Systematic study of the asymmetric methoxycarbonylation of styrene catalyzed by palladium systems containing chiral ferrocenyl diphosphine ligands

We present the first systematic study of the Pd-catalyzed asymmetric methoxycarbonylation of styrene in the presence of chiral ferrocenyl phosphine ligands. The reaction conditions were optimized, and a screening of different catalyst precursors was performed. A number of 1,1'-bis(phosphino)ferrocenes of the Mandyphos, Josiphos, Walphos, and Taniaphos types were tested in combination with [PdCl2(NCPh)(2)], in the presence of TsOH as the acid source. These systems afforded high enantioselectivities, although the regioselectivity of the reaction was found to be in favor of the (undesired) linear ester. The catalytic system made with the Josiphos ligand 1 gave rise to an enantiomeric excess (ee) of 86%.