“Noninnate” Ring‐Opening Polymerization: Palladium‐Catalyzed Stereoselective 1,4‐Polymerization of Alkynylcyclopropanes

Abstract In ring‐opening polymerization (ROP), main‐chain connectivity is largely dictated by the inherent electronic and steric properties of the monomer. As a result, even when different polymerization mechanisms are employed, the same backbone structure is obtained. Here, we report catalyst‐controlled, noninnate connectivity in the ROP of alkynylcyclopropane dicarboxylates (ACPs). Leveraging π‐propargyl palladium intermediates, we redirect the reactivity from the electronically favored 1,5‐addition to a noninnate 1,4‐addition pathway, furnishing a conjugated diene‐based backbone with high regio‐ and stereoselectivity. The polymerization exhibits controlled characteristics under optimized conditions. Combined experimental and computational studies reveal that a strategically positioned quaternary carbon center enforces high configurational rigidity in the organopalladium intermediate, thereby suppressing undesired cyclization and enabling rapid, stereospecific β‐hydride elimination. This work demonstrates overriding the innate connectivity in ROP by precisely controlling the fate of organometallic intermediates.