Asymmetric Polymerization of N-1-Anthrylmaleimide with Diethylzinc-Chiral Ligand Complexes and Optical Resolution Using the Polymer

Asymmetric anionic homopolymerizations of N-1-anthrylmaleimide (1-AMI) were performed with diethylzinc (Et2Zn)-chiral ligand complexes to obtain optically active polymers. The optical activity of poly(1-AMI) was influenced by polymerization conditions such as temperature, solvents and structures of chiral ligands. Poly(1-AMI) obtained with Et2Zn/(–)-2,2’-(1-ethylpropylidene)bis(4-benzyl-2-oxazoline) (Bnbox) in THF at 0°C showed the highest specific optical rotation ([α]D25=+92.5°). CD spectra of (+)-poly(1-AMI) exhibited negative exciton chirality around 230–300 nm, indicating that 1Bbtransition moments of anthryl groups were twisted counterclockwise. Chiral recognition ability of poly(1-AMI) was investigated by 1H NMR and HPLC, and the polymer coated on silica gel optically resolved 1, 1’-bi-2-naphthol.