Oxidative PCET‐Triggered Benzylic C─H Iminolactonization via 1,5‐HAT/Cyclization Enabled by Cage‐Confined Photocatalysis

ABSTRACT We present a visible‐light‐driven photocatalytic platform based on a photosensitive metal–organic cage (PMOC), which enables selective recognition and activation of amidyl N─H bonds while suppressing competing homocoupling pathways. This system promotes a controlled intramolecular 1,5‐HAT/cyclization cascade via an oxidative proton‐coupled electron transfer (PCET) process, using commercially available BPO as oxidant and the in situ generated benzoate anion as the base. Mechanistic studies reveal that the cage architecture serves a dual role—facilitating oxidative PCET and enforcing product selectivity through spatial confinement—which steers the reaction through a unimolecular pathway, effectively inhibiting N─N homodimerization typical of bulk‐phase systems. This work establishes cage‐confined photocatalysis as a powerful strategy for directing nitrogen‐centered radical (NCR) reactivity toward the synthesis of value‐added heterocyclic compounds.