Metal-Free Visible-Light Excitation of TMSN₃ Enables [3 + 2] Cycloaddition of Arylidenecyclopropanes with Olefins

A visible-light photoredox [3 + 2] cycloaddition reaction of arylidenecyclopropanes with olefins was developed, employing the readily available and commercially accessible TMSN₃ as an efficient radical mediator. This method provides a convenient and efficient route to arylidenecyclopentanes from readily available starting materials, is metal-free, and features enhanced atom and step economy, excellent selectivity, extensive substrate versatility, favorable functional group compatibility, structural diversity, and mild reaction conditions, which further enable late-stage diversification. DFT calculations elucidated that this transformation entails sequential radical generation, radical addition, ring-opening, radical cyclization, and elimination steps.