Preparation of Chiral Phosphinoferrocene Carboxamide Ligands and Their Application to Palladium-Catalyzed Asymmetric Allylic Alkylation

A series of phosphinoferrocene carboxamides bearing achiral (benzyl) and chiral [(R)- and (S)-1-phenylethyl] substituents at the amide nitrogen have been prepared from 1‘-(diphenylphosphino)ferrocenecarboxylic (Hdpf) and (Sp)-2-(diphenylphosphino)ferrocenecarboxylic ((Sp)-1) acids and tested
as ligands for enantioselective allylic alkylation of 1,3-diphenylallyl acetate with dimethyl malonate. At
room temperature, the alkylation reactions proceeded with complete conversions and ee's up to 90%, the
most efficient being the planar-only chiral ligand (Sp)-2-(diphenylphosphino)-1-(N-benzylcarbamoyl)ferrocene ((Sp)-2). The crystal structures of (Sp)-2 and the cationic (η3-allyl)palladium(II) complex [Pd(η3-1,3-Ph2C3H3){(Sp)-2-κ2O,P}]ClO4 ((Sp)-8) have been determined by single-crystal X-ray diffraction
and solution NMR data were obtained to provide an insight into the mechanism of chiral discrimination.