Synthesis of chiral bis(oxazolinyl)biferrocene ligands and their application to Cu(I)-catalyzed asymmetric cyclopropanation

Abstract

Homochiral bis(oxazolinyl)biferrocene ligands, which have both planar and central chirality, are synthesized from oxazolinylfenocenes through a diastereoselective directed lithiation followed by an oxidative dimerization. Asymmetric cyclopropanation of styrene with diazoacetates in the presence of 5 mol% CuOTf-bis(oxazolinyl)biferrocene complexes gives 2-(phenyl)cyclopropane carboxylates in up to 99% ee. (C) 1997 Elsevier Science Ltd.