The functionalization of saturated hydrocarbons. Part 20. Alkyl hydroperoxides: reaction intermediates in the oxidation of saturated hydrocarbons by Gif-type reactions and mechanistic studies on their formation

Barton, D. H. R.; Bévière, Stéphane D.; Chavasiri, Warinthorn; Csuhai, Eva; Doller, Darı́o; Liu, Wei Guo

doi:10.1021/ja00032a032

Cited by 124 publications

(39 citation statements)

References 3 publications

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“…The low value of the intrinsic kinetic isotope effect ( [34,351 but no evidence for such a species has been reported. What is clear however, is that the much larger kinetic isotope effect (>7) for oxidation of the -CH, group in toluene is entirely consistent with a linear transition state and is too large to arise from a four-center transition state.…”

Section: Mechanistic Discussionmentioning

confidence: 99%

Further Evidence for Multiple Pathways in Soluble Methane‐Monooxygenase‐Catalysed Oxidations from the Measurement of Deuterium Kinetic Isotope Effects

Wilkins

Dalton

Samuel

et al. 1994

European Journal of Biochemistry

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The data from the deuterium isotope experiments in this study show that the primary kinetic isotope effect for methane oxidation catalysed by soluble methane monooxygenase from Methylococcus capsulatus (Bath) is very small, <2. In contrast, the primary kinetic isotope effect for -CH, group oxidation in toluene is large, > 7. A mechanistic pathway in which a substrate radical is formed from hydrogen atom abstraction by a ferry1 species is believed to operate for CH,, the toluene -CH, group and similar alkanes. Direct oxygen atom addition, rather than H atom abstraction, is indicated for aromatic ring oxidations in benzene and toluene and for styrene oxide formation from styrene. Thus, more than one mechanistic pathway appears to operate in soluble methanemonooxygenase-catalysed reactions and, in some cases, the pathway chosen may be dictated by the substrate.In the soluble methane-monooxygenase-catalysed oxidation of toluene the rates of: (a) substrate dissociation from the enzyme-substrate complex, (b) product formation and (c) product release (benzyl alcohol and p-cresol) from the enzyme-product complex are comparable in magnitude. Therefore all three of these steps are partially rate-determining in the soluble methane monooxygenase catalytic cycle for toluene oxidation.The active site of the enzyme soluble methane monooxygenase [l] is just one example of the bridged diiron motif now known to occur in a number of non-heme iron proteins of vastly different functions [2]. In the case of soluble methane monooxygenase the function of the diiron site is to activate 0, so that one of the oxygen atoms is inserted into a methane C-H bond to form methanol. The other oxygen atom ends up in the second product, water. The enzyme consists of three components : the hydroxylase, the reductase and a regulatory protein, component B. The p-OH bridged diiron site [3, 41 resides in the hydroxylase and it is the fully reduced, Fe(II)Fe(II), form which is catalytically active [5]. 25).National Institutes of Health.high-valent iron-oxo intermediate, forming a substrate radical which then rapidly reacts with iron-bound OH to produce the product [9-111. This mechanism is, in many respects, similar to that proposed for cytochrome P-450 (121. It has been shown that P-450-catalysed hydroxylation of toluene produces benzyl alcohol plus o-, m-and p-cresols with benzyl alcohol as the major product [13 1. With fully deuterated toluene the product ratio was reversed and the cresols dominated. We had earlier observed that catalysis of toluene oxidation by soluble methane monooxygenase produced benzyl alcohol and only p-cresol (not ortho and metu) [8,9, 141. Recently Rataj et al. [15] reported that benzyl alcohol alone and no p-cresol was produced in this oxidation of toluene using soluble methane monooxygenase from Methylosinus trichosporium and crude extract from Methylococcus cupsulutus (Bath). They were also unable to detect any styrene oxide when styrene was used as substrate, a product we had observed previously with the M. cupsulutus ...

