The economic use of precious chiral diphosphine ligands—DuPHOS and its rhodium(I) COD and NBD complexes

The use of cationic Rh(DuPHOS) precatalysts for asymmetric hydrogenation bearing NBD (norbornadiene) as counter ligand has significant advantages over the application of the related COD (cyclooctadiene) complexes. Liberation of the active catalysts by hydrogenation of COD requires much more time than complete asymmetric hydrogenation of a prochiral substrate proceeding in parallel. Due to this feature expensive DuPHOS ligands are wasted by more than 50%.