Iron(III)-based metalloradical catalysis for asymmetric cyclopropanation via a stepwise radical mechanism

Autor: Lee, Wan-Chen Cindy, Wang, Duo-Sheng, Zhu, Yiling, Zhang, X. Peter
Zdroj: Nature Chemistry; 20230101, Issue: Preprints p1-12, 12p
Abstrakt: Metalloradical catalysis (MRC) exploits the metal-centred radicals present in open-shell metal complexes as one-electron catalysts for the generation of metal-stabilized organic radicals—key intermediates that control subsequent one-electron homolytic reactions. Cobalt(II) complexes of porphyrins, as stable 15e-metalloradicals with a well-defined low-spin d7configuration, have dominated the ongoing development of MRC. Here, to broaden MRC beyond the use of Co(II)-based metalloradical catalysts, we describe systematic studies that establish the operation of Fe(III)-based MRC and demonstrate an initial application for asymmetric radical transformations. Specifically, we report that five-coordinate iron(III) complexes of porphyrins with an axial ligand, which represent another family of stable 15e-metalloradicals with a d5configuration, are potent metalloradical catalysts for olefin cyclopropanation with different classes of diazo compounds via a stepwise radical mechanism. This work lays a foundation and mechanistic blueprint for future exploration of Fe(III)-based MRC towards the discovery of diverse stereoselective radical reactions.
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