Chiral 2,2'-bipyridines, 1,10-phenanthrolines, and 2,2':6',2' '-terpyridines: syntheses and applications in asymmetric homogeneous catalysis.

Although chiral phosphines have enjoyed a longtime popularity in the design of enantioselective catalytic systems, there has been a recent renaissance in the use of nitrogen ligands for this same purpose.1 This renaissance partly arises from several distinct advantages presented by nitrogen-containing ligands. First, they can often be employed in catalytic processes where the use of phosphines may be incompatible with the reaction conditions. Second, many nitrogen ligands are now available in enantiomerically pure form. Third, ligands that bind through nitrogen are known to coordinate with a wide variety of metal ions, and considerable progress has been made in understanding the role which these ligands play in affecting catalytic processes.