Metal Bridging for Directing and Accelerating Electron Transfer as Exemplified by Harnessing the Reactivity of AIBN

A new strategy for tuning the electron transfer between radicals and enolates has been developed. This method elicits the innate reactivity of AIBN with a copper catalyst and enables a cascade reaction with cinnamic acids. Electron paramagnetic resonance studies and control experiments indicate that the redox-active copper species not only activates the radical by coordination, but also serves as a bridge to bring the radical and nucleophile within close proximity to facilitate electron transfer. By exploiting possible combinations of redox-active metals and radical entities with suitable coordinating functional groups, this strategy should contribute to the development of a broad range of radical-based reactions.