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  • 101.
    Vasse, Jean Luc
    et al.
    KTH, Superseded Departments, Chemistry.
    Stranne, Robert
    KTH, Superseded Departments, Chemistry.
    Zalubovskis, Raivis
    KTH, Superseded Departments, Chemistry.
    Gayet, Carole
    KTH, Superseded Departments, Chemistry.
    Moberg, Christina
    KTH, Superseded Departments, Chemistry.
    Influence of steric symmetry and electronic dissymmetry on the enantioselectivity in palladium-catalyzed allylic substitutions2003In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 68, no 8, p. 3258-3270Article in journal (Refereed)
    Abstract [en]

    Chiral P,N-ligands with pseudo-C2 and pseudo-Cs symmetry based on chiral pyrrolidine and phospholane rings or on dinaphthatodihydroazepino and dinaphthatodihydrophosphepino moieties were prepared and assessed in the palladium-catalyzed allylic substitutions of allylic acetates. Higher selectivity was achieved with pseudo-C2-symmetric ligands based on the binaphthyl skeleton than with the analogous C2-symmetric P,P- and N,N-analogues. Pseudo-C2-type ligands had properties superior to those of pseudo-meso-type ligands when 1,3-diphenyl-2-propenyl acetate was used as a substrate, whereas the reverse situation was found for 3-cyclohexenyl acetate. Chirally flexible ligands, prepared by substitution of one of the rigid binaphthyl skeletons for a flexible biphenyl system, were found to induce chirality to the same extent as a 1:1 mixture of the rigid ligands.

  • 102.
    Wen, Ye-Qian
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Hertzberg, Robin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Gonzalez, Inanllely
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Minor Enantiomer Recycling: Application to Enantioselective Syntheses of Beta Blockers2014In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 20, no 13, p. 3806-3812Article in journal (Refereed)
    Abstract [en]

    Continuous recycling of the minor product enantiomer obtained from the acetylcyanation of prochiral aldehydes provided access to highly enantiomerically enriched products. Cyanohydrin derivatives, which under normal conditions are obtained with modest or poor enantiomeric ratios, were formed with high enantiomeric purity by using a reinforcing combination of a chiral Lewis acid catalyst and a biocatalyst. The primarily obtained products were transformed into -adrenergic antagonists (S)-propanolol, (R)-dichloroisoproterenol, and (R)-pronethalol by means of a two-step procedure.

  • 103.
    Wen, Ye-Qian
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Hertzberg, Robin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Enantioselective Acylphosphonylation-Dual Lewis Acid-Lewis Base Activation of Aldehyde and Acylphosphonate2014In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 79, no 13, p. 6172-6178Article in journal (Refereed)
    Abstract [en]

    Acetoxyphosphonates were obtained by a one-step procedure consisting of reaction of diethyl acetylphosphonate with prochiral aldehydes in the presence of a catalytic system comprising a chiral Lewis acid, an achiral Lewis base, and a Bronstedt base. Best results were obtained using a tridentate Schiff base aluminum(III) Lewis acidic complex, 1H-1,2,3-benzotriazole, and a tertiary amine such as DBU. The target compounds were in most cases obtained in high yields, but with moderate enantiomeric ratios (up to 78:22).

  • 104.
    Wingstrand, Erica
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Fransson, Linda
    KTH, School of Biotechnology (BIO).
    Laurell, Anna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Hult, Karl
    KTH, School of Biotechnology (BIO).
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Minor enantiomer recycling: Metal catalyst, organocatalyst and biocatalyst working in concert2009In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 15, no 44, p. 12107-12113Article in journal (Refereed)
    Abstract [en]

     A minor enantiomer recycling one-pot procedure employing two reinforcing chiral catalysts has been developed. Continuous regeneration of the achiral starting material is effected via selective enzyme-catalyzed hydrolysis of the minor product enantiomer from Lewis acid-Lewis base catalyzed addition of acyl cyanides to prochiral aldehydes in a two-phase solvent system. The process provides O-acylated cyanohydrins in close to perfect enantioselectivities, higher than those obtained in the direct process, and in high yields. A combination of a (SS)salen Ti Lewis acid and Candida antarctica lipase B provides the products with R absolute configuration, whereas the opposite enantiomer is obtained from the (R,R)-salen Ti complex and Candida rugosa lipase.

