progress of this approach, and likely future directions are outlined.

  • 306.
    Horváth, Attila
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mild and Efficient Palladium(II)-Catalyzed Racemization of Allenes2004In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, no 8, p. 964-965Article in journal (Refereed)
    Abstract [en]

    Allenes undergo racemization in the presence of catalytic amounts of Pd(OAc)2/LiBr under mild conditions; the reaction proceeds via a bromopalladation–debromopalladation sequence and tolerates various functional groups.

     

  • 307.
    Horváth, Attila
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Benner, Jessica
    Simple, Enantiocontrolled Synthesis of 3-Pyrrolines from α-Amino Allenes2004In: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, Vol. 2004, no 15, p. 3240-3243Article in journal (Refereed)
    Abstract [en]

    Cyclization of -amino allenes in the presence of N-bromosuccinimide afforded pyrrolines in good yields. The products were obtained with high enantiomeric excesses when optically active allenes were used as substrates. The synthesis of a 2,5-dehydroprolinol derivative is also presented.

  • 308. 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.

  • 309.
    Huang, Genping
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kalek, Marcin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Himo, Fahmi
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mechanism and Selectivity of Rhodium-Catalyzed 1:2 Coupling of Aldehydes and Allenes2013In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 135, no 20, p. 7647-7659Article in journal (Refereed)
    Abstract [en]

    The rhodium-catalyzed highly regioselective 1:2 coupling of aldehydes and allenes was investigated by means of density functional theory calculations. Full free energy profiles were calculated, and several possible reaction pathways were evaluated. It is shown that the energetically most plausible catalytic cycle is initiated by oxidative coupling of the two allenes, which was found to be the rate-determining step of the overall reaction. Importantly, Rh allyl complexes that are able to adopt both eta(3) and eta(1) configurations were identified as key intermediates present throughout the catalytic cycle with profound implications for the selectivity of the reaction. The calculations reproduced and rationalized the experimentally observed selectivities and provided an explanation for the remarkable alteration in the product distribution when the catalyst precursor is changed from [RhCl(nbd)](2) (nbd = norbornadiene) to complexes containing noncoordinating counterions ([Rh(cod)(2)X]; X = OTf, BF4, PF6; cod = 1,5-cyclooctadiene). It turns out that the overall selectivity of the reaction is controlled by a combination of the inherent selectivities of several of the elementary steps and that both the mechanism and the nature of the selectivity-determining steps change when the catalyst is changed.

  • 310.
    Huang, Genping
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kalek, Marcin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Liao, Rong-Zhen
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Himo, Fahmi
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mechanism, reactivity, and selectivity of the iridium-catalyzed C(sp(3))-H borylation of chlorosilanes2015In: Chemical Science, ISSN 2041-6520, E-ISSN 2041-6539, Vol. 6, no 3, p. 1735-1746Article in journal (Refereed)
    Abstract [en]

    The iridium-catalyzed C(sp(3))-H borylation of methylchlorosilanes is investigated by means of density functional theory, using the B3LYP and M06 functionals. The calculations establish that the resting state of the catalyst is a seven-coordinate Ir(V) species that has to be converted into an Ir(III)tris(boryl) complex in order to effect the oxidative addition of the C-H bond. This is then followed by a C-B reductive elimination to yield the borylated product, and the catalytic cycle is finally completed by the regeneration of the active catalyst over two facile steps. The two employed functionals give somewhat different conclusions concerning the nature of the rate-determining step, and whether reductive elimination occurs directly or after a prior isomerization of the Ir(V) hydride intermediate complex. The calculations reproduce quite well the experimentally-observed trends in the reactivities of substrates with different substituents. It is demonstrated that the reactivity can be correlated to the Ir-C bond dissociation energies of the corresponding Ir(V) hydride intermediates. The effect of the chlorosilyl group is identified to originate from the alpha-carbanion-stabilizing effect of the silicon, which is further reinforced by the presence of an electron-withdrawing chlorine substituent. Furthermore, the source of selectivity for the borylation of primary over secondary C(sp(3))-H can be explained on a steric basis, by repulsion between the alkyl group and the Ir/ligand moiety. Finally, the difference in the reactivity between C(sp(3))-H and C(sp(2))-H borylation is investigated and rationalized in terms of distortion/interaction analysis.

