Asymmetric Strecker Reaction of Di- and Trifluoromethyl Ketoimines

Significance

The enantioselective Strecker reaction of difluoromethyl or trifluoromethyl ketoimines was reported using a quinidine-derived bifunctional urea 1 as a catalyst to synthesize α-tetrasubstituted α-aminonitriles with a α-di- or -trifluoromethyl group. A similar thiourea-catalyzed Strecker re­action has already been reported by Enders and co-workers (Adv. Synth. Catal. 2010, 352, 3147) for the α-CF₃-ketoimines, but the reaction time was long (5-22 d). In this article, the authors showed that good enantioselectivity could be obtained without additives, but the use of hexafluo­roisopropanol permitted an acceleration of the ­reaction. The authors proved the utility of the enantioenriched α-CF₂H or -CF₃ α-tetrasubstituted α-aminonitrile by synthesizing an α-CF₂H C^α-tetrasubstituted amino acid and a trifluoromethylated imidazolidinone without lost of enantioselectivity.