  • 105.
    Wingstrand, Erica
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Li, Fei
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Lundgren, Stina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    O-Acylated Cyanohydrins: Versatile Intermediates and Products2007In: Chimica Oggi, ISSN 0392-839X, Vol. 25, no 5, p. 14-15Article in journal (Refereed)
    Abstract [en]

    Addition of ketonitriles to prochiral aromatic or aliphatic aldehydes in the presence of a catalytic system consisting of a chiral Lewis acid and an achiral Lewis base gives access to chiral enantioenriched O-acylated cyanohydrins. The products are useful for diverse potential applications.

  • 106.
    Wingstrand, Erica
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Lundgren, Stina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Hamberg, Anders
    KTH, School of Biotechnology (BIO), Biochemistry.
    Hult, Karl
    KTH, School of Biotechnology (BIO), Biochemistry.
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    655-ORGN - Synthesis of highly enantioenriched cyanohydrins by dual Lewis acid - Lewis base activation2007In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 234, p. 655-ORGN-Article in journal (Other academic)
    Abstract [en]

    Enantioenriched acylated cyanohydrins serve as versatile synthons and are themselves important synthetic targets.  By using our efficient catalytic dual Lewis acid - Lewis base activation system, a range of α-ketonitriles were added to both arom. and aliph. aldehydes affording highly enantioenriched O-acylated cyanohydrins in excellent yields.  The reactions proceeded smoothly in only one step with perfect atom economy.  Our recent results as well as the scope and limitations of the system will be presented together with mechanistic aspects.

  • 107.
    Wingstrand, Erica
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Lundgren, Stina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Penhoat, Maël
    KTH, School of Chemical Science and Engineering (CHE).
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Dual Lewis acid-Lewis base activation in enantioselective additions to aldehydes2006In: Pure and Applied Chemistry, ISSN 0033-4545, E-ISSN 1365-3075, Vol. 78, no 2, p. 409-414Article in journal (Refereed)
    Abstract [en]

    Reaction of benzaldehyde with ethyl cyanoformate in the presence of Lewis acidic Ti(IV) complexes of bispyridylamide or salen ligands and Lewis basic amines affords the O-alkoxycarbonylated cyanohydrin. In the presence of the salen-based catalytic system, acetyl cyanide can also be added to benzaldehyde, providing a highly enantioselective direct route to the O-acetylated cyanohydrin.

  • 108.
    Xiao, You-Cai
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Silaborative Carbocyclizations of 1,7-Enynes. Diastereoselective Preparation of Chromane Derivatives2016In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 18, no 2, p. 308-311Article in journal (Refereed)
    Abstract [en]

    Palladium(0)-catalyzed carbocyclization of 1,7-enynes mediated by (chlorodimethylsilyl)pinacolborane proceeds with 1,8-addition of the silicon and boron functions to give functionalized cyclohexane derivatives with boron attached to the exocyclic olefin. A variety of chromane dervatives are accessible by this method. In contrast to the analogous reactions with 1,6-enynes, the configuration of the newly formed stereogenic center is controlled by a stereogenic center present in the substrate.

  • 109.
    Zalubovskis, Raivis
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Bouet, Alexis
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Fjellander, Ester
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Constant, Samuel
    University of Geneva.
    Linder, David
    University of Geneva.
    Andreas, Fischer
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry (closed 20110630).
    Lacour, Jérôme
    University of Geneva.
    Privalov, Timofei
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Self-adaptable Catalysts: Substrate-Dependent Ligand Configuration2008In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 130, no 6, p. 1845-1855Article in journal (Refereed)
    Abstract [en]

    Pd(II) allyl and Pd(0) olefin complexes containing the configurationally labile ligand 1,2-bis-[4,5dihydro-3H-dibenzo[c-e]azepino]ethane were studied as models for intermediates in Pd-catalyzed allylic alkylations. According to NMR and DFT studies, the ligand prefers C-s conformation in both eta(3)-1,3-diphenylpropenyl and eta(3)-cyclohexenyl Pd(II) complexes, whereas in Pd(0) olefin complexes it adopts different conformations in complexes derived from the two types of allyl systems in both solution and, as verified by X-ray crystallography, in the solid state. These results demonstrate that the Pd complex is capable of adapting its structure to the reacting substrate. The different structural preferences also provide an explanation for the behavior of 1,3-diphenyl-2-propenyl acetate and 2-cyclohexenyl acetate in Pd-catalyzed allylic alkylations using pseudo-C-2 and pseudo-C-s symmetric ligands.

