Unimolecular Anion-Binding Catalysts for Selective Ring-Opening Polymerization of O-carboxyanhydrides

Anion-binding can regulate anion transport in chloride channels through dynamic non-covalent interactions, which gives insights into the designing of new organocatalytic transformations but is surprisingly unexplored in polymerization catalysis. Herein, we describe an effective unimolecular anion-binding organocatalysis where 4-(dimethylamino)pyridine is anchored to a thiourea for ring-opening polymerization of O-carboxyanhydrides (OCAs) to furnish highly isotactic poly(phenyllactic acid) (Ph-PLA) with molecular weight (MW) up to 150.0 kDa, which well addresses the formidable challenge of synthesizing high MW stereoregular polyesters. Calculations and experimental studies indicate a dynamic cooperative anion-binding mechanism, where the dynamic anion-binding interaction of thiourea moiety to propagating species facilitates efficient chain propagation and the synergetic decarboxylation retains high selectivity for OCA ring-opening over side reactions (such as cyclization, epimerization, and transesterification).

Automated summary

The study describes an effective unimolecular anion-binding organocatalysis for ring-opening polymerization of O-carboxyanhydrides (OCAs), achieving the synthesis of highly isotactic poly(phenyllactic acid) (Ph-PLA) through a dynamic cooperative anion-binding mechanism. This approach addresses the challenge of synthesizing high molecular weight stereoregular polyesters by facilitating efficient chain propagation and maintaining high selectivity for OCA ring-opening over side reactions.