Novel C2-symmetric bisoxazolines with a chiral trans-(2 R,3 R)-diphenylcyclopropane backbone: preparation and application in several enantioselective catalytic reactions

Abstract

Various chiral bisoxazoline ligands with a chiral trans-(2 R,3 R)-diphenylcyclopropane backbone have been efficiently synthesized (five examples). These chiral ligands were tested and compared in palladium(0)-catalysed enantioselective allylic alkylations (up to 97% ee), copper(I)-catalysed enantioselective cyclopropanations (up to 89% ee) and aziridinations (up to 90% ee). We observed that the presence of a stereogenic centre on the oxazoline moiety is mandatory in order to obtain acceptable enantioselectivities.