Enantioselective additions of (trifluoromethyl)trimethylsilane to α-imino ketones derived from aryl glyoxals

Chemoselective additions of (trifluoromethyl)trimethylsilane to α-imino ketones derived from aryl glyoxals in the presence of a catalytic amount of enantiomerically pure ammonium bromides, derived from Cinchona alkaloids and K2CO3 led to O-silylated β-imino alcohols. Subsequent reduction of these products with NaBH4 gave β-(N-alkyl)amino-α-trifluoromethyl alcohols for which the ee values were 30–71% under optimized conditions. Enantiomeric excesses were determined for the final products on the basis of 1H or 19F NMR spectra registered in the presence of chiral solvating agents.