Abstract The copolymerization of low‐strain cyclic ethers, such as oxetane and anhydrides, still presents opportunities for improving compositional control in polymer synthesis. In this study, we report a halogen‐bond catalysis platform based on a nonsymmetric three‐center four‐electron (O···I···O +) iodine activation mode that enables highly selective and tunable copolymerization of oxetane and anhydride. This active catalytic structure mediates oxetane insertion through a dynamic equilibrium between nonsymmetric and symmetric iodine‐carboxylate complexes (O_ oxetane ···I···O_ carboxylate + versus O_ carboxylate ···I···O_ carboxylate +), thereby regulating ester and ether linkage ratio. Mechanistic study reveals that nonsymmetric iodine activation enforces near‐perfect alternating copolymer (>99 mol% selectivity in ester linkage) between oxetane and cyclic anhydrides. Notably, the catalytic system exhibits broad monomer scope, enabling the copolymerization of oxetane with a variety of cyclic anhydrides to yield structurally diverse polyesters. Furthermore, by tuning the carboxylate/I 2 ratio, systematic control over the ester‐to‐ether content in the resulting polyesters can be achieved. This work establishes halogen‐mediated nonsymmetric activation as a versatile and programmable platform for constructing composition‐defined polyesters from low‐strain cyclic ethers.
Hong et al. (Tue,) studied this question.