  • 311. Huang, Yong
    et al.
    Gao, Weiming
    Åkermark, Torbjörn
    Li, Mingrun
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    An Air-Stable Fe3S4 Complex with Properties Similar to Those of the HOXair State of the Diiron Hydrogenases2012In: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, no 27, p. 4259-4263Article in journal (Refereed)
    Abstract [en]

    A Fe3S4 complex bridged by azapropanedithiolate (adt), complex 6, was prepared as a potential model of the HOXair state of [FeFe]-hydrogenases. Complex 6 was characterized by IR and 1H NMR spectroscopy, and its structure was determined by X-ray crystallography. The electrochemical studies show that complex 6 is redox-active under acidic conditions, which provides insight into the catalytic mechanism. Hydrogen evolution, driven by visible light, was observed in CH3CN/D2O solution by online mass spectroscopy.

  • 312.
    Ibrahem, Ismail
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Development of organocatalytic asymmetric transformations2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The ability of amino acids and amino acid derivatives to mediate various organocatalytic asymmetric transformations has been investigated and applied in the development of various reactions. This work describes the development of a direct catalytic asymmetric α-aminomethylation of ketones and aldehydes, a catalytic asymmetric aziridination, hydrophosphination and amination of α,β-unsaturated aldehydes.

  • 313. Ibrahem, Ismail
    et al.
    Breistein, Palle
    Cordova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    One-Pot Three-Component Highly Selective Synthesis of Homoallylboronates by Using Metal-Free Catalysis2012In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 18, no 17, p. 5175-5179Article in journal (Refereed)
  • 314. Ibrahem, Ismail
    et al.
    Breistein, Palle
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    One-Pot Three-Component Catalytic Enantioselective Synthesis of Homoallylboronates2011In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 50, no 50, p. 12036-12041Article in journal (Refereed)
  • 315.
    Ibrahem, Ismail
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Casas, Jesus
    Cordova, Armando
    Direct Catalytic Enantioselective a-aminomethylation of ketones2004In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 43, p. 6528-Article in journal (Refereed)
  • 316. Ibrahem, Ismail
    et al.
    Iqbal, Muhammad Naeem
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Verho, Oscar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Eivazihollagh, Alireza
    Olsén, Peter
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Edlund, Håkan
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Norgren, Magnus
    Johnston, Eric V.
    Copper Nanoparticles on Controlled Pore Glass and TEMPO for the Aerobic Oxidation of Alcohols2018In: ChemNanoMat, ISSN 2199-692X, Vol. 4, no 1, p. 71-75Article in journal (Refereed)
    Abstract [en]

    Herein, we report on the facile synthesis of a heterogeneous copper nanocatalyst and its combination with 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) for the aerobic oxidation of alcohols to their corresponding carbonyl compounds. This low cost copper nanocatalyst was found to exhibit excellent recyclability, making it a highly attractive catalytic system from an economical and environmental point of view. Extensive characterization of the catalyst by a number of techniques revealed that it was comprised of well-dispersed Cu(I/II) nanoparticles with an average size of around 6nm.

  • 317. Ibrahem, Ismail
    et al.
    Ma, Guangning
    Afewerki, Samson
    Cordova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium/chiral amine co catalyzed enantioselective beta arylation of alpha,beta unsaturated aldehydes2013In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 52, no 3, p. 878-882Article in journal (Refereed)
  • 318.
    Ibrahem, Ismail
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rios, Ramon
    Vesely, Jan
    Hammar, Peter
    Eriksson, Lars
    Himo, Fahmi
    Cordova, Armando
    Enantioselective Organocatalytic Hydrophosphination of α,β- Unsaturated Aldehydes2007In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 46, p. 4507-Article in journal (Refereed)
  • 319.
    Ibrahem, Ismail
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rios, Ramon
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Vesely, Jan
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhao, Gui-Ling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Cordova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Catalytic enantioselective 5-hydroxyisoxazolidine synthesis: An asymmetric entry to beta-amino acids2008In: Synthesis (Stuttgart), ISSN 0039-7881, E-ISSN 1437-210X, no 7, p. 1153-1157Article in journal (Refereed)
    Abstract [en]

