Enantioselective cyanosilylation of aldehydes catalyzed by novel camphor derived Schiff bases-titanium(IV) complexes

Five tridentate Schiff bases have been prepared from (1R,2S,3R,4S)-3-amino-1,7,7-trimethylbicyclo2.2.1]heptan-2-ol and salicylaldehydes. X-ray structure investigation revealed differences in their molecular conformation, and their titanium(IV) complexes have been studied with NMR techniques. Among them the complex with the Schiff base obtained from 2-hydroxy-3-isopropylbenzaldehyde, is the most selective catalyst for the cyanosilylation of aliphatic, alicyclic, aromatic, and heteroaromatic aldehydes. The highest enantioselectivity, >99%, was achieved for the addition of trimethylsilyl cyanide to cinnamaldehyde.