The asymmetric Heck reaction: recent developments and applications of new palladium diphenylphosphinopyrrolidine complexes

The development of the intermolecular and intramolecular asymmetric Heck reactions catalysed by palladium complexes of chiral diphosphine ligands, mainly (R)–BINAP, is reviewed. Recent developments using chiral phosphinamine ligands, including some preliminary results on the application of new diphenylphosphinopyrrolidine ligands to the intermolecular asymmetric Heck, are presented. These ligands show good regioselectivities but moderate enantioselectivities when compared to the phosphinooxazoline ligands. The latter class has extended the range of substrates to which the asymmetric Heck can be applied and exhibit better reactivities, regioselectivities and enantioselectivities when compared to (R)–BINAP. The exploitation of the intramolecular asymmetric Heck reaction in total synthesis is demonstrated through asymmetric approaches to a range of bioactive natural products. Some of the more recent mechanistic investigations of the Heck reaction are also discussed.