Ring-Opening Polymerization of α-Diazo Lactones: Access to Diazo-Containing Polyesters and Their Post-Polymerization Modifications

The properties of polyesters can be enhanced by the introduction of various functional groups, while transformations of a diazo group via a carbene intermediate provide efficient approaches for functional group introduction. We herein report the first ring-opening polymerization (ROP) of 5, 6, and 7-membered alpha-diazo lactones using t-BuOK as the initiator. The diazo groups can be well tolerated in the polymerization condition, leading to stable, diazo-containing polyesters that can be readily isolated and characterized. Post-polymerization transformations of the diazo groups, including [1,2]-hydrogen migration, Si-H insertions, and S-H insertions, further provide polyesters that are nontrivial to access. Further, the introduction of diazo groups generally increases the ring strain of lactones and alters their polymerizability, which is more pronounced for alpha-diazo gamma-butyrolactone. The ROP of alpha-diazo delta-valerolactone generates a new type of diazo-containing polyesters that can be depolymerized upon heating.