P-chiral phosphine oxide ligands for asymmetric catalysis
|Authors||Haynes, Richard K.
Au-Yeung, Terry Tin-Lok
|Source||Proceedings of Symposium on Frontiers of Chemistry - in conjunction with the Second Conference for Worldwide Chinese Young Chemists (CWCYC-2), p. 125-126|
|Summary||Asymmetric catalysis plays an enormously important role in pharmaceutical industry in providing organic starting compounds used for preparation of enantiomerically pure drugs. The most effective ligands have phosphorus atoms which are part of the chiral centre, that is the ligands are P-chiral. The classic method to prepare P-chiral phosphorus compounds relies on resolution of diastereoisomeric menthyl phosphinates, and displacement of the menthyl ligand by an organometallic nucleophile. The phosphine oxides are then reduced with silane-based and other reagents to the corresponding phosphine. Hower, complete stereoselectivity cannot be accomplished in the displacement step, and stereoselectivity is a function both of the nature of the organometallic nucleophile, and the conditions under which it is used. Because of these problems, attention has recently focussed on using P-chiral nucleophilic phosphorus equivalents in reaction with electrophiles.|
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