Chiral boron-bridged bisoxazolines: Readily available anionic ligands for asymmetric catalysis

Abstract

Asymmetric cyclopropanation and monobenzoylation reactions of mesa diols employing borabox catalysts 1 (M = Cu) result in high enantioselectivities. The borabox ligands are anionic analogues of the bisoxazolines 2 and are readily prepared by lithiation of oxazolines and subsequent trapping with boron halides. (Chemical Equation Presented) The considerable potential of borabox ligands in asymmetric catalysis is shown. © 2005 Wiley-VCH Verlag GmbH & Co. KGaA.