Gradient isoselective ring-opening polymerization of racemic cyclic diolide driven by chiral phosphoric acid catalysis

Abstract

Organocatalysis has recently emerged as a powerful synthetic tool for driving ring-opening polymerization (ROP). However, it is still underexplored when involving stereocontrolled ROP. Herein, we have reported that commercially available binaphthol (BINOL)-derived chiral phosphoric acid (CPA) organocatalysts allowed for chemo- and stereoselective ROP of racemic eight-membered cyclic diolide (rac-DL), yielding gradient isotactic multiblock poly(3-hydroxybutyrate) (P3HB). Experimental and computational analysis shed light on the trade-off between kinetics and thermodynamics, leading to a combination of enantiomorphic-site and chain-end control mechanisms that appeared to be responsible for the gradient isoselectivity.