    The highly chemo- and enantioselective organocatalytic tandem reaction between N-carbamate-protected hydroxylamines and a,p-unsaturated aldehydes is presented. The reaction represents a unique entry for the asymmetric synthesis of 5-hydroxyisoxazolidines, oxazolidin-5-ones or gamma-hydroxyamino alcohols in high yields and 90-99% ee. A procedure for the conversion of the oxazolidin-5-ones into the corresponding beta-amino acids is also described.

  • 320.
    Ibrahem, Ismail
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rios, Ramon
    Vesely, Jan
    Zhao, Guiling
    Cordova, Armando
    Organocatalytic Asymmetric 5-Hydroxyisoxazolidine Synthesis: A Highly Enantioselective Route to β-Amino Acids2007In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, p. 849-852Article in journal (Refereed)
  • 321.
    Ibrahem, Ismail
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rios, Ramón
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Vesely, Jan
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hammar, Peter
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Himo, Fahmi
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Enantioselective organocatalytic hydrophosphination of alpha,beta-unsaturated aldehydes2007In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 46, p. 4507-4510Article in journal (Refereed)
  • 322. ibrahem, Ismail
    et al.
    Samec, Joseph S M
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdiva, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Enantioselective addition of aldehydes to amines via combined catalytic biomimetic oxidation and organocatalytic C-C- bond formation2005In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 46, no 23, p. 3965-3968Article in journal (Refereed)
    Abstract [en]

    The biomimetic catalytic enantioselective addition of aldehydes to amines is reported. This was accomplished by combining biomimetic coupled catalytic aerobic oxidation of amines involving ruthenium-induced dehydrogenation and organocatalytic asymmetric Mannich reactions. The novel one-pot reactions furnished β-amino aldehyde and α-amino acid derivatives in high yields with excellent chemoselectivity and up to >99% ee.

  • 323. Ibrahem, Ismail
    et al.
    Santoro, Stefano
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Himo, Fahmi
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Enantioselective conjugate silyl additions to α,β-unsaturated aldehydes catalyzed by combination of transition metal and chiral amine catalysts2011In: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 353, no 2+3, p. 245-252Article in journal (Refereed)
    Abstract [en]

    We report that transition metal-catalyzed nucleophilic activation can be combined with chiral amine-catalyzed iminium activation as exemplified by the unprecedented enantioselective conjugate addition of a dimethylsilanyl group to α,β-unsaturated aldehydes. These reactions proceed with excellent 1,4-selectivity to afford the corresponding β-silyl aldehyde products 3 in high yields and up to 97:3 er using inexpensive bench stable copper salts and simple chiral amine catalysts. The reaction canalso generate a quaternary stereocenter with goodenantioselectivity. Density functional calculations are performed to elucidate the reaction mechanism and the origin of enantioselectivity.

  • 324.
    Ibrahem, Ismail
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhao, Guiling
    Cordova, Armando
    Direct Catalytic Enantioselective α-Aminomethylation of Aldehydes2007In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 13, p. 683-Article in journal (Refereed)
  • 325.
    Ilchenko, Nadia
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Development of Catalytic ElectrophilicTrifluoromethylation and Fluorination Methods2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is focused on development of new catalytic, electrophilic fluorination and trifluoromethylation methods of alkenes. These reactions were carried out using hypervalent trifluoromethyl and fluoroiodine reagents.

    The first project involved copper catalyzed oxytrifluoromethylation of terminal alkenes and alkynes. In this reaction the employed hypervalent iodine underwent a formal addition to C-C multiple bonds. Subsequently, we have also shown that under similar reaction conditions in the presence of B2pin2 as additive quinones can smoothly undergo C-H trifluoromethylation.

