Abstract
Asymmetric syntheses of cyanohydrins and aminonitriles were carried out by using chiral ligand 16/Ti(IV) complex at low temperature. Camphor based ligand 16 was prepared from Ketopinic acid chloride with optically pure (R,R)-diphenylethylene diamine, followed by stereoselective reduction with L-Selectride® in 2 steps. Ligand 16 was stable under acidic and basic conditions, and was easily recovered by recrystallization. In asymmetric synthesis of cyanohydrins, the active catalyst was prepared from 16.5mol% of chiral ligand 16 and 15 mol% of Ti(OiPr)4 in the presence of molecular sieve 4Å in nonpolar solvent . Both aromatic and aliphatic cyanohydrins were produced in modest yield with excellent enantioselectivity (95~99% e.e.) at -78℃. In addition, Asymmetric Strecker type synthesis has been tested in the same fashion as above. Unfortunately, the 16/Ti(IV) that has been successfully applied to the catalytic asymmetric synthesis of cyanohydrins was not suitable for the catalytic asymmetric synthesis ofα-aminonitriles.