The importance of complex stability for asymmetric copper-catalyzed cyclopropanations in [emim][OTf] ionic liquid: the bis(oxazoline)–azabis(oxazoline) case

Azabis(oxazoline)–Cu complexes are more stable than their analogues based on bis(oxazoline) ligands. This increased stability leads to improved recoverability (up to eight times) when these systems are used in an ionic liquid medium. The solution of the chiral catalyst can even be reused in different enantioselective cyclopropanation reactions and still lead to high enantiomeric excess (>90%).