Competing Pathways in Heme Catalyzed Oxidations With Porphyrin‐Centered Reactivity

The field of heme‐catalyzed oxidation chemistry predominantly focuses on oxidations performed by Compounds 0, I, and II. In the past 50 years, a number of alternative high‐valent iron porphyrin species have been identified wherein the porphyrin holds all the oxidative equivalents. Little is known regarding their potential to perform oxidations of small molecules nor their possible role in catalytic pathways. One avenue of particular interest to us is the use of isoporphyrins for the umpolung of chloride ( J. Am. Chem. Soc. 2012 , 134, 4469–4472; Inorg. Chem. 2022 , 61, 8105–8111; Angew. Chem. Int. Ed. 2023 , 62, e202313006). Here we have further explored the viability of such catalytic reactivity and found that chlorination yields remain rather low. One main complication with such reactivity is the presence of a competing pathway. Namely, we are able to efficiently transform 1,3,5‐trimethoxybenzene (TMB) to 2,6‐dimethoxybenzoquinone (DMBQ). The two pathways diverge at the iron(III) π‐dication, as TMB is capable of reducing the π‐dication to a radical π‐cation. We have further investigated the breadth of reactivity of the iron(III) π‐dication and provide comprehensive characterization of the radical π‐cation including UV–vis, resonance Raman, and Mössbauer spectroscopies, as well as mass spectrometry.