Hydroxylation and epoxidation catalyzed by iron-porphine complexes. Oxygen transfer from iodosylbenzene

Groves, John T.; Nemo, Thomas E.; Myers, Richard S.

doi:10.1021/ja00498a040

Cited by 813 publications

(363 citation statements)

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“…It is a very useful substrate and frequently used for the Fe III porphyrin-catalyzed hydroxylation by iodosylbenzene (PhIO) 6,10,37,38 and was used as test reaction to compare the catalyst activity of the iron porphyrins. The results are presented in Table 1 The low solubility of the iron porphyrins in a CH 2 Cl 2 :CH 3 CN (1:1 v/v ratio) solvent mixture in homogeneous catalysis certainly is an important factor responsible for the low yields (and low turnover number -TN) of the iron porphyrin itself.…”

Section: Resultsmentioning

confidence: 99%

“…The possibility of the molecular interaction of the Fe(TDFSPP) species in solution could be another reason for the low catalytic activity observed in the homogeneous catalysis because it can be accompanied by μ-oxo complex formation. 17,[37][38][39] The oxidative degradation of the catalyst in solution is frequently responsible for the low yield in catalytic reactions using metalloporphyrins 17 but not for second generation iron porphyrins and in cases with a low FePor/oxidant molar ratio such as was used in run 1 (1:50).…”

Section: Resultsmentioning

confidence: 99%

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Catalytic activity in oxidation reactions of anionic iron(III) porphyrins immobilized on raw and grafted chrysotile

Nakagaki¹,

Castro²,

Machado³

et al. 2006

J. Braz. Chem. Soc.

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Crisotila natural e quimicamente modificada foi usada como matrizes para imobilização de ferroporfirinas de segunda geração. As atividades catalíticas dos sólidos obtidos foram avaliadas em reações de oxidação de cicloexano, usando iodosilbenzeno como oxidante. Os resultados de catálise foram analisados e comparados aos obtidos pela imobilização das mesmas ferroporfirinas em sílica funcionalizada com 3-APTS, derivadas do tratamento ácido da crisotila. Os resultados preliminares mostraram que os catalisadores são eficientes e seletivos para a obtenção de álcool.Natural and grafted chrysotile were used as matrices for the immobilization of second generation iron porphyrins. The catalysts obtained were evaluated in the oxidation reaction of cyclohexane, using iodosylbenzene as oxidant agent. The catalyst activity for different conditions was compared with results for the same porphyrins immobilized with 3-APTS grafted disordered silica, obtained from acid-leached chrysotile. Preliminary results have shown that high activity can be obtained with short reaction times, and that the reaction is specific for alcohol.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Catalytic activity in oxidation reactions of anionic iron(III) porphyrins immobilized on raw and grafted chrysotile

Nakagaki¹,

Castro²,

Machado³

et al. 2006

J. Braz. Chem. Soc.

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“…Systems-To address the issue of whether the selectivity of P450 3A4 reaction is dominated by the lability of C-H bonds, the P450 3A4 reaction was compared with reactions done with relatively simple biomimetic models, Fe and Mn (meso)-tetraphenylporphine/PhI ϭ O systems (83,84). Reactions were done under limited turnover conditions, with testosterone in excess.…”

Section: Regioselectivity Of Testosterone Oxidations Catalyzed By Biomentioning

confidence: 99%

Cytochrome P450 3A4-catalyzed Testosterone 6β-Hydroxylation Stereochemistry, Kinetic Deuterium Isotope Effects, and Rate-limiting Steps

