Mechanistic Insights into Iron-Catalyzed C–H Bond Activation and C–C Coupling
Samantha M. Brewer, Timothy M. Schwartz, Magy A. Mekhail, Lara S. Turan, Timothy J. Prior, Timothy J. Hubin, Benjamin G. Janesko, Kayla N. Green
Abstract
Iron-catalyzed C–C coupling reactions of pyrrole provide a unique alternative to the traditional Pd-catalyzed counterpart. However, many details regarding the actual mechanism remain unknown. A series of macrocyclic iron(III) complexes were used to evaluate specifics related to the role of O2, radicals, and μ-oxodiiron-complex participation in the catalytic cycle. It was determined that the mononuclear tetra-azamacrocyclic complex is a true catalyst and not a stoichiometric reagent, while more than one equivalent of a sacrificial oxidant is needed. Furthermore, the reaction does not proceed through an organic radical pathway. μ-Oxodiiron complexes are not involved in the main catalytic pathway, and the dimers are, in fact, off-cycle species that decrease catalytic efficiency.