DIOP for Asymmetric Hydrogenation Catalysis

DIOP (Product No. 237655; [(-)-2,3-O-Isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane]) is a C₂ chelating diphosphine ligand for transition metal complexes during asymmetric catalysis and is one of the first chiral ligands used for asymmetric hydrogenation catalysis. DIOP can be synthesized in four simple steps from tartaric acid. Chelation with a rhodium complex generates an optically active catalyst active in hydrogenation. To demonstrate the activity of DIOP, Kagan and Dang conducted the asymmetric hydrogenation of a variety of alkenes.¹ Optical yields of up to 72% were obtained with substrate to catalyst ratio of up to 200:1 (Scheme 1).