Krauser

Guengerich

2005

Journal of Biological Chemistry

101

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Testosterone 6␤-hydroxylation is a prototypic reaction of cytochrome P450 (P450) 3A4, the major human P450. Biomimetic reactions produced a variety of testosterone oxidation products with 6␤-hydroxylation being only a minor reaction, indicating that P450 3A4 has considerable control over the course of steroid hydroxylation because 6␤-hydroxylation is not dominant in a thermodynamically controlled oxidation of the substrate. Several isotopically labeled testosterone substrates were prepared and used to probe the catalytic mechanism of P450 3A4: (i) 2,2,4,6,6-2 H 5 ; (ii) 6,6-2 H 2 ; (iii) 6␣-2 H; (iv) 6␤-2 H; and (v) 6␤-3 H testosterone. Only the 6␤-hydrogen was removed by P450 3A4 and not the 6␣, indicating that P450 3A4 abstracts hydrogen and rebounds oxygen only at the ␤ face. Analysis of the rates of hydroxylation of 6␤-1 H-, 6␤-2 H-, and 6␤-3 Hlabeled testosterone and application of the Northrop method yielded an apparent intrinsic kinetic deuterium isotope effect ( D k) of 15. The deuterium isotope effects on k cat and k cat /K m in non-competitive reactions were only 2-3. Some "switching" to other hydroxylations occurred because of 6␤-2 H substitution. The high D k value is consistent with an initial hydrogen atom abstraction reaction. Attenuation of the high D k in the non-competitive experiments implies that C-H bond breaking is not a dominant rate-limiting step. Considerable attenuation of a high D k value was also seen with a slower P450 3A4 reaction, the O-dealkylation of 7-benzyloxyquinoline. Thus P450 3A4 is an enzyme with regioselective flexibility but also considerable regioselectivity and stereoselectivity in product formation, not necessarily dominated by the ease of C-H bond breaking. P4501 enzymes are found in organisms from Archebacter to humans and catalyze oxidations of a great variety of chemicals (1, 2). The human P450s are the major enzymes involved in the clearance of drugs, and P450 3A4, the most abundant P450 in liver and small intestine, is involved in the oxidation of one-half of the drugs used today (3, 4). Two crystal structures of P450 3A4 have been published recently (5, 6); however, neither has a substrate bound in a position amenable to oxidation. P450 3A4 exhibits heterotropic and homotropic cooperativity in some but not all of its reactions (4, 7-10), and several models have been proposed to explain such behavior (9,(11)(12)(13)(14)(15). A view frequently expressed for smaller substrates is that binding is relatively loose and the regioselectivity of oxidation of substrates is largely a function of the ease of C-H bond breaking (16,17).Relatively little information is available regarding what step is rate-limiting in P450 3A4 reactions. The addition of the first electron in the catalytic cycle (step 2 of Scheme 1) is apparently relatively fast in the presence of an optimal concentration of NADPH-P450 reductase (18). Only limited information has been obtained regarding steps 1 and 3-9 (Scheme 1) with P450 3A4 reactions. Without information on the extent to which chemical step...

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“…Many stable oxo-transition metal complexes are known and have been characterized, but several of these complexes are inert and non-reactive as oxygen transfer reagents. Groves and coworkers 13 described the use of meso-tetraphenylporphyriniron(III) chloride (TPP) in combination with the lipophilic iodosylbenzene, first used in vivo by Ullrich, for the epoxidation of olefins, and the hydroxylation of alkanes. Literature survey reveals that no report was available on the kinetics of oxidation of mesotetraphenylporphyriniron(III) chloride catalysed oxidation of indole, hence we have carried out this work with magnesiummonoperoxyphthalate (MMPP).…”

Section: Introductionmentioning

confidence: 99%

Kinetics and Mechanism of Meso-Tetraphenylporphyriniron(iii) Chloride (Tpp) Catalysed Oxidation of Indole by Magnesiummono Peroxyphthalate

Durairaj¹,

Karunakaran²

2012

Int J Pharmceut Chem

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ABSTRACT:Mechanistic study on meso-tetraphenylporphyriniron(III) chloride (TPP) catalysed oxidation of indole by magnesiummonoperoxyphthalate in aqueous acetonitrile medium have been carried out. The reaction follows a fractional order with respect to substrate and catalyst. The order with respect to oxidant was found to be one. Increase in percentage of acetonitrile and increase in the concentration of [H + ] decreased the rate.The reaction fails to initiate polymerization, and a radical mechanism is ruled out. Activation and thermodynamic parameters have been computed. A suitable kinetic scheme based on these observations is proposed. Significant catalytic activity is observed for the reaction system in the presence of TPP.

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Hydroxylation and epoxidation catalyzed by iron-porphine complexes. Oxygen transfer from iodosylbenzene

Cited by 813 publications

References 3 publications

Catalytic activity in oxidation reactions of anionic iron(III) porphyrins immobilized on raw and grafted chrysotile

Catalytic activity in oxidation reactions of anionic iron(III) porphyrins immobilized on raw and grafted chrysotile

Cytochrome P450 3A4-catalyzed Testosterone 6β-Hydroxylation Stereochemistry, Kinetic Deuterium Isotope Effects, and Rate-limiting Steps

Kinetics and Mechanism of Meso-Tetraphenylporphyriniron(iii) Chloride (Tpp) Catalysed Oxidation of Indole by Magnesiummono Peroxyphthalate

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