Dynamic Kinetic Resolution Polymerization: Synthesis of Chiral Polythioesters from Racemic Monomers

Chiral polymers are fundamentally important and interesting in nature and scientific research. For the preparation of chiral polymers, the standard kinetic resolution polymerization (KRP) of racemic monomers could only afford a 50% yield of chiral polymers with 50% unreacted monomer leftover. In this contribution, we have developed a dynamic kinetic resolution polymerization (DKRP) strategy to synthesize chiral polymers with complete conversion and improved isoselectivity from racemic monomers. A "Lewis acid/base-SalBinamAl" catalytic system was employed to achieve efficient DKRP of thiolactones with full monomer conversion and allowed access to chiral polythioesters with perfectly isotacticities (P_m up to 0.99). The formation of chiral polythioesters was confirmed by circular dichroism spectroscopy and optical rotation testing. Detailed kinetic investigation supported a DKRP mechanism. This work represented the very first example of dynamic kinetic resolution ring-opening polymerization and could provide a new conceptual strategy to guide and inspire the synthesis of chiral polymers from racemic monomers.