Distinct advantage of the in situ generation of quaternary ammonium fluorides under phase-transfer conditions toward catalytic asymmetric synthesis

[GRAPHICS] Quaternary ammonium fluorides were found to be efficiently generated in situ from the corresponding ammonium hydrogensulfates by treatment with commercially available potassium fluoride dihydrate (KF . 2H(2)O) in THF and directly used as a fluoride source for the generation of carbon nucleophiles from organosilicon compounds, This method can be successfully applied to the preparation of structurally well-defined, C-2-symmetric chiral quaternary ammonium fluorides of type 1 (X = F), thereby allowing catalytic enantioselective Mukaiyama-type aldol reactions under mild conditions.