BF3-Promoted Aromatic Substitution of N-Alkyl α-Trifluoromethylated Imine: Facile Synthesis of 1-Aryl-2,2,2-trifluoroethylamines

The aromatic substitution of three representative N-alkyl trifluoromethyl imines 1a–c (R: a, benzyl; b, benzhydryl; c, methyl), obtained from primary alkyl amines and trifluoroacetaldehyde ethyl hemiacetal, was used to investigate the preparation of 1-aryl-2,2,2-trifluoroethylamines. In the presence of BF3·OEt2, the reaction of imine 1 with various aromatic compounds proceeded smoothly at room temperature, giving N-alkyl-1-aryl-2,2,2-trifluoroethylamines in moderate-to-high yields. Moreover, successful regioselective removal of N-benzyl and N-benzhydryl groups was achieved by hydrolysis in hydrochloric acid or by palladium-catalyzed hydrogenolysis.