Cyclopropanations via Heme Carbenes: Basic Mechanism and Effects of Carbene Substituent, Protein Axial Ligand, and Porphyrin Substitution

The article shows that the increasingly useful C'C functionalizations mediated by heme carbenes feature an FeII-based, nonradical, concerted nonsynchronous mechanism, with early transition state character. The effects of the carbene substituent, metal coordinating axial ligand, and porphyrin substituent on the reactivity of the heme carbenes is investigated.This study sheds new light into the mechanism of iron-porphyrin and hemoprotein-catalyzed cyclopropanation reactions and it is expected to facilitate future efforts toward sustainable carbene transfer catalysis using these systems.