Chemoselective trifluoromethylation of the CN group of α-iminoketones derived from arylglyoxals

• A protocol for chemoselective additon of CF3SiMe3 onto the CN bond in α-iminoketones derived from arylgyloxal was elaborated.
• The best results were achieved starting with N-t-Bu derivatives.
• α-Amino-α-trifluoromethyl ketones were reduced diastereoselectively to corresponding β-amino-β-trifluoromethyl alcohols.
• The configuration of the major product depends on the type of reducing agent (LiAlH4 versus Raney-Ni).

Chemoselective addition of (trifluoromethyl)trimethylsilane to the CN group of N-(tert-butyl)-α-iminoketones in the presence of a fluoride ion as a catalyst was achieved under acidic conditions. Subsequent diastereoselective reductions of the obtained α-amino-α-(trifluoromethyl)ketones led to β-amino-β-(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.

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