  • 110.
    Zalubovskis, Raivis
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Fjellander, Ester
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Szabó, Zoltán
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Stereochemical Control of Chirally Flexible Phosphepines2007In: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, Vol. 2007, no 1, p. 108-115Article in journal (Refereed)
    Abstract [en]

    The barriers to interconversion of the two enantiomeric atropisomers of 6-methoxy-6,7-dihydro-5H-dibenzo[c,e]phosphepine and that of the diastereomeric forms of 6-(-)menthoxy-6,7-dihydro-3H-dibenzo[c,e]phosphepine were determined by NMR spectroscopical methods to be 19.3 and 18.5 kcalmol(-1), respectively, at 298 K. The ratio of the atropisomers was shown to depend on the group bound to phosphorus. Only complexes with two homochiral ligands bound to the each metal center were obtained upon reaction with [Rh(COD)(2)](+) BF4-. The Rh complexes catalyzed the hydrogenation of alpha-acetamidocinnamate. The major isomer of 6-(-)-menthoxy-6,7-dihydro-5H-dibenzo[c,e]phosphepine was found to exhibit higher activity but to afford a product with lower ee than its diastereomer.

  • 111. Zalubovskis, Raivis
    et al.
    Hoermann, Esther
    Pfaltz, Andreas
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Iridium-catalyzed asymmetric hydrogenation of olefins using pyridine-phosphinites derived from the chiral pool2008In: ARKIVOC, ISSN 1424-6376, p. 58-66Article in journal (Refereed)
    Abstract [en]

    Cationic iridium complexes containing chiral pyridine-phosphinites, with their chirality derived from menthol or mandelic acid, were assessed in hydrogenations of trisubstituted non-functionalized olefins. Complexes with the new ligands showed high reactivity towards most of the olefins tested. The enantioselectivities varied with the structures of the substrate and the ligand. Best results were obtained in the hydrogenation of 3-hydroxy-2-methyl-1-phenylpropene using a ligand prepared from (-)-menthol, pyridyllithium and diphenylchlorophosphine (>99% conversion, 92% ee).

  • 112.
    Zhou, Hui
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Regio- and Stereoselective Hydrosilylation of 1,3-Enynes Catalyzed by Palladium2013In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 15, no 7, p. 1444-1447Article in journal (Refereed)
    Abstract [en]

    In the presence of Pd(0) and a phosphine, hydrosilylation of 1,3-enynes with Me2SiHCI proceeds to yield dienylsilanes with the silicon function added to the internal alkyne carbon atom and with (E)-configuration of newly formed olefinic bond. The silanols isolated after hydrolysis of the primarily obtained products serve as precursors to conjugated dienes with different substitution patterns.

  • 113.
    Zhou, Hui
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Tunable cross coupling of silanols: Selective synthesis of heavily substituted allenes and butadienes2012In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 134, no 38, p. 15992-15999Article in journal (Refereed)
    Abstract [en]

    1,3-Dienyl-2-silanols with a wide range of substitution patterns are readily obtained by palladium-catalyzed silaboration of 1,3-enynes followed by Suzuki-Miyaura cross coupling with aryl bromides. Subsequent Hiyama-Denmark cross coupling with aryl iodides provides either 1,3- or 1,2-dienes in high yields. The site selectivity can be fully controlled by the choice of activator used in the coupling reaction. In the presence of strong bases such as NaOt-Bu, KOt-Bu, and NaH, clean formation of 1,2-dienes takes place via allylic rearrangement. In contrast, stereo- and site-selective formation of tetra- and trisubstituted 1,3-dienes results from use of Ag 2O and Bu 4NF·3H 2O, respectively, as activators. Under microwave heating at 100 °C the base-mediated cross couplings are largely accelerated and are completed within one hour or less. The ratio of diastereomeric allenes varies depending on the substitution pattern of the silanol and ranges from >99:1 to 52:48.

123 101 - 113 of 113
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