Addition of Me3SiCN to trifluoromethyl derivates of N-(pyridylmethylidene)anilines catalyzed by Lewis acids

A series of novel Shiff bases (1a-h) was synthesized by condensation of pyr idinecarboxaldehydes (1-4) with 3- and 4-trifluoromethylanilines (5, 6) in the presence of molecular sieves (4 Angstrom). It was found that AlCl3 and AlBr3 catalyzed the addition of Me3SiCN to the C=N bond of the imines obtai ned, whereas the other Lewis acids studied (YCl3, LaCl3, ZnI2) were not act ive. The reactivity of the imines in the title reaction, on the whole, corr elated with their basicity. Besides the addition giving the expected alpha -amino nitriles (2a,b,d-f,h), an unusual reaction leading to unsaturated ni triles (3a-h) was observed. The structures of saturated and unsaturated pro ducts 2d and 3c were determined by X-ray diffraction. Copyright (C) 2001 Jo hn Wiley & Sons, Ltd.