Design of chiral ligands for asymmetric catalysis: From C-2-symmetric semicorrins and bisoxazolines to non-symmetric phosphinooxazolines

Chiral C-2-symmetric semicorrins have proved to be highly efficient ligands for Cu-catalyzed enantioselective cyclopropanation of olefins and Co-catalyzed enantioselective reduction of alpha,beta-unsaturated carboxylic esters and amides. Based on these findings, analogous, readily accessible C-2-symmetric bisoxazolines have been developed which, in a short time, have become standard ligands in asymmetric catalysis, allowing effective enantiocontrol in a variety of metal-catalyzed reactions. More recently, our work has led us from C-2-symmetric nitrogen ligands to unsymmetric phosphinooxazolines. P,N-ligands of this type have been successfully applied in palladium- and tungsten-catalyzed allylic substitutions and in enantioselective Heck reactions of alkenyl and aryl triflates with cyclic olefins.