Welches Oxidationsmittel ist wirklich verantwortlich für Oxygenierungen an P450‐Modellsystemen? – Eine kinetische Betrachtung

Franke, Alicja; Fertinger, Christoph; Eldik, Rudi van

doi:10.1002/ange.200800907

Cited by 15 publications

(9 citation statements)

References 23 publications

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“…Oxidation of [Fe III (TMP)] by m ‐CPBA in acetonitrile : As reported previously,13 the addition of a subequivalent amount of m ‐CPBA to a solution of the water‐insoluble [Fe III (TMP)] in acetonitrile at −15 °C results in the formation of the relatively stable acylperoxo iron(III)–porphyrin intermediate [(TMP)Fe III OOC(O)Ar]. The use of only a small excess of oxidant accelerates the heterolytic OO bond cleavage in [(TMP)Fe III OOC(O)Ar] and leads to the formation of the oxoiron(IV)–porphyrin cation radical [(TMP + .…”

Section: Resultssupporting

confidence: 60%

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Factors That Affect the Nature of the Final Oxidation Products in “Peroxo‐Shunt” Reactions of Iron–Porphyrin Complexes

Franke

Wolak

Eldik

2009

Chemistry A European J

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The present study focuses on the oxidation of the water-soluble and water-insoluble iron(III)-porphyrin complexes [Fe(III)(TMPS)] and [Fe(III)(TMP)] (TMPS = meso-tetrakis(2,4,6-trimethyl-3-sulfonatophenyl)porphyrinato, TMP = meso-tetrakis(2,4,6-trimethylphenyl)porphyrinato), respectively, by meta-chloroperoxybenzoic acid (m-CPBA) in aqueous methanol and aqueous acetonitrile solutions of varying acidity. With the application of a low-temperature rapid-scan UV/Vis spectroscopic technique, the complete spectral changes that accompany the formation and decomposition of the primary product of O-O bond cleavage in the acylperoxoiron(III)-porphyrin intermediate [(P)Fe(III)-OOX] (P = porphyrin) were successfully recorded and characterized. The results clearly indicate that the O-O bond in m-CPBA is heterolytically cleaved by the studied iron(III)-porphyrin complexes independent of the acidity of the reaction medium. The existence of two different oxidation products under acidic and basic conditions is suggested not to be the result of a mechanistic changeover in the mode of O-O bond cleavage on going from low to high pH values, but rather the effect of environmental changes on the actual product of the O-O bond cleavage in [(P)Fe(III)-OOX]. The oxoiron(IV)-porphyrin cation radical formed as a primary oxidation product over the entire pH range can undergo a one- or two-electron reduction depending on the selected reaction conditions. The present study provides valuable information for the interpretation and improved understanding of results obtained in product-analysis experiments.

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Section: Resultssupporting

confidence: 60%

“…The use of only a small excess of oxidant accelerates the heterolytic OO bond cleavage in [(TMP)Fe III OOC(O)Ar] and leads to the formation of the oxoiron(IV)–porphyrin cation radical [(TMP + . )Fe IV O] 13. Herein, we focused on the final product of the oxidation of [Fe III (TMP)] by m ‐CPBA in acetonitrile under basic conditions.…”

Section: Resultsmentioning

confidence: 99%

Factors That Affect the Nature of the Final Oxidation Products in “Peroxo‐Shunt” Reactions of Iron–Porphyrin Complexes

Franke

Wolak

Eldik

2009

Chemistry A European J

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“…Several typical substrates were chosen, such as cyclohexene12k and bicyclo[2.2.1]hept‐2‐ene (BICY)12b for epoxidation, 9,10‐dihydroanthracene (DHA)12o for CH bond activation, and dimethylsulfide (DMS)12n for heteroatom oxidation (see Scheme for the structures of the studied substrates and their main oxidation products).…”

Section: Introductionmentioning

confidence: 99%

Combined Experimental and Theoretical Study on the Reactivity of Compounds I and II in Horseradish Peroxidase Biomimetics

