Synthesis and applications of HexaPHEMP, a novel biaryl diphosphine ligand

The novel biaryldiphosphine ligand 1 (Hexa-PHEMP) has been prepared in five steps from commercially available 3,4,5-trimethylphenol using a concise synthetic route. This approach also allows fine tuning of the ligand's stereoelectronic properties through the variation of the aromatic groups on the ligating phosphorus atoms. In certain asymmetric hydrogenation processes, catalysts containing this ligand were found to have enhanced activity and selectivity over other biaryldiphosphine-containing catalysts.