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  • 1.
    Balan, Daniela
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Adolfsson, Hans
    Selective formation of α-methylene-β-amino acid derivatives through the aza version of the baylis-Hillman reaction2001In: The Journal of Organic Chemistry, Vol. 66, p. 6498-6501Article in journal (Refereed)
  • 2.
    Horváth, Attila
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-Erling
    Palladium(II)-Catalyzed SN2' Reactions of α-Allenic Acetates: Stereoconvergent Synthesis of (Z,E)-2-Bromo-1,3-dienes2001In: Journal of Organic Chemistry, Vol. 66, no 24, p. 8120-8126Article in journal (Refereed)
  • 3.
    Johansson, Tommy
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kers, Annika
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Stawinski, Jacek
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    2-Pyridylphosphonates: A New type of Modification for Nucleotide Analogues2001In: Tetrahedron Letters, ISSN 0040-4039, Vol. 42, no 11, p. 2217-2220Article in journal (Refereed)
    Abstract [en]

    Suitably protected dithymidine H-phosphonates afforded the corresponding dinucleoside 2-pyridylphosphonates upon treatment with N-methoxypyridinium tosylate in acetonitrile in the presence of 1,8-diazabicylo[5.4.0]undec-7-ene (DBU). The reaction was rapid (ca. 5 min), practically quantitative and proceeded stereospecifically, most likely with retention of configuration at the phosphorus centre.

    A simple and efficient protocol for the preparation of a new type of oligonucleotide analogue bearing a 2-pyridylphosphonate internucleotide linkage was developed

  • 4.
    Johansson, Tommy
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Stawinski, Jacek
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of Dinucleoside Pyridylphosphonates Involving Palladium(0)-catalysed Phosphorus-carbon Bond Formation as a Key Step2001In: Chemical Communications, ISSN 1359-7345, no 24, p. 2564-2565Article in journal (Refereed)
    Abstract [en]

    Dinucleoside 3-pyridylphosphonates, as well as their 2- and 4-pyridyl positional isomers, have been synthesised using a palladium(0)-catalysed cross coupling strategy

  • 5.
    Johansson, Tommy
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Stawinski, Jacek
    The Case for Configurational Stability of H-Phosphonate Diesters in the Presence of Diazabicyclo[5.4.0]undec-7-ene (DBU)2001In: Bioorganic & Medicinal Chemistry, ISSN 0968-0896, Vol. 9, no 9, p. 2315-2322Article in journal (Refereed)
    Abstract [en]

    Configurational stability of dinucleoside H-phosphonates and the stereochemical course of their sulfurisation in the presence of diazabicyclo[5.4.0]undec-7-ene (DBU) were investigated using 31P NMR spectroscopy. It was found that under the reaction conditions and irrespective of the type of protecting groups present in the nucleoside moieties, the H-phosphonate diesters investigated did not undergo any detectable epimerisation at the phosphorus centre, and their sulfurisation with elemental sulfur in the presence of DBU, proceeded stereospecifically. Thus, we could not confirm reports from another laboratory on a stereoselective course of sulfurisation of H-phosphonate diesters and the corresponding acylphosphonates in the presence of DBU.

  • 6. Löfstedt, Joakim
    et al.
    Franzén, Johan
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Carbon-Carbon Bond Formation in Regio- and Stereoselective Palladium-Catalyzed Cyclization of Allene-Substituted Conjugated Dienes2001In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 66, no 24, p. 8015-8025Article in journal (Refereed)
  • 7.
    Niclas, Solin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sanjay, Narayan
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Control of the Regioselectivity in Catalytic Transformations Involving Amphiphilic Bis-allylpalladium Intermediates: Mechanism and Synthetic Applications2001In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 66, no 5, p. 1686-1693Article in journal (Refereed)
    Abstract [en]

    Various dialkyl-substituted allyl chloride derivatives (2d−i) undergo regioselective palladium-catalyzed coupling reactions with allylstannanes (1a,b) and benzylidenemalonitrile (4), providing functionalized 1,7-octadienes in good yield. The catalytic reaction proceeds through an unsymmetrical amphiphilic bis-allylpalladium intermediate. An introductory electrophilic attack on the terminal position of the unsubstituted allyl moiety is followed by a nucleophilic attack on the alkyl-substituted allyl ligand. A theoretical analysis was performed by applying density functional theory at the B3PW91/DZ+P level to study the substituent effects on the electrophilic attack. According to the theoretical results, the high regioselectivity can be ascribed to the electronic effects of the alkyl substituents: The terminal alkyl groups destabilize the η13-bis-allylpalladium intermediate of the reaction; in addition, the alkyl substitution increases the activation barrier for the electrophilic attack.

  • 8.
    Niclas, Solin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mechanism of the η3-η1-η3 Isomerization in Allylpalladium Complexes: Solvent Coordination, Ligand, and Substituent Effects2001In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 20, p. 5464-5471Article in journal (Refereed)
    Abstract [en]

    The mechanism of the η3 → η1 → η3 isomerization of (η3-allyl)palladium complexes occurring as catalytic intermediates in important synthetic transformations has been studied by applying density functional theory at the B3PW91(DZ+P) level. It was found that under catalytic conditions, in the condensed phase, the isomerization process involves tetracoordinated (η1-allyl)palladium intermediates. In these intermediates a solvent molecule or another ancillary ligand coordinates to palladium. The stability of the (η1-allyl)palladium intermediates critically depends on the electronic effects and on the coordination ability of the solvent molecules and the ancillary ligands. The theoretical calculations indicate a dσ → π* type hyperconjugative interaction occurring in the η1-allyl moiety of the intermediary complexes. These hyperconjugative interactions influence the structure of the complexes and the activation barrier to rotation through the C1−C2 bond. Alkyl substitution of the metalated carbon leads to destabilization of the (η1-allyl)palladium complexes, which increases the activation energy of the syn/anti isomerization process. This substituent effect arises from a dual steric and electronic destabilizing interaction between the methyl substituent and the metal atom.

  • 9.
    Nilsson, Johan
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kraszewski, Adam
    Stawinski, Jacek
    Reinvestigation of the 31P NMR Evidence for the Formation of Diorganyl Phosphoropyridinium Intermediates2001In: Journal of the Chemical Society Perkin Transactions 2, ISSN 1364-5471, no 12, p. 2263-2266Article in journal (Refereed)
  • 10.
    Solin, Niclas
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Narayan, Sanjay
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium-catalyzed Tandem Bis-allylation of Isocyanates2001In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 3, no 6, p. 909-912Article in journal (Refereed)
    Abstract [en]

    A tandem bis-allylation of p-toluenesulfonyl isocyanate can be achieved by palladium-catalyzed three-component coupling reaction with allylstannanes and allyl chlorides. A high level of regioselectivity can be obtained by the appropriate choice of the allylic substituents. The reaction mechanism and the regiochemistry of the reaction can be explained by formation of an amphoteric bis-allylpalladium intermediate. This bis-allylpalladium intermediate undergoes an initial electrophilic attack on one of the allyl moieties followed by a nucleophilic attack on the other.

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