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  • 1.
    Ahlquist, Mårten
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Fabrizi, G
    Cacchi, S
    Norrby, Per-Ola
    Technical University of Denmark.
    Palladium(0) alkyne complexes as active species: a DFT investigation2005Inngår i: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, nr 33, s. 4196-4198Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Alkynes have been found to be excellent ligands for Pd(0); the stability of a range of alkyne-Pd(0) complexes, and their reactivity in oxidative addition, have been investigated by DFT methods.

  • 2.
    Ahlquist, Mårten
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Fabrizi, Giancarlo
    Cacchi, Sandro
    Norrby, Per-Ola
    Technical Univeristy of Denmark.
    The mechanism of the phosphine-free palladium-catalyzed hydroarylation of alkynes2006Inngår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 128, nr 39, s. 12785-12793Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The mechanism of the Pd-catalyzed hydroarylation and hydrovinylation reaction of alkynes has been studied by a combination of experimental and theoretical methods (B3LYP), with an emphasis on the phosphine-free version. The regioselectivity of the hydroarylation and hydrovinylation shows unexpected differences, which could be attributed mainly to the higher steric demand of the cyclohexenyl group as compared to the phenyl group. Hydroarylation of alpha,beta-acetylenic carbonyl substrates yields a very unusual anti-Michael selectivity, which is shown to result from reaction of the nonconjugated double bond, leaving the conjugation intact. In all cases were the regioselectivities reproduced by the calculations.

  • 3.
    Ahlquist, Mårten
    et al.
    Technical University of Denmark.
    Fristrup, P
    Tanner, David
    Technical University of Denmark.
    Norrby, Per-Ola
    Technical Univeristy of Denmark.
    Theoretical evidence for low-ligated palladium(0): [Pd-L] as the active species in oxidative addition reactions2006Inngår i: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 25, nr 8, s. 2066-2073Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The oxidative addition of PhI to Pd-O has been studied by DFT with a continuum representation of the solvent. It is shown that the preferred number of ligands on palladium is lower than would be expected from "conventional wisdom" and the 18-electron rule. The most favored oxidative addition is obtained when Pd is coordinated by only the aryl iodide and one additional ligand in a linear arrangement. The calculations indicate that p-orbitals on the central metal are not involved in bonding in any of the complexes described herein, in good agreement with classic ligand field theory and also with a recent bonding analysis by Weinhold and Landis, but in apparent violation of the 18-electron rule.

  • 4.
    Ahlquist, Mårten
    et al.
    Technical University of Denmark.
    Kozuch, S
    Shaik, S
    Tanner, David
    Technical University of Denmark.
    Norrby, Per-Ola
    Technical Univeristy of Denmark.
    On the performance of continuum solvation models for the solvation energy of small anions2006Inngår i: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 25, nr 1, s. 45-47Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The determination of continuum solvation models for the solvation energy of anions, was described. To investigate the reliability of the solvent model, a few explicit THF molecules were incorporated. A set of anions was chosen for which the experimental free energiesof solvation were available for both H 2O and DMSO solutions. A major difference between the water model and the DMSO model is that the latter systematically overestimates the free energy of solvation. The full water model in Jaguar v 4.2, including also nonelectrostatic terms, gives good correlation with experimental values for energy of solvation.

  • 5.
    Ahlquist, Mårten
    et al.
    Technical University of Denmark.
    Nielsen, T E
    Le Quement, S
    Tanner, David
    Technical University of Denmark.
    Norrby, Per-Ola
    Technical Univeristy of Denmark.
    An experimental and theoretical study of the mechanism of stannylcupration of alpha, beta-acetylenic ketones and esters2006Inngår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 12, nr 10, s. 2866-2873Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The title reaction has been investigated by experimental and computational (DFT) techniques, and subsequently compared to the corresponding carbocupration reaction, with particular emphasis oil the stereoselectivity. For stannylcupration of an ynone substrate, only the anti-addition product is observed, whereas for the corresponding ynoate substrate, the stereoselectivity can be affected by the reaction conditions: in the presence of methanol as proton donor, the initial syn-addition product can be trapped, whereas a syn/anti mixture is obtained in a non-protic solvent. This is in sharp contrast to the carbocupration of the same ynone substrate with a cyanocuprate (RCu(CN)Li), which is highly selective for syn-addition. The product selectivities can be understood from a detailed computational characterization of the reaction paths, and in particular from the relative stabilities of the vinyl cuprate and allenolate intermediates. It is suggested that the stereodetermining step is protonation of vinyl cuprate intermediates.

