New Synthetic Approach for Optically Active Polymer Bearing Chiral Cyclic Architecture: Combination of Asymmetric Allylic Amidation and Ring-Closing Metathesis Reaction

Abstract

A new synthetic approach for optically active polymer-bearing chiral cyclic architecture is described. The polymer is prepared by a combination of asymmetric allylic amidation catalyzed by planar-chiral ruthenium (Cp′Ru) complexes and ring-closing metathesis (RCM) reaction. We have designed bifunctional monomers bearing allylic chloride and N-alkoxyamide possessing an olefinic moiety, and the resulting polymer provides two olefinic moieties for RCM reactions in each monomer unit. These monomers are smoothly polymerized by Cp′Ru catalyst with quantitative conversion to afford the desired optically active polymer with high regio- and enantioselectivities. The resulting polymer is easily converted to one chiral cyclic structure (3,6-dihydro-2H-oxazine) per monomer unit via RCM catalyzed by the second-generation Hoveyda–Grubbs catalyst. Additionally, the polymerization system is applicable to various monomers, which afford optically active polymers possessing several types of main chain and side chain structures.