Asymmetric polymerization of triphenylmethyl methacrylate by C2‐chiral catalysts

Abstract

AbstractAsymmetric polymerization of triphenylmethyl methacrylate (TrMA) was investigated with optically active anionic catalysts in toluene at −78°C. The catalysts were prepared in various combinations of organolithium compounds with C2‐chiral tertiary diamines (1–6). Tetramethyl‐ethylenediamine derivative bearing an axially dissymmetric biphenyl moiety (1) and the binaphthyl analogue (4) were found to provide efficient catalysts for the preparation of highly isotactic poly(TrMA)s of very large optical rotations whose signs depended on the configurations of the diamines. Especially, the catalysts consisting of 1 gave nearly pure one‐handed helical polymers soluble in tetrahydrofuran (THF) in excellent yields, regardless of the kind of the lithium compounds used. The BuLi‐1 catalyst caused the metallation of toluene used as the solvent, and hence the resulting polymer had a benzyl moiety as an initiator fragment. The polymerization was also discussed with respect to the mole ratio of 1 to BuLi. Circular dichroism (CD) spectra of the (−)‐ and (+)‐polymers, which were obtained with the BuLi‐(R)‐1 and ‐(S)‐1 catalysts, respectively, were virtually complete mirror images of each other. High performance liquid chromatography (HPLC) using the THF–soluble, optically active poly(TrMA) as chiral adsorbent realized the complete resolution of racemic compounds.