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  • 1.
    Belda de Lama, Oscar
    KTH, Superseded Departments, Chemistry.
    Bispyridylamides as ligands in asymmetric catalysis2004Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis deals with the preparation and use of chiralbispyridylamides as ligands in metal-catalyzed asymmetricreactions.

    The compounds were prepared by amide formation usingdifferent coupling reagents. Bispyridylamides havingsubstituents in the 4- or 6- positions of the pyridine ringswere prepared by functional group interconversion of the 4- or6- halopyridine derivatives. These synthetic approaches provedto be useful for various types of chiral backbones. Pseudo C2-symmetric bispyridylamides were also synthesizedby means of stepwise amide formation.

    The compounds were used as ligands in themicrowave-accelerated Mocatalyzed asymmetric allylic alkylationreaction. Ligands having ð-donating substituents in the4-positions of the pyridine rings gave rise to products withhigher branched to linear ratio. The catalytic reaction, whichproved to be rather general for allylic carbonates with anaromatic substituent, was used as the key step in thepreparation of (R)-baclofen. The Mo-bispyridylamide catalystprecursor was studied by NMR spectroscopy.

    Bispyridylamide complexes of metal alkoxides were alsoevaluated in the asymmetric addition of cyanide to aldehydesand the metal complexes involved were studied by NMRspectroscopy and X-ray crystallography. Chiral diamines wereused as additives to study the ring opening of cyclohexeneoxide with azide, catalyzed by Zr(IV)-bispyridylamidecomplexes.

    Various bispyridylamides were attached to solid supports oforganic or inorganic nature. The solid-supported ligands wereused in Mo-catalyzed asymmetric allylic alkylation reactionsand in the asymmetric addition of cyanide to benzaldehyde.

    Keywords:asymmetric catalysis, chiral ligand, pyridine,amide, allylic alkylation, enantioselective, cyanation,ring-opening, chiral Lewis acid.

  • 2.
    Belda, Oscar
    et al.
    KTH, Superseded Departments, Chemistry.
    Duquesne, Sophie
    KTH, Superseded Departments, Chemistry.
    Fischer, A.
    Moberg, Christina
    KTH, Superseded Departments, Chemistry.
    Chiral bispyridylamide metal complexes as catalysts for the enantioselective adddition of TMSCN to aldehydes2004In: Journal of Organometallic Chemistry, ISSN 0022-328X, E-ISSN 1872-8561, Vol. 689, no 23, p. 3750-3755Article in journal (Refereed)
    Abstract [en]

    The use of (1R,2R)-N,N'-bis(2-pyridinecarboxyamido)-1,2-diphenylethane metal complexes as catalysts for the enantioselective addition of trimethylsilyl cyanide to aldehydes is described. Enantioselectivities up to 70% ee were obtained with a Ti(IV) catalyst. Complexes with Zr(IV), Sc(III), Yb(III) and Cu(II) afforded less selective catalysts. For the Zr(IV) complex, a rate and selectivity enhancement was observed when adding 0.5 equiv. of water with respect to the catalyst. Studies of the metal complexes involved in the reaction were carried out by means of H-1 NMR spectroscopy. A Zr complex was shown by X-ray crystallography to exhibit distorted octahedral coordination, with the four nitrogen atoms of the doubly deprotonated ligand essentially in one plane.

  • 3.
    Belda, Oscar
    et al.
    KTH, Superseded Departments, Chemistry.
    Moberg, Christina
    KTH, Superseded Departments, Chemistry.
    Molybdenum-catalyzed asymmetric allylic alkylations2004In: Accounts of Chemical Research, ISSN 0001-4842, E-ISSN 1520-4898, Vol. 37, no 3, p. 159-167Article in journal (Refereed)
    Abstract [en]

    The highly regio- and enantioselective molybdenum-catalyzed allylic alkylation reaction has become a powerful synthetic tool during the past few years. This Account describes the achievements gained so far in the area, with special attention directed to the different chiral ligands that have been used for inducing chirality in the products, the range of allylic substrates and nucleophiles employed, mechanistic studies, and applications of the reaction in asymmetric syntheses.

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