Asymmetric chelating diphosphine

More successful attempts at asymmetric hydroformylation have involved rhodium and platinum complexes. As in asymmetric hydrogenation, best results have been obtained with optically active chelating diphosphines as ligands, but some studies of monophosphines have been made. Using... 

Water-soluble chelating diphosphines. This amine hydrochloride has been used to prepare water-soluble ligands for transition metals, particularly Rh(I). Thus, the complex Rh(I) -2 is a highly active catalyst for homogeneous hydrogenation, and Rh(I)-3 combines with the glycoprotein avidin to form an effective asymmetric catalyst lor hydrogenation of -acetamidoacrylic acid. 

Introduction. DIOP was the first example of a C2 chelating diphosphine for transition metal complexes to be used in asymmetric catalysis. It was also one of the first examples of a useful C2 chiral auxiliary. DIOP can be considered as an example of the first generation of chelating diphosphine ligands with a chiral carbon skeleton, which were followed over the next 20 years by many examples of chelating diphosphines, one of the most efficient of which is BINAP [2,2 -Bis(diphenylphosphino)-l,l -binaphthyl] The ready availability of DIOP has stimulated research in asymmetric catalysis beyond the area of asymmetric hydrogenation. 

A new family of chelating diphosphines, where phosphorus is part of a five-membered ring containing two asymmetric centers, was developed at Du Pont by Burk et al. in 1990 [58a]. These C2-symmetric Hgands (duphos and derivatives) gave excellent rhodium catalysts for asymmetric hydrogenation of many types of imsatuxated systems. 

Precise steric control of the environment about an Rh center may be exerted by bulky chelating diphosphine ligands, allowing asymmetric hydrogenation to occur (see... 

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