Hydroxyphosphine and other oxygen-containing ligands

Carbohydrates are among the most widely available natural products and their use as ligand scaffolding has attracted considerable attention. Once a metal-chelating group is 

Pioneering studies by Selke and Oehme have demonstrated that monosaccharide ligand 

21 has some solubility in water and they reported its use in asymmetric hydrogenation of dehydroamino adds in water. However, without the addition of micelle-forming surfactants, Rh(I) complexes derived from 21 seem to have only limited solubility as well as moderate activity and selectivity. A study of the influence of carbohydrate-derived amphiphiles on the reduction of (Z)-acetamidocinnamic acid in water using [Rh(COD)2 IBF4 - -1BPPM catalyst shows that enantiomeric excesses (ee s) similar to or better than what is observed in MeOH can be obtained. The chiral amphiphile alone gave a small (6%), but reproducible selectivity when used with an achiral Rh catalyst. 

Uemura and RajanBabu groups independently reported the synthesis of Rh(I) complexes of 22 and its catalytic application in asymmetric hydrogenation in water. Synthesis of 

Later improvements addressing both problems of limited solubility and hydrolytic stability came with the development of water-soluble ligands having the notable DuPHOS skeleton, for which excellent enantioselectivity in ketone, olefin and imine reductions have been reported. Zhang and RajanBabu groups independently pursued the synthesis 

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