    We also developed a cyanotrifluoromethylation reaction of styrenes, which proceds in the presence of copper cyanide and PCy3 as additive. This reaction allows addition of both trifluoromethyl and cyanofunctionality to the styrene, creating two new carbon-carbon bonds.

    The interesting substituent effects and the acceleration of B2pin2 and PCy3 additives inspired us to further investigate the mechanism for the above trifluoromethylation reactions. The Hammett studies showed that the oxytrifluoromethylation reactions are slightly accelerated by electron donor substituents. The C-H trifluoromethylation does not show deuterium isotope effect. Both B2pin2 and PCy3 accelerated the trifluoromethylation reactions but the extent of the acceleration was dependent on the reaction type and on the substituent effects.

    Inspired by our trifluoromethylation results, we have also studied the silver-mediated difluorination of styrenes in the presence of an electrophilic hypervalent iodine based fluorine source. We obtained over 50% of the difluorinated product which suggests that one fluorine atom comes from the fluoroiodine reagent and the other one from BF4-. A phenonium ion intermediate has been proposed to be involved in the mechanism of the difluorination reaction.

  • 326.
    Ilchenko, Nadia O.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Cortes, Miguel A.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium-Catalyzed lodofluorination of Alkenes Using Fluorolodoxole Reagent2016In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 6, no 1, p. 447-450Article in journal (Refereed)
    Abstract [en]

    The application of an air- and moisture-stable fluoroiodane reagent was investigated in the palladium-catalyzed iodofluorination reaction of alkenes. Both the iodo and fluoro substituents arise from the fluoroiodane reagent. In the case of certain palladium catalysts, the alkene substrates undergo allylic rearrangement prior to the iodofluorination process. The reaction is faster for electron-rich alkenes than for electron-deficient ones.

  • 327.
    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.

  • 328.
    Ilchenko, Nadia O.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Janson, Pär G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Copper-Mediated Cyanotrifluoromethylation of Styrenes Using the Togni Reagent2013In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 78, no 21, p. 11087-11091Article in journal (Refereed)
    Abstract [en]

    Styrenes with an electron-deficient double bond undergo cyanotrifluoromethylation with a trifluoromethylated hypervalent iodine reagent in the presence of CuCN. The reaction proceeds under mild conditions in the presence of bulky phosphines or B(2)pin(2) additives. The process is highly regioselective and involves the consecutive formation of two C-C bonds in a single addition reaction. In the presence of a p-methoxy substituent in the styrene, oxytrifluoromethylation occurs instead of the cyanotrifluoromethylation.

  • 329.
    Ilchenko, Nadia O.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Janson, Pär
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Copper-mediated C-H trifluoromethylation of quinones2013In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 49, no 59, p. 6614-6616Article in journal (Refereed)
    Abstract [en]

    Quinones undergo copper-mediated C-H trifluoromethylation reactions using a hypervalent iodine reagent. The reactions have a broad synthetic scope involving naphtho, alkyl, chloro and methoxy quinones.

  • 330.
    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.

  • 331.
    Ioannidis, Panagiotis
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of 5'-C-phosphonomethyl, 2'-C- and 3'-C-branched nucleoside analogues as potential candidates for therapeutic intervention towards HIV1993Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Syntheses of some 5'-C-phosphonomethyl-, 2'-C- and 3'-C-branched nucleoside analogues as potential anti-HIV agents are described. Synthesis of the various nucleoside analogues is based either on the construction of a suitably protected sugar moiety that can be glycosylated with different nucleoside bases by the Vorbrüggen procedure, or on the use of a novel alcohol transposition in the carbohydrate moiety of different 2'-C- or 3'-C-methylene nucleoside analogues, using the reagent system chlorodiphenylphosphine-iodine-imidazole. All target compounds were tested for anti-HIV activity. Of these, only 2',3'-dideoxy-2'-Chydroxymethylcytidine and l-(3,5-dideoxy-ß-D-cryrAro-hexofuranosyl)thymine demonstrated moderate and weak anti-HIV activities, respectively.

