Diazoacetates as Terminating Agents in Living Ring-Opening Metathesis Polymerization: Synthesis of Chain-End-Functionalized Polymers

We report herein a simple, efficient strategy to access diverse end-functionalized polymers from a living ring-opening metathesis polymerization process using diazoacetates as a new terminating agent. Such a terminating process occurs via a C═C bond-forming reaction between the chain-end ruthenium carbenes and the diazoacetates, resulting in the rapid construction of a unique, α,β-unsaturated carbonyl motif at more than 95% of the chain end within 5 min. A variety of easily accessible and diversely substituted diazoacetates could be used, allowing for the facile introduction of an additional panel of useful functionalities at the polymer chain end. Diverse postpolymerization modifications, including Michael addition, "click" reaction, and chain extension, have been further demonstrated.