Chiral biferrocene-based bis(oxazolines): Ligands for Cu(I)-catalyzed asymmetric cyclopropanations of ene-diazoacetates

Abstract

Chiral biferrocene-based bis(oxazoline) compounds, which have both planar and central chirality, are synthesized. The Cu(I)-complexes of the bis(oxazolinyl)biferrocenes were found to be conformationally flexible and have a wide bile angle (136 degrees) by NMR and molecular modeling studies. The complexes catalyzed the intramolecular cyclopropanation reaction of ene-diazoacetates, and low to moderate enantioselectivities and decreased reactivity were observed, compared to known malonate-derived bis(oxazoline) systems. (C) 1999 Elsevier Science Ltd. All rights reserved.