Titanium-catalyzed stereoselective geminal heterodihalogenation of β-ketoesters

beta-Ketoesters can be effectively monofluorinated with F-TEDA using CpTiCl3 as a catalyst. With the use of this catalyst, the extent of the competing difluorination does not reach 10%. [TiCl2(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.