Distinguishing Biomimetic Oxidations from Oxidations Mediated by Freely Diffusing Radicals

Ingold, K. U.; MacFaul, Philip A.

doi:10.1142/9781848160699_0002

Cited by 37 publications

(32 citation statements)

References 50 publications

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“…The consensus mechanism involves hydrogen atom abstraction from the substrate (R-H) by a reactive iron-oxo intermediate followed by rapid transfer of the metal-bound oxygen atom to an intermediate caged alkyl radical. This so-called oxygen rebound mechanism [13] is consistent with the stereochemical, regiochemical and allylic scrambling results observed in the hydroxylation of diagnostic substrates by cytochrome P450 and rules out freely diffusing radicals [14] and direct oxygen insertion processes.…”

Section: Synthetic Oxometalloporphyrins As Models For Cytochrome P450supporting

confidence: 77%

Reactivity and mechanisms of metalloporphyrin-catalyzed oxidations

Groves

2000

J. Porphyrins Phthalocyanines

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Effective systems for the catalytic oxygenation of hydrocarbons have been developed based on metalloporphyrins containing iron, manganese and ruthenium. These metalloporphyrin catalysts were inspired by studies of the mechanism of the heme oxygenase cytochrome P450 and related enzymes. Oxometalloporphyrins, which have now been spectroscopically characterized, have very high reactivity as oxygen transfer agents. A combination of experimental and computational methods has begun to provide an understanding of the structure and reactivity of these oxometalloporphyrin complexes and the mechanisms of oxygen transfer reactions they catalyze.

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Section: Synthetic Oxometalloporphyrins As Models For Cytochrome P450supporting

confidence: 77%

Reactivity and mechanisms of metalloporphyrin-catalyzed oxidations

Groves

2000

J. Porphyrins Phthalocyanines

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“…As the reaction proceeds, the Fe−O bond length for the O atom that reacts with an H atom of CH 4 increases in length from 1.699 to 1.783 Å, whereas the other Fe−O bond length decreases from about 1.699 to 1.650 Å. The intermediate Z[(HO)FeO(CH 3 • )] is similar in character to that proposed in biological systems . This state is apparently not stable.…”

Section: Resultsmentioning

confidence: 62%

Density Functional Theory Investigations of the Direct Oxidation of Methane on an Fe-Exchanged Zeolite

et al. 2004

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The reactions of methane with [FeO 2 ] + and [OFeO)] + cations exchanged into ZSM-5 have been investigated using density functional theory. Experimental evidence for the latter cation has recently been reported on the basis of EXAFS experiments performed on Fe-ZSM-5 with Fe/Al ) 0.17-0.80. Of the two iron-containing species investigated, Z[OFeO] [Z here represents the cation-exchange site in the zeolite] is lower in energy by 7.7 kcal/mol, assuming a spin multiplicity M ) 6. The activation energy for the conversion of Z[FeO 2 ] and Z[OFeO] is 10.0 kcal/mol. The activation of methane occurs preferentially on Z [OFeO]. Weakly adsorbed methane reacts with Z[OFeO] to produce a weakly bound CH 3 • free radical. The activation barrier for this process is 15.9 kcal/mol. The methyl radical then reacts via a barrierless process to form Z[(OH)Fe(OCH 3 )]. This product is very stable thermally, but can be converted to adsorbed methanol or formaldehyde via processes exhibiting high activation barriers (∼39.3 kcal/mol in both cases). Hydrolysis of Z[(OH)Fe(OCH 3 )] to form adsorbed methanol is practically thermoneutral and has an activation barrier of 6.2 kcal/mol. The desorption of the adsorbed methanol is endothermic by 18.8 kal/mol, but the formation of water from the resulting Z[Fe(OH) 2 ] has a moderately high activation barrier of 37.9 kcal/mol. If N 2 O is present in the gas phase, the activation barrier for the formation of H 2 O decreases to 18.1 kcal/mol. The results of the present investigation are qualitatively consistent with recent experimental observations.

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“…Among peroxides, only those with good leaving groups are able to transfer an oxygen atom on a metalloporphyrin in order to generate a high-valent metal−oxo species. The reactivity of alkylhydroperoxides in the presence of transition metals, specially distinguishing oxidation involving metal−oxo species from autoxidation reactions, has been pertinently reviewed. , …”

Section: Resultsmentioning

confidence: 99%

Alkylating Capacity and Reaction Products of Antimalarial Trioxanes after Activation by a Heme Model

2002

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The reactivity of 1,2,4-trioxane molecules 2-5, structurally related to the antimalarial drug artemisinin, with a heme model, manganese(II) tetraphenylporphyrin, is reported. With the pharmacologically active drugs 2-4, covalent adducts were obtained by addition of a drug-derived radical onto the porphyrin macrocycle, whereas no reaction was obtained with the nonactive compound 5. This confirms that alkylation is probably one of the key factors of the pharmacological activity of endoperoxide-based antimalarial drugs.

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Distinguishing Biomimetic Oxidations from Oxidations Mediated by Freely Diffusing Radicals

Cited by 37 publications

References 50 publications

Reactivity and mechanisms of metalloporphyrin-catalyzed oxidations

Reactivity and mechanisms of metalloporphyrin-catalyzed oxidations

Density Functional Theory Investigations of the Direct Oxidation of Methane on an Fe-Exchanged Zeolite

Alkylating Capacity and Reaction Products of Antimalarial Trioxanes after Activation by a Heme Model

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