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).