Homogeneous Asymmetric Hydrogenation Using a Chiral Phosphinite Derivative of Carbohydrates as Ligand

Diphenylphosphinite derivatives of sugars were conveniently synthesized by the reaction of diphenylphosphinous chloride–triethylamine with sugar derivatives. Homogeneous asymmetric hydrogenations of several prochiral olefins, i.e., (Z)-α-acetylaminocinnamic acid, (Z)-α-benzoylaminocinnamic acid, itaconic acid, tiglic acid, and their esters, were carried out using rhodium(I) catalysts with the tervalent chiral phosphorus derivative of sugars. The highest optical yields for all the prochiral substrates investigated were obtained when di-μ-chloro-bis(cyclooctadiene)dirhodium(I) and methyl 2,3-O-isopropylidene-4-O-(diphenylphosphino)-α-l-rhamnopyranoside were used.