Titanium-catalyzed stereoselective geminal heterodihalogenation of beta-ketoesters.
[reaction: see text] beta-Ketoesters can be effectively monofluorinated with F-TEDA using CpTiCl(3) as a catalyst. With the use of this catalyst, the extent of the competing difluorination does not reach 10%. [TiCl(2)(TADDOLato)] complexes catalyze the one-pot enantioselective heterodihalogenation of beta-ketoesters with F-TEDA and NCS to afford alpha-chloro-alpha-fluoro-beta-ketoesters in moderate to good yields. The sequence of addition of the halogenating agents determines the sense of chiral induction.
Department of Chemistry, Swiss Federal Institute of Technology, ETH Hönggerberg, CH-8093 Zürich, Switzerland.
Richard
R
Frantz
Lukas
L
Hintermann
Mauro
M
Perseghini
Diego
D
Broggini
Antonio
A
Togni