Chiral P,N,N-Ligands for Asymmetric Hydrogenation

The chiral P,N,N-ligands represented a new type of tridentate ligand developed in recent years and displayed wide utilities in asymmetric catalysis. In the past decades, numerous chiral P,N,N-ligands with ferrocene, phenethylamine and spiro backbones were synthesized by addition of an aminopyridine, imidazole or diamines coordinating group. These chiral tridentate P,N,N-ligands showed excellent performance in the ruthenium, iridium, manganese, or cobalt-catalyzed asymmetric hydrogenations. A wide range of substrates, including simple ketones, alpha-halogenated ketones, alpha-hydroxy ketones, alpha- or beta-amino keto- ones, alpha-, gamma-, or delta-keto acids, alpha- or beta-keto amides, beta- or delta-keto esters, alpha- or beta-enones, olefins, imines, quinolines and indoles, could be hydrogenated to afford the corresponding chiral products with high yields and enantioselectivities. In this review, progress on the asymmetric hydrogenation of C=O, C=N, C=C bonds with chiral tridentate P,N,N-ligands was summarized. image