Franke

Brindell

et al. 2014

Chemistry A European J

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For the exploration of the intrinsic reactivity of two key active species in the catalytic cycle of horseradish peroxidase (HRP), Compound I (HRP-I) and Compound II (HRP-II), we generated in situ [Fe(IV) O(TMP(+.) )(2-MeIm)](+) and [Fe(IV) O(TMP)(2-MeIm)](0) (TMP=5,10,15,20-tetramesitylporphyrin; 2-MeIm=2-methylimidazole) as biomimetics for HRP-I and HRP-II, respectively. Their catalytic activities in epoxidation, hydrogen abstraction, and heteroatom oxidation reactions were studied in acetonitrile at -15 °C by utilizing rapid-scan UV/Vis spectroscopy. Comparison of the second-order rate constants measured for the direct reactions of the HRP-I and HRP-II mimics with the selected substrates clearly confirmed the outstanding oxidizing capability of the HRP-I mimic, which is significantly higher than that of HRP-II. The experimental study was supported by computational modeling (DFT calculations) of the oxidation mechanism of the selected substrates with the involvement of quartet and doublet HRP-I mimics ((2,4) Cpd I) and the closed-shell triplet spin HRP-II model ((3) Cpd II) as oxidizing species. The significantly lower activation barriers calculated for the oxidation systems involving (2,4) Cpd I than those found for (3) Cpd II are in line with the much higher oxidizing efficiency of the HRP-I mimic proven in the experimental part of the study. In addition, the DFT calculations show that all three reaction types catalyzed by HRP-I occur on the doublet spin surface in an effectively concerted manner, whereas these reactions may proceed in a stepwise mechanism with the HRP-II mimic as oxidant. However, the high desaturation or oxygen rebound barriers during CH bond activation processes by the HRP-II mimic predict a sufficient lifetime for the substrate radical formed through hydrogen abstraction. Thus, the theoretical calculations suggest that the dissociation of the substrate radical may be a more favorable pathway than desaturation or oxygen rebound processes. Importantly, depending on the electronic nature of the oxidizing species, that is, (2,4) Cpd I or (3) Cpd II, an interesting region-selective conversion phenomenon between sulfoxidation and H-atom abstraction was revealed in the course of the oxidation reaction of dimethylsulfide. The combined experimental and theoretical study on the elucidation of the intrinsic reactivity patterns of the HRP-I and HRP-II mimics provides a valuable tool for evaluating the particular role of the HRP active species in biological systems.

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“…10 Some work supported the notion that Cpd0 is a competent oxidant for the transformation of sulfides by using carefully designed oxidation systems. Among others, these involve 1) a synthetic stable ligand, such as corrole and corrolazine, instead of a sensitive porphyrin ligand,11, 12 2) a Mn complex instead of a Fe complex,13, 14 and 3) the use of m ‐chloroperoxybenzoic acid (mCPBA) instead of H 2 O 2 15. 16 In addition, little effort has been devoted to demonstrate that these stabilized complexes are identical to the putative intermediates participating in the biochemical processes.…”

Section: Introductionmentioning

confidence: 99%

Evidence of Two Key Intermediates Contributing to the Selectivity of P450‐Biomimetic Oxidation of Sulfides to Sulfoxides and Sulfones

Zhou¹,

Chen²,

Jin³

et al. 2012

Chemistry An Asian Journal

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A mild process for the selective oxidation of sulfides is in great demand. Therefore, probing the mechanism underlying the biological oxidation of sulfides under ambient conditions may provide valuable insights for the development of such a reaction. Based on porphyrin models of P450 enzymes, evidence of two key intermediates, Int0 and Int1, in this reaction is provided. Spectroscopic studies indicated the formation of a hydroperoxide-iron(III) species (Int0) upon addition of H(2)O(2). This intermediate proved to be highly selective for sulfoxide production. By contrast, a defined porphyrin oxoiron(IV) cation radical (Int1) directly reacted with sulfoxides, leading selectively to the corresponding sulfones. Interestingly, the available sulfoxides reversibly act as a new axial ligand for Int0 forming a more active species Int0(SO). The amount of Int0 increased in the presence of alkyl, aryl, or aromatic sulfides, while Int1 formed in the absence of these sulfides. Thus, sulfoxides and sulfones would selectively form under conditions that favor the corresponding intermediates, which elucidate the biological oxidation pathway.

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Welches Oxidationsmittel ist wirklich verantwortlich für Oxygenierungen an P450‐Modellsystemen? – Eine kinetische Betrachtung

Cited by 15 publications

References 23 publications

Factors That Affect the Nature of the Final Oxidation Products in “Peroxo‐Shunt” Reactions of Iron–Porphyrin Complexes

Factors That Affect the Nature of the Final Oxidation Products in “Peroxo‐Shunt” Reactions of Iron–Porphyrin Complexes

Combined Experimental and Theoretical Study on the Reactivity of Compounds I and II in Horseradish Peroxidase Biomimetics

Evidence of Two Key Intermediates Contributing to the Selectivity of P450‐Biomimetic Oxidation of Sulfides to Sulfoxides and Sulfones

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