  • 332.
    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.

  • 333. Jakhetia, Richa
    et al.
    Marri, Aruna
    Ståhle, Jonas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Verma, Naresh K.
    Serotype-conversion in Shigella flexneri: identification of a novel bacteriophage, Sf101, from a serotype 7a strain2014In: BMC Genomics, ISSN 1471-2164, E-ISSN 1471-2164, Vol. 15, p. 742-Article in journal (Refereed)
    Abstract [en]

    Background: Shigella flexneri is the major cause of bacillary dysentery in the developing countries. The lipopolysaccharide (LPS) O-antigen of S. flexneri plays an important role in its pathogenesis and also divides S. flexneri into 19 serotypes. All the serotypes with an exception for serotype 6 share a common O-antigen backbone comprising of N-acetylglucosamine and three rhamnose residues. Different serotypes result from modification of the basic backbone conferred by phage-encoded glucosyltransferase and/or acetyltransferase genes, or plasmid-encoded phosphoethanolamine transferase. Recently, a new site for O-acetylation at positions 3 and 4 of Rha(III), in serotypes 1a, 1b, 2a, 5a and Y was shown to be mediated by the oacB gene. Additionally, this gene was shown to be carried by a transposon-like structure inserted upstream of the adrA region on the chromosome. Results: In this study, a novel bacteriophage Sf101, encoding the oacB gene was isolated and characterised from a serotype 7a strain. The complete sequence of its 38,742 bp genome encoding 66 open reading frames (orfs) was determined. Comparative analysis revealed that phage Sf101 has a mosaic genome, and most of its proteins were >90% identical to the proteins from 12 previously characterised lambdoid phages. In addition, the organisation of Sf101 genes was found to be highly similar to bacteriophage Sf6. Analysis of the Sf101 OacB identified two amino acid substitutions in the protein; however, results obtained by NMR spectroscopy confirmed that Sf101-OacB was functional. Inspection of the chromosomal integration site of Sf101 phage revealed that this phage integrates in the sbcB locus, thus unveiling a new site for integration of serotype-converting phages of S. flexneri, and determining an alternative location of oacB gene in the chromosome. Furthermore, this study identified oacB gene in several serotype 7a isolates from various regions providing evidence of O-acetyl modification in serotype 7a. Conclusions: This is the first report on the isolation of bacteriophage Sf101 which contains the S. flexneri O-antigen modification gene oacB. Sf101 has a highly mosaic genome and was found to integrate in the sbcB locus. These findings contribute an advance in our current knowledge of serotype converting phages of S. flexneri.

  • 334.
    Jalalian, Nazli
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis and applications of diaryliodonium salts2010Licentiate thesis, comprehensive summary (Other academic)
  • 335.
    Jalalian, Nazli
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ishikawa, Eloisa E.
    Silva Jr., Luiz F.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Room temperature, metal-free synthesis of diaryl ethers with use of diaryliodonium salts2011In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 13, no 6, p. 1552-1555Article in journal (Refereed)
    Abstract [en]

    A fast, high-yielding synthesis of diaryl ethers with use of mild and metal-free conditions has been developed. The scope includes bulky orthosubstituteddiaryl ethers, which are difficult to obtain by metal-catalyzed protocols. Halo-substituents, racemization-prone amino acid derivatives,and heteroaromatics are also tolerated. The methodology is expected to be of high utility in the synthesis of complex molecules and in thepharmaceutical industry.

