Asymmetric cyclopropanation of styrene catalyzed by Cu-(chiral Schiff-base) complexes

Asymmetric cyclopropanation of olefins was carried out with chiral copper-Schiff base complexes derived from copper acetate monohydrate, substituted salicylaldehydes and a chiral amino alcohol. Substituents on salicylaldehyde framework demonstrate a significant effect on the steroselectivities. Those with electron-withdrawing properties enhance the selectivities, whereas bulky sustituents in ortho position to the phenol hydroxy group decrease the selectivities. An ee of more than 98% was achieved for the reaction of styrene with diazoacetate. (C) 2000 Elsevier Science Ltd. All rights reserved.