Palladium‐Catalyzed Carbonylative Alternating Copolymerization of Alkynols and Carbon Monoxide

ABSTRACT Conventional methods for polyester synthesis offer limited control over stereochemistry and exhibit constrained functional group tolerance, restricting access to unsaturated polymer architectures with programmable backbone dynamics and critically precluding the formation of ultra‐high‐molecular‐weight (UHMW) chains required for advanced mechanical performance. Here, we report a palladium‐catalyzed carbonylative alternating copolymerization that directly transforms readily available terminal ynols and carbon monoxide into well‐defined unsaturated polyesters. By strategically extending the ynol chain length, we suppress the entropically favored intramolecular cyclization pathway and instead promote intermolecular, enthalpy‐driven chain growth. Ligand engineering of the Pd/phosphine catalytic system achieves exceptional regioselectivity (>99%) for Markovnikov addition, producing regioregular α,β ‐unsaturated polyesters with UHMW ( M n up to 1,390 kDa) and controlled E / Z olefin ratios (up to 99:1). This alkynol‐based carbonylative polymerization establishes a versatile platform for synthesizing functional UHMW polyesters with tailored topologies, addressing long‐standing challenges in precision polyester synthesis and sustainable polymer design.