  • 336.
    Jalalian, Nazli
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Petersen, Tue B.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Metal-Free Arylation of Oxygen Nucleophiles with Diaryliodonium Salts2012In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 18, no 44, p. 14140-14149Article in journal (Refereed)
    Abstract [en]

    Phenols and carboxylic acids are efficiently arylated with diaryliodonium salts. The reaction conditions are mild, metal free, and avoid the use of halogenated solvents, additives, and excess reagents. The products are obtained in good-to-excellent yields after short reaction times. Steric hindrance is very well tolerated, both in the nucleophile and diaryliodonium salt. The scope includes ortho-and halo-substituted products, which are difficult to obtain by metal-catalyzed protocols. Many functional groups are tolerated, including carbonyl groups, heteroatoms, and alkenes. Unsymmetric salts can be chemoselectively utilized to obtain products with hitherto unreported levels of steric congestion. The arylation has been extended to sulfonic acids, which can be converted to sulfonate esters by two different approaches. With recent advances in efficient synthetic procedures for diaryliodonium salts the reagents are now inexpensive and readily available. The iodoarene byproduct formed from the iodonium reagent can be recovered quantitatively and used to regenerate the diaryliodonium salt, which improves the atom economy.

  • 337.
    Jalilian, Ehsan
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Liao, Rong-Zhen
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Himo, Fahmi
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Brismar, Hjalmar
    Laurell, Fredrik
    Lidin, Sven
    Luminescence properties of the Cu4I62- cluster2011In: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, Vol. 13, no 14, p. 4729-4734Article in journal (Refereed)
    Abstract [en]

    Two new solvates were prepared in the system Cu(I)I using a solvolysis reaction. The structures for both of them were solved by X-ray crystllaography, showing that they constitute two modifications of the same compound with the net formula [Cu4I6](P(C6H5)4)2·2OC(CH3)2. Both types of crystals show vivid fluorescence when exposed to UV light. The formation of the first modification (I) seems to be preferred by kinetics and on ageing in the mother liquor it converts to modification (II). The Cu positions in (I) are disordered while those in (II) are fully ordered. The luminescent properties of both crystals were characterized using a confocal microscope and an excitation wavelength of 405 nm, resulting in fluorescence spectra with the intensities of 1.22 and 0.52 relative to the reference (fluorescein 10 µM). Density functional theory calculations on the ordered Cu4I62− core of modification (II) show that the de-excitation from LUMO to HOMO is responsible for the luminescence. The calculated emission spectrum has a maximum at 531 nm in good agreement with the results from confocal microscopy.

  • 338.
    Jalilian, Ehsan
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Liao, Rong-Zhen
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Himo, Fahmi
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lidin, Sven
    Luminescence properties of monoclinic Cu4I4(Piperidine)42011In: Materials research bulletin, ISSN 0025-5408, E-ISSN 1873-4227, Vol. 46, no 8, p. 1192-1196Article in journal (Refereed)
    Abstract [en]

    A new modification of Cu4I4Pip4 has been synthesized under hydrothermal conditions. X-ray crystallography revealed that this compound crystallized in the monoclinic system and consists of a tetrahedral core with composition Cu4I4, in which each Cu atom is coordinated by a piperidine molecule via the N atom. In contrast to a previously reported modification of Cu4I4Pip4, the present modification shows luminescent properties when exposed to UV-light. In addition, we have used time-dependent density functional theory calculations to characterize both compounds in term of both absorption and emission.

  • 339.
    Janson, Pär G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Metal-catalyzed oxidative formation of C-CF3 and C-O bonds in alkenes and alkynes2012Licentiate thesis, comprehensive summary (Other academic)
  • 340.
    Janson, Pär G.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ghoneim, Ibrahim
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ilchenko, Nadia O.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Electrophilic Trifluoromethylation by Copper-Catalyzed Addition of CF3-Transfer Reagents to Alkenes and Alkynes2012In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 14, no 11, p. 2882-2885Article in journal (Refereed)
    Abstract [en]

    Regio- and stereoselective Cu-catalyzed addition of the above hypervalent iodine reagent to alkynes and alkenes was achieved. In the presence of Cul, the reaction is suitable to perform trifluoromethyl-benzoyloxylation and trifluoromethyl-halogenation of alkenes and alkynes. Electron-donating substituents accelerate the process, and alkenes react faster than alkynes emphasizing the electrophilic character of the addition reaction.

