New Method for Asymmetric Polymerization: Asymmetric Allylic Substitution Catalyzed by a Planar-Chiral Ruthenium Complex

Abstract

A new type of asymmetric polymerization reaction by asymmetric allylic substitution catalyzed by planar-chiral cyclopentadienyl-ruthenium (Cp′Ru) complexes is described. Achiral AB-type monomers, which feature both the allylic chloride and N-alkoxyamide moieties in a single molecule, are smoothly polymerized by the catalysis of chiral ruthenium complexes with quantitative monomer conversion to afford optically active polyamides in good yields. The resulting polymers are characterized by optical rotation, circular dichroism, and 1H NMR analyses, which clearly show that the polymerization system works in a highly stereoselective manner to afford optically active polyamides with high regio- and enantioselectivities. The results revealed that the planar-chiral Cp′Ru complexes work as a highly efficient catalyst to control the stereochemistry even in the polymerization reaction.