Axially chiral phosphinamine ligands in asymmetric catalysis

One of the current approaches to prepare enantiomerically pure materials is to use catalytic quantities of chiral transition metal complexes in a homo geneous medium. The catalytic activity originates from the metal and the as ymmetry of the metal - catalysed process is induced by the chiral organic l igands attached to that metal. Commonly used donor atoms, which include pho sphorus, nitrogen, oxygen and sulfur, help to electronically tune the metal . A vast number of mono-, bi- and polydentate ligands have been successfull y applied in asymmetric catalysis. In this review, an attempt is made to sy stemise the role which bidentate, axially chiral phosphinamine ligands play in asymmetric catalysis. The ligands are classified, not by the reaction t o which their metal complexes have been applied, but by the biaryl and othe r groups present which induce chirality. These biaryl groupings include 3,5 -dihydro-4H-dinaphthazepines, 1-naphthyl-2-naphthylamines, 1,1'-biarylphosp hiteoxazolines, 1,1'-binaphthyloxazolines, isoquinolines, quinazolinones an d our work on pyrazine- and quinazoline-containing axially chiral ligands. Within this sub-classification the ligands are described, where feasible, i n the chronological order in which they were reported so that the developme nt of ligand architectural design can be more easily monitored. The asymmet ric transformations to which metal complexes of these ligands have been app lied include palladium catalysed allylic substitutions, copper catalysed 1, 4-additions to enones and rhodium catalysed hydroboration of vinylarenes. E xcellent enantioselectivities, regioselectivities and reactivities have bee n achieved in each of these processes.