Enantioselective cyclopropanation reactions promoted by immobilized bis(oxazoline)-copper complexes

Bis(oxazoline)-copper complexes can be immobilized by cationic exchange or a covalent bond to the support. In the first strategy the co-ordination pro perties of the solid counterion influence the results obtained, as is the c ase in the homogeneous phase. However, the solid counterions also lead to s teric interactions with the chiral ligand and so the bis(oxazoline) behaves differently depending on its substituents and the nature of the anionic su pport. The best overall results are obtained with nanocomposite Nafion-sili ca as a support and the bis(oxazoline) with phenyl groups. In the second st rategy the covalent bond between the ligand and an organic support can be a chieved using a preformed polymer or by synthesis of the support using a fu nctionalized chiral ligand. The best results are obtained with the latter s ystem but the copolymerization conditions are critical for the activity and enantioselectivity of the catalyst.