Enantioselective Alternating Copolymerization of α-Olefins with Carbon Monoxide Using a Cationic Palladium−Chiral Diphosphine Complex

Abstract

Enantioselective alternating copolymerization of carbon monoxide with propylene, 1-heptene, 1-octene, and styrene was carried out using a palladium catalyst modified by 1,4−3,6-dianhydro-2,5-dideoxy-2,5-bis(diphenylphosphino)-l-iditol (DDPPI). The chiral diphosphine was proved to be effective for enantioselective copolymerization. The pure poly(1,4-ketone)s were obtained by dissolving the copolymers containing spiroketal and 1,4-ketone units in 1,1,1,3,3,3-hexafluoro-2-propanol and reprecipitating with methanol. Optical rotation, elemental analysis, and 1H NMR, 13C NMR, and IR spectra showed that our copolymers were optically active, isotactic, alternating poly(1,4-ketone) structures. An oxidant and a weakly or noncoordinating anion were important in the copolymerization.