Asymmetric anionic polymerization of N-substituted maleimides with n-butyllithium-methylene-bridged 2,2-bis(oxazoline) complexes

Asymmetric anionic homopolymerizations of achiral N-substituted maleimide (RMI: R = cyclohexyl (CHMI), R = phenyl (PhMI), R = tert-butyl (TBMI)) were carried out with n-butyllithium (n-BuLi)-chiral bis(oxazoline) complexes to obtain optically active polymers. (-)-2,2'-(1-Ethylpropylidene)bis(4-alkyl-2-oxazoline) derivatives [4-alkyl(R'): R' = benzyl ((S,S)-Bnbox), R' = isobutyl ((S,S)-i-Bubox), R' = isopropyl ((S,S)-i-Prbox), and R' = phenyl ((R,R)-Phbox))] were prepared from amino alcohols and diethylmalonic acid. The polymer initiated by n-BuLi-(S,S)-Bnbox showed the highest specific rotation (poly(CHMI), [alpha](435)(25) +111.4 degrees). The poly(TBMI) prepared with.(S,S)-i-Prbox as chiral Ligand showed a negative specific rotation (-19.1 degrees). The poly(TBMI) initiated by n-BuLi-(R,R)-Phbox showed a large specific rotation (-63.2 degrees). The specific rotations were attributed to different contents between stereogenic centers (S,S) and (R,R) based an threo-diisotactic structures of the main chain.