Some factors affecting the catalytic efficiency in the enantioselective cyclopropanation of olefins by the use of insoluble polystyrene-bound bisoxazoline-copper(I) complex

A new insoluble polymer-bound bisoxazoline (IPB-box) was prepared by grafting a suitable chiral ligand derivative onto a commercial Merrifield resin. The material obtained by this route was employed in the asymmetric copper-catalyzed olefin cyclopropa nation, obtaining good activity and enantioselectivity values (54-84% yield, 71-93% ee) for a range of substrates. In addition, some key factors required for the development of effective IPB-box systems are discussed, including the local ligand symmetry and the influence of immobilization technique and catalyst loading. (C) 2008 Elsevier B.V. All rights reserved.