Asymmetric trifluoromethylation of aldehydes and ketones with trifluoromethyltrimethylsilane catalyzed by chiral quaternary ammonium fluorides

Organocatalytic Enantioselective Protonation of Silyl Enolates Mediated by Cinchona Alkaloids and a Latent Source of HF

“…[4] Quaternary cinchonium fluoride and hydrogen difluoride salts were previously reported to be catalysts for a variety of asymmetric addition reactions of silicon-based nucleophiles. [5][6][7][8] Accordingly, the use of the hydrogen fluoride salts (1-HF) of cinchona alkaloids seems to be a very simple and attractive chiral source of protons for the enantioselective protonation of silyl enolates. By taking advantage of the high affinity of silicon for the fluoride anion, we anticipated that such salts would be very active chiral sources of protons, with the resultant specific enolate-activation mode being expected to confine the proton source and C-protonation site of the silyl enolate 2 in proximity.…”

How to Reach Stereogenic Trifluoromethylated Carbon? En Route to the “Grail” of the Asymmetric Trifluoromethylation Reaction

“…[23] Nevertheless, some attempts at diastereoselective trifluoromethylation have already been realized with chiral nucleophilic molecules [24] or by adding chiral Lewis acids to prochiral compounds (Scheme 8). [25] For the moment, these preliminary results are still modest.…”

“…The first enantioselective trifluoromethylation reaction with CF 3 SiMe 3 was published in 1994. [24] The chirality is brought about from a fluoride anion associated to a chiral cation, namely a cinchonium derivative ( Table 1). The hypothesis is based on the fact that the chiral ammonium salt should be closely associated with the pentacoordinate species arising from CF 3 SiMe 3 and that it is this close coordination that would induce the enantioselectivity.…”

Development of Catalytic Asymmetric Reactions Focussing on Fluoroorganic Compounds.

“…Chiral pseudo C2-symmetric formamides. ( 19 ) the corresponding (R)-enriched alcohol 38 of 68% ee in 81% yield (entry 1). However, a decrease in the amount of 37 drastically suppressed the chemical and optical yields (entries 2-4).…”