Chiral ion pairs in catalysis: lithium salts of chiral metallocomplex anions as catalysts for asymmetric C-C bond formation

A series of Co(III) anionic complexes of Schiff bases obtained from substituted salicylaldehydes and optically active amino acids has been synthesized. The ion pairing of these anions to a lithium cation can be used to induce asymmetry into lithium-catalyzed trimethylsilylcyanation of aldehydes and Michael reactions. The influence of the temperature. solvent polarity and structural modification of the chiral anion on the enantioselectivity of the catalysis has been investigated. (c) 2009 Elsevier Ltd. All rights reserved.