Enantioselective allylic substitutions catalyzed by [(hydroxyalkyl)pyridinooxazoline]- and [(alkoxyalkyl)pyridinooxazoline]palladium complexes

Highly enantioselective (up to >99% eel palladium-catalyzed substitution of rac-3-diphenyl-2-propenyl acetate with dimethyl malonate as nucleophile was achieved using 2-(1-hydroxyalkyl)-6-(4,5-dihydro-2-oxazolyl)pyridines and 2-(1-alkoxyalkyl)-6-(4,5-dihydro-2-oxazolyl)pyridines as ligands for palladium. The selectivity was found to be highly dependent on the nature of the substituents on the ligand and on the relative configuration of the two stereogenic centers present in the ligand. The results are discussed in terms of the conformation of the ligands in the intermediate pi-allylpalladium complexes.