Highly Robust Iron Catalyst System for Intramolecular C(sp3)−H Amidation Leading to γ‐Lactams

Abstract Disclosed here is the use of an iron catalyst system for an intramolecular C−H amidation toward γ‐lactam synthesis from dioxazolone precursors. (Phthalocyanine)Fe III Cl was found to catalyze this cyclization with extremely high turnover numbers of up to 47 000 under mild and aerobic conditions. On the basis of experimental and computational mechanistic studies, the reaction is suggested to proceed by a stepwise radical pathway involving fast hydrogen atom abstraction followed by radical rebound. A plausible origin for the high turnover numbers along with air‐compatibility is also rationalized.