Revisiting Arene C(sp 2 )−H Amidation by Intramolecular Transfer of Iridium Nitrenoids: Evidence for a Spirocyclization Pathway

Two mechanistic pathways, that is, electrocyclization and electrophilic aromatic substitution, are operative in most intramolecular C−H amination reactions proceeding by metal nitrenoid catalysis. Reported here is an alternative mechanistic scaffold leading to benzofused δ‐lactams selectively. Integrated experimental and computational analysis revealed that the reaction proceeds by a key spirocyclization step followed by a skeletal rearrangement. Based on this mechanistic insight, a new synthetic route to spirolactams has been developed.