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  • Titanium(IV)‐Catalyzed Enantioselective Sulfenylation of β‐Ketoesters.
    ChemInform, 2006
    Co-Authors: Marjan Jereb, Antonio Togni
    Abstract:

    A [Ti(TADDOLato)] complex (1) catalyzes the enantioselective sulfenylation of Beta-Ketoesters using phenylsulfenyl chloride, giving ees of up to 88% and yields of up to 95%. The reaction does not require the presence of a base. [reaction: see text]

  • Titanium(IV)-Catalyzed Enantioselective Sulfenylation of β-Ketoesters
    Organic letters, 2005
    Co-Authors: Marjan Jereb, Antonio Togni
    Abstract:

    A [Ti(TADDOLato)] complex (1) catalyzes the enantioselective sulfenylation of Beta-Ketoesters using phenylsulfenyl chloride, giving ees of up to 88% and yields of up to 95%. The reaction does not require the presence of a base. [reaction: see text]

  • expanding the scope of asymmetric electrophilic atom transfer reactions titanium and ruthenium catalyzed hydroxylation of β ketoesters
    Proceedings of the National Academy of Sciences of the United States of America, 2004
    Co-Authors: Patrick Y Toullec, Cristina Bonaccorsi, Antonio Mezzetti, Antonio Togni
    Abstract:

    The enantioselective formation of a quaternary stereogenic center coinciding with a hydroxylation process is a very rare reaction from a homogeneous catalysis point of view. Indeed, to our knowledge, no asymmetric transition-metal-catalyzed direct hydroxylation has been reported before. We describe here our initial study concerning the enantioselective alpha-hydroxylation of various Beta-Ketoesters catalyzed by Lewis-acidic complexes. Specifically, it was found that the Ti complex [TiCl(2)((R,R)-1-Np-TADDOLato)(MeCN)(2)] affords the hydroxylated products in high yield and enantioselectivities up to 94% enantiomeric excess when using 2-(phenylsulphonyl)-3-(4-nitrophenyl)oxaziridine as the oxidizing agent. Chiral enantiopure compounds of the latter type have been used previously in stoichiometric asymmetric hydroxylation reactions. We also show that, in a complementary approach with H(2)O(2) as the oxidant, the Ru(II) complex [RuCl(OE(2))((S,S)-PNNP)]PF(6) catalyzes the same type of transformation in a case of substrates showing a very substantial extent of enolization under reaction conditions; being, however, unreactive toward only weakly enolized Beta-Ketoesters.