Solubility-Equilibrium-Assisted Kinetic Resolution Polymerization toward Isotactic Polyesters Containing Axial Chirality

Abstract

High-level control over polymer stereochemistry leverages the fine-tuning of material properties, but it is still a formidable challenge in synthetic polymer chemistry. Herein we prepared a new class of salph yttrium catalysts bearing axially chiral binaphthyl moieties for axially stereocontrolled polymerization of rac-Me-DBO. (S)-Y3-bearing bulkier binaphthyl units accomplished moderate isoselectivity via kinetic resolution polymerization, affording P(Me-BDO) with a P_m of up to 0.80. Remarkably, exploiting the solubility equilibrium to maintain a constant for the concentration of two enantiopure monomer pairs in the solution state contributed to a boost in polymerization isoselectivity and furnished isotactic P(Me-DBO) products with a P_m of up to 0.93. Detailed mechanistic investigations supported our solubility-equilibrium shifting hypothesis. This solubility-equilibrium-assisted kinetic resolution polymerization strategy was expected to become a versatile platform to improve stereocontrol without de novo catalyst design.