  • 6.
    Ahlquist, Mårten
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Norrby, Per-Ola
    Department of Chemistry, University of Gothenburg, Sweden.
    Dispersion and Back-Donation Gives Tetracoordinate [Pd(PPh3)4]2011Inngår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 50, nr 49, s. 11794-11797Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    18e R.I.P. The apparent compliance of [Pd(PPh3)4] ("tetrakis") with the 18-electron rule is not due to an electronic preference on the central metal. Pd is valence-saturated already by two ligands. Further ligand addition gives a minor energy gain, and is only possible due to strong back-bonding. Dispersion corrections are needed for properly describing the interactions between the ligands.

  • 7.
    Ahlquist, Mårten
    et al.
    Technical University of Denmark.
    Norrby, Per-Ola
    Göteborg University.
    Oxidative addition of aryl chlorides to monoligated palladium(0): A DFT-SCRF study2007Inngår i: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 26, nr 3, s. 550-553Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Oxidative addition of aryl chlorides to palladium has been investigated by hybrid density functional theory methods (B3LYP), including a continuum model describing the solvent implicitly. A series of para-substituted aryl chlorides were studied to see the influence of electronic effects on the reaction. It was found that the experimentally observed higher reactivity of the more electron deficient aryl chlorides is due to their ability to accept back-donation from Pd-0 and form reasonably strong pre-reactive complexes. This effect is less pronounced in the transition state; when it is measured from the pre-reactive complex, the barrier to oxidative addition is actually higher for the electron-deficient aryl chlorides, but the overall reaction barrier is still lower than for the electron-rich aryl chlorides.

  • 8.
    Ahlquist, Mårten S. G.
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Norrby, Per-Ola
    Department of Chemistry, University of Gothenburg, Sweden.
    Dispersion and back-donation gives tetracoordinate Pd(PPh3)(4)2012Inngår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 243Artikkel i tidsskrift (Annet vitenskapelig)
  • 9. Hansen, Anders L.
    et al.
    Ebran, Jean-Philippe
    Ahlquist, Mårten
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Norrby, Per-Ola
    Skrydstrup, Troels
    Heck coupling with nonactivated alkenyl tosylates and phosphates: Examples of effective 1,2-migrations of the alkenyl palladium(II) intermediates2006Inngår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 45, nr 20, s. 3349-3353Artikkel i tidsskrift (Fagfellevurdert)
  • 10.
    Santangelo, Ellen M.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Liblikas, Ilme
    Mudalige, Anoma
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Törnroos, Karl W.
    Norrby, Per-Ola
    Unelius, C. Rikard
    Asymmetric Synthesis of Iridoid Derivatives Using Resolved 2-Phenylindoline as a Chiral Auxiliary2008Inngår i: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, nr 35, s. 5915-5921Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An asymmetric synthetic route to cis,cis-nepetalactol (component of the sex pheromone for the hop aphid, Phorodon humuli) is presented. 2-Phenylindoline was resolved to provide a chiral auxiliary for the cycloaddition of oxocitral. The resolution was made by chromatographic separation of the diastereomers of the urea derivative made from 2-phenylindoline and with (R)-(+)-alpha-methylbenzyl isocyanate, followed by reductive cleavage of the isolated diasteromers using diborane. The cycloaddition of oxocitral using (S)-2-phenylindoline yielded an enantiopure product after chromatography. Hydrolysis of the cycloaddition adduct yielded gastrolactol (3). As gastrolactol is a versatile synthon for the synthesis of iridoids, the overall procedure provides a general asymmetric route to elaborated iridoids.

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