Cytochrome P-450 Model Systems: Alkene Oxidation

Traylor, Teddy G.; Dunlap, Beth E.; Miksztal, Andrew R.

doi:10.1007/978-1-4684-5568-7_78

Cited by 2 publications

(1 citation statement)

References 7 publications

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“…A large body of work has been dedicated to the study of PFe-catalyzed alkane oxidation using dioxygen as the stoichiometric oxidant. − ,− ,,,− Although electron-deficient PFe complexes are competent to catalyze isobutane oxidation at moderate temperatures without the input of stoichiometric reductants, such simple catalysts are not stable under the autoxidation reaction conditions. While porphyrin ring halogenation leads to more robust epoxidation catalysts that utilize PFe III complexes and an O atom donor to produce reactive compound I analogues (P •+ Fe IV O), ,, PFe alkane hydroxylation catalysts that derive their oxidizing equivalents from O 2 that are based on highly halogenated Br 8 (C 6 F 5 ) 4 PH 2 ligand systems possess stabilities that are diminished relative to those of analogous catalysts that feature (C 6 F 5 ) 4 PH 2 and (C 3 F 7 ) 4 PH 2 ligand frameworks.…”

Section: Discussionmentioning

confidence: 99%

Mechanistic Studies of (Porphinato)Iron-Catalyzed Isobutane Oxidation. Comparative Studies of Three Classes of Electron-Deficient Porphyrin Catalysts

2000

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We report herein a comprehensive study of (porphinato)iron [PFe]-catalyzed isobutane oxidation in which molecular oxygen is utilized as the sole oxidant; these catalytic reactions were carried out and monitored in both autoclave reactors and sapphire NMR tubes. In situ 19F and 13C NMR experiments, coupled with GC analyses and optical spectra obtained from the autoclave reactions have enabled the identification of the predominant porphyrinic species present during PFe-catalyzed oxidation of isobutane. Electron-deficient PFe catalysts based on 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin [(C6F5)4PH2], 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(pentafluorophenyl) porphyrin [Br8(C6F5)4PH2], and 5,10,15,20-tetrakis(heptafluoropropyl) porphyrin [(C3F7)4PH2] macrocycles were examined. The nature and distribution of hydrocarbon oxidation products show that an autoxidation reaction pathway dominates the reaction kinetics, consistent with a radical chain process. For each catalytic system examined, PFeII species were shown not to be stable under moderate O2 pressure at 80 degrees C; in every case, the PFeII catalyst precursor was converted quantitatively to high-spin PFeIII complexes prior to the observation of any hydrocarbon oxidation products. Once catalytic isobutane oxidation is initiated, all reactions are marked by concomitant decomposition of the porphyrin-based catalyst. In situ 17O NMR spectroscopic studies confirm the incorporation of 17O from labeled water into the oxidation products, implicating the involvement of PFe-OH in the catalytic cycle. Importantly, Br8(C6F5)4PFe-based catalysts, which lack macrocycle C-H bonds, do not exhibit augmented stability with respect to analogous catalysts based on (C6F5)4PFe and (C3F7)4PFe species. The data presented are consistent with a hydrocarbon oxidation process in which PFe complexes play dual roles of radical chain initiator, and the species responsible for the catalytic decomposition of organic peroxides. This modified Haber-Weiss reaction scheme provides for the decomposition of tert-butyl hydroperoxide intermediates via reaction with PFe-OH complexes; the PFeIII species responsible for hydroperoxide decomposition are regenerated by reaction of PFeII with dioxygen under these experimental conditions.

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Section: Discussionmentioning

confidence: 99%

Mechanistic Studies of (Porphinato)Iron-Catalyzed Isobutane Oxidation. Comparative Studies of Three Classes of Electron-Deficient Porphyrin Catalysts

2000

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Iron compounds and the mechanisms of the homogeneous catalysis of the activation of O₂and H₂O₂and of the oxidation of organic substrates

Sychev¹,

Isak²

1995

Russ. Chem. Rev.

165

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Cytochrome P-450 Model Systems: Alkene Oxidation

Cited by 2 publications

References 7 publications

Mechanistic Studies of (Porphinato)Iron-Catalyzed Isobutane Oxidation. Comparative Studies of Three Classes of Electron-Deficient Porphyrin Catalysts

Mechanistic Studies of (Porphinato)Iron-Catalyzed Isobutane Oxidation. Comparative Studies of Three Classes of Electron-Deficient Porphyrin Catalysts

Iron compounds and the mechanisms of the homogeneous catalysis of the activation of O₂and H₂O₂and of the oxidation of organic substrates

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Cytochrome P-450 Model Systems: Alkene Oxidation

Cited by 2 publications

References 7 publications

Mechanistic Studies of (Porphinato)Iron-Catalyzed Isobutane Oxidation. Comparative Studies of Three Classes of Electron-Deficient Porphyrin Catalysts

Mechanistic Studies of (Porphinato)Iron-Catalyzed Isobutane Oxidation. Comparative Studies of Three Classes of Electron-Deficient Porphyrin Catalysts

Iron compounds and the mechanisms of the homogeneous catalysis of the activation of O2and H2O2and of the oxidation of organic substrates

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Iron compounds and the mechanisms of the homogeneous catalysis of the activation of O₂and H₂O₂and of the oxidation of organic substrates