Chemoselective trifluoromethylation of the C=N group of alpha-iminoketones derived from arylglyoxals

Chemoselective addition of (trifluoromethyl)trimethylsilane to the C=N group of N-(tert-butyl)-alpha-iminoketones in the presence of a fluoride ion as a catalyst was achieved under acidic conditions. Subsequent diastereoselective reductions of the obtained alpha-amino-alpha-(trifluoromethyl)ketones led to beta-amino-beta-(trifluoromethyl) alcohols in very good yields and high diastereoselectivities. Different reducing agents were tested; the reduction performed with LiAlH4 and Raney-Ni, respectively, afforded the desired diastereoisomers in a reversed ratio