  • 341.
    Janson, Pär G.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ilchenko, Nadia O.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Diez-Varga, Alberto
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Effects of B(2)pin(2) and PCy3 on copper-catalyzed trifluoromethylation of substituted alkenes and alkynes with the Togni reagent2015In: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 71, no 6, p. 922-931Article in journal (Refereed)
    Abstract [en]

    The copper-catalyzed oxytrifluoromethylation of phenylacetylenes and C-H trifluoromethylation of quinones were studied. It was found that both reactions are accelerated by B(2)pin(2) and PCy3 additives. The two reactions have different substituent effects. The oxytrifluoromethylation is faster in the presence of electron-donating groups, while the C-H trifluoromethylation is faster with electron-withdrawing substituents. The Hammett plot for oxytrifluoromethylation gave a rho value of 0.76 indicating electron demand in the rate determining step of the reaction. According to the absolute value of rho the reaction probably does not proceed through a rate determining formation of a carbocation intermediate. The kinetic isotope effect measurements indicate that in C-H trifluoromethylation of quinones the cleavage of the C-H bond is not the rate determining step of the reaction.

  • 342.
    Jansson, Jennie L. M.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Maliniak, Arnold
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Conformational Dynamics of Oligosaccharides: NMR Techniques and Computer Simulations2006In: NMR Spectroscopy and Computer Modeling of Carbohydrates: Recent Advances / [ed] Johannes F. G Vliegenthar & Robert J. Woods, American Chemical Society (ACS), 2006, p. 20-39Chapter in book (Refereed)
    Abstract [en]

    NMR spectroscopy techniques in conjunction with molecular dynamics simulations facilitate description of conformation and dynamics of oligosaccharides in solution. Herein we describe approaches based on hetero-nuclear carbon-proton spin-spin coupling constants useful for assessing conformational preferences at the glycosidic linkage, exemplified for á-cyclodextrin. Furthermore, we utilize hetero-nuclear carbon-proton residual dipolar couplings together with molecular dynamics simulations in the analysis of the conformational dynamics of the milk oligosaccharide Lacto-N-neotetraose.

  • 343.
    Jiang, Liying
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Dziedzic, Pawel
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Spacil, Zdenek
    Stockholm University, Faculty of Science, Department of Analytical Chemistry. University of Washington, USA.
    Zhao, Gui-Ling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nilsson, Lennart
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Cordova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Mid-Sweden University, Sweden.
    Abiotic synthesis of amino acids and self-crystallization under prebiotic conditions2014In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 4, article id 6769Article in journal (Refereed)
    Abstract [en]

    Building on previous research on the origin and homochirality of life, this study focuses on analyses profiling important building blocks of life: the natural amino acids. The spark discharge variation of the iconic Miller experiment was performed with a reducing gas mixture of ammonia, methane, water and hydrogen. Amino acid analysis using liquid chromatography coupled with tandem mass spectrometry after pre-column derivatizaiton revealed the generation of several amino acids including those essential for life. Re-crystallization of the synthetic products and enantiomeric ratio analysis were subsequently performed. Results from liquid chromatography coupled with either fluorescent detector or tandem mass spectrometry after pre-column derivatization with chiral reagent revealed spontaneous and effective asymmetric resolution of serine and alanine. This work describes a useful analytical platform for investigation of hypotheses regarding the origin and homochirality of amino acids under prebiotic conditions. The formation of numerous amino acids in the electric discharge experiment and the occurrence of high enantiomeric ratios of amino acids in re-crystallization experiment give valuable implications for future studies in unraveling fundamental questions regarding origins and evolution of life.

  • 344.
    Jiang, Liying
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Johnston, Eric
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åberg, K. Magnus
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Strategy for quantifying trace levels of BMAA in cyanobacteria by LC/MS/MS2013In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 405, no 4, p. 1283-1292Article in journal (Refereed)
    Abstract [en]

