Chiral Bidentate Heterodonor P-N-Other-Ligands

Abstract

Phosphorus-nitrogen ligands are key fragments in homogeneous asymmetric catalysis. In this family of ligands, those with an oxazoline ring as N-donor constitute the largest subgroup. Nevertheless, a wide array of heterodonor bidentate ligands, containing nitrogenated motifs other than oxazolines (so-called “P-N-other-ligands”), have been reported to achieve remarkable results in asymmetric catalytic transformations. The present chapter reviews the relationship between the architectural design of P-N-other-ligands and its performance in asymmetric catalysis. We will focus on recent reports but providing a quick overview of previous work in the field. In order to shed light on the structure-performance relationship of the P-N-other-ligands, we have classified them according to the nature of their N-donor atom, rather than by reaction type or metal coordination: a) group 1: amino N-donors (N-sp3); b) group 2: imino N-donors (N-sp2); c) group 3: cyclic imino N-donors (N-sp2) and d) group 4: pyridino N-donors (N-sp2). Regarding their catalytic performance, asymmetric hydrogenation and asymmetric allylic substitution reactions are the most common applications of this type of ligands. Nevertheless, they have also shown excellent results in other asymmetric transformations, such as 1,4-conjugate additions or A3 couplings.