Enantioselective alpha-sulfenylation of alpha-fluoro-beta-ketoesters 4 with phenylsulfenyl chloride catalyzed by DBFOX-Ph/Ni(II) complex afforded the corresponding alpha-fluoro-alpha-sulfenyl-beta-ketoesters 2 in moderate to good yields with excellent enantiomeric excesses up to 93% ee. alpha-Fluoro-alpha-sulfenyl-beta-ketoesters can be effectively converted to tri-fluorinated alpha-sulfenylcarboxylates by the use of DAST, which should be useful intermediates for the synthesis of non-racemized fluorinated isosteres of pharmaceutically attractive SM32. The enantioselective alpha-phenylsulfenylation as well as alpha-pentafluoro-phenylsulfenylation of non-fluorinated beta-ketoesters 5 were also carried out under the same catalyst conditions affording up to 95% ee of the products 6-8. (C) 2009 Elsevier B.V. All rights reserved.
Titanium(IV)-Catalyzed Enantioselective Sulfenylation of β-Ketoesters
作者:Marjan Jereb、Antonio Togni
DOI:10.1021/ol051564g
日期:2005.9.1
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.
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