Revisiting Arene C(sp2 )-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.