    The cyanobacterial neurotoxin β-N-methylamino--alanine (BMAA) is an amino acid that is putatively associated with the pathology of amyotrophic lateral sclerosis/Parkinsonism –dementia complex (ALS-PDC) disease. It raises serious health risk concerns since cyanobacteria are ubiquitous thus making human exposure almost inevitable. The identification and quantification of BMAA in cyanobacteria is challenging because it is present only in trace amounts and occurs alongside structurally similar compounds such as BMAA isomers. This work describes an enhanced liquid chromatography/tandem mass spectrometry platform that can distinguish BMAA from its isomers β-amino-N-methyl-alanine, N-(2-oethyl) glycine (AEG), and 2,4-diaminobutyric acid, thus ensuring confident identification of BMAA. The method's sensitivity was improved fourfold by a post-column addition of acetonitrile. The instrument and method limits of detection were shown to be 4.2 fmol/injection (or 0.5 g/one column) and 0.1 μg/g dry weight of cyanobacteria, respectively. The quantification method uses synthesized deuterated BMAA as an internal standard and exhibits good linearity, accuracy, and precision. Matrix effects were also investigated, revealing an ion enhancement of around 18 %. A lab-cultured cyanobacterial sample (Leptolyngbya PCC73110) was analyzed and shown to contain about 0.73 μg/g dry weight BMAA. The isomer AEG, whose chromatographic properties closely resemble those of BMAA, was also detected. These results highlight the importance of distinguishing BMAA from its isomers for reliable identification as well as providing a sensitive and accurate quantification method for measuring trace levels of BMAA in cyanobacterial samples.

  • 345.
    Jiang, Min
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium-Catalyzed Oxidative Regio- and Diastereoselective Diarylating Carbocyclization of Dienynes2013In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 19, no 21, p. 6571-6575Article in journal (Refereed)
  • 346.
    Jiang, Min
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Jiang, Tuo
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium-Catalyzed Oxidative Diarylating Carbocyclization of Enynes2012In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 14, no 13, p. 3538-3541Article in journal (Refereed)
    Abstract [en]

    A mild and efficient palladium-catalyzed oxidative diarylating carbocyclization of enynes is described. The reaction tolerates a range of functionalized arylboronic acids to give diarylated products in good yields. Control experiments suggest that the reaction starts with an arylpalladation of the alkyne, followed by carbocyclization, transmetalation, and reductive elimination to afford the diarylated product.

  • 347.
    Jiang, Tuo
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium(II)-catalyzed oxidativecarbocyclization: Functionalization with Boron-Containing Reagents2012Licentiate thesis, comprehensive summary (Other academic)
  • 348.
    Jiang, Tuo
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bartholomeyzik, Teresa
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mazuela, Javier
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Willersinn, Jochen
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium(II)/Bronsted Acid-Catalyzed Enantioselective Oxidative Carbocyclization-Borylation of Enallenes2015In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 54, no 20, p. 6024-6027Article in journal (Refereed)
    Abstract [en]

    An enantioselective oxidative carbocyclization-borylation of enallenes that is catalyzed by palladium(II) and a Bronsted acid was developed. Biphenol-type chiral phosphoric acids were superior co-catalysts for inducing the enantioselective cyclization. A number of chiral borylated carbocycles were synthesized in high enantiomeric excess.

  • 349.
    Jiang, Tuo
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Persson, Andreas K. A.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium-Catalyzed Oxidative Carbocyclization/Arylation of Enallenes2011In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 13, no 21, p. 5838-5841Article in journal (Refereed)
    Abstract [en]

    A stereoselective palladium-catalyzed oxidative carbocyclization/arylation of enallenes is described. The reaction shows wide tolerance toward highly functionalized arylboronic acids and results In a cis addition of two carbon moieties to an olefin in good to excellent yields.

  • 350.
    Jiang, Tuo
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Quan, Xu
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhu, Can
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Andersson, Pher G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium-Catalyzed Oxidative Synthesis of a-Acetoxylated Enones from Alkynes2016In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 55, no 19, p. 5824-5828Article in journal (Refereed)
    Abstract [en]

    We report a palladium-catalyzed oxidative functionalization of alkynes to generate -acetoxylated enones in one step. A range of functional groups are well-tolerated in this reaction. Mechanistic studies, including the use of O-18-labeled DMSO, revealed that the ketone oxygen atom in the product originates from DMSO.

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