THE ASYMMETRIC HECK REACTION - RECENT DEVELOPMENTS AND APPLICATIONS OF NEW PALLADIUM DIPHENYLPHOSPHINOPYRROLIDINE COMPLEXES

The development of the intermolecular and intramolecular asymmetric He ck reactions catalysed by palladium complexes of chiral diphosphine li gands, mainly (R)-BINAP, is reviewed. Recent developments using chiral phosphinamine ligands, including some preliminary results on the appl ication of new diphenylphosphinopyrrolidine ligands to the intermolecu lar asymmetric Heck, are presented. These ligands show good regioselec tivities but moderate enantioselectivities when compared to the phosph inooxazoline ligands. The latter class has extended the range of subst rates to which the asymmetric Heck can be applied and exhibit better r eactivities, regioselectivities and enantioselectivities when compared to (R)-BINAP. The exploitation of the intramolecular asymmetric Heck reaction in total synthesis is demonstrated through asymmetric approac hes to a range of bioactive natural products. Some of the more recent mechanistic investigations of the Heck reaction are also discussed.