Supported heteropolyanions as solid counterions for the electrostatic immobilization of chiral copper complexes

Supported (PW12O403-) is a suitable counterion to immobilize chiral azabis(oxazoline)-copper complexes through electrostatic interactions (ion pair formation). Catalytic results are good to excellent in cyclopropanation reactions (up to 97% ee). Partial leaching during recycling when mono-exchanged species are present, favored by strong coordination of by-products, can be minimized by a proper solvent choice and by optimization of the recycling system, allowing the recovery and reuse of the catalyst at least six times without loss of activity and enantioselectivities in the range of 82-96% ee for trans-cyclopropanes. (C) 2010 Elsevier Inc. All rights reserved.