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.