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Section: Mechanistic Discussionmentioning

confidence: 99%

Further Evidence for Multiple Pathways in Soluble Methane‐Monooxygenase‐Catalysed Oxidations from the Measurement of Deuterium Kinetic Isotope Effects

Wilkins

Dalton

Samuel

et al. 1994

European Journal of Biochemistry

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“…[3] Further study of the F$II-H202 reaction showed that bromotrichloromethane and its congeners afford bromination instead of oxidation. The selectivity is the same as the oxidation reaction and does not follow a typical radical bromination pattern.…”

Section: Methodsmentioning

confidence: 99%

Models for non-heme oxidation enzymes

Barton¹,

Taylor²

1996

Pure and Applied Chemistry

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The Gif systems for the selective functionalization of saturated hydrocarbons based on the reactions of superoxide with Feu and of hydrogen peroxide with FelI1 are described. [l] Both systems are relatively efficient, but not nearly so efficient as the electrochemical system developed in collaboration with Prof. G.Balavoine and Dr. Aurore Gref (Universite de Paris-Sud-Orsay, France).[2] All systems afford main1 ketones. This is an unusual selectivity which implies a non-radical mechanism. It has been proven for the FeIIl H202 system that the activation of the Fe*II is independent of the formation of ketone which comes from oxygen. The intermediate for the ketone is a hydroperoxide (derived from oxygen). [3] Recent mechanistic studies are reported. INI1pODUClTONThere is universal acceptance that the selective functionalization of saturated hydrocarbons is a research challenge of major proportions. Although paraffins are, as their name implies, usually considered to be inert, Nature has solved the problem of their functionalization using complexes of iron and, to a lesser extent of copper. The iron complexes are either heme based, as in the ubiquitous P450 enzymes, or non-heme based, as in the vitally important roline-4-hydroxylase and in the fascinating enzyme, methane monooxygenase. These enzymes contain one FJ1, or two FelI1 atoms bridged by an 0x0 bridge, respectively. Although the protein in these enzymes is responsible for their chemo-and stereo-selectivity, the fundamental activation of the iron should be seen also in appropriate models. Models of P450 enzymes have been known for decades and the work of J.T.Groves is particularly noteworthy in this respect. Models of non-heme iron enzymes are much less familiar and, until our publications on Gif type Chemistry, not efficacious.[5] USE OF SUPEROXIDE AND OF HKDROGEN PEROXIDEOur work started with the assumption that when, 3 billion years ago, the blue-green algae started to make oxygen, a unicellular form of life started to concert the oxidation of iron with the oxidation of saturated hydrocarbons. It is agreed that after 1 billion years of life under reductive conditions, the world was full of saturated hydrocarbons, FeI1 compounds and metallic iron, as well as, an abundance of hydrogen sulfide, since life was using the reduction of sulfate to sulfide as an energy source.So our first experiment to test our hypothesis was the oxidation of adamantane in pyridine with some acetic acid in the presence of iron powder, hydrogen sulfide and oxygen. Surprisingly, a major amount of adamantanone was formed and there was only minor formation of the tertiary alcohol. Later, we obtained the same results when we replaced the iron powder with zinc powder and added a catalytic amount of an FdI salt. This showed the unusual power of the iron species formed to make ketones as principal products. During systematic studies on adamantane oxidation, we examined the effect of reducing oxygen pressure. We were surprised to find that lowering the oxy en pressure increased th...

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“…Other colleagues are also begining to find some advantage in the use of UHP [60,61,62]. A UHP method has been used as a reagent in the synthesis of the brassinolide side chain [61], and in a GoAgg" reaction UHP has been used as an alternative to anhydrous hydrogen peroxide [62]. There are still problems to be resolved but the way forward is clear and it is anticipated that reagents of the type reviewed will be developed within the next few years that will progress the control of oxidation processes.…”

Section: Discussionmentioning

confidence: 97%

“…In addition the range of oxidation reactions that can be effected has also widened. Other colleagues are also begining to find some advantage in the use of UHP [60,61,62]. A UHP method has been used as a reagent in the synthesis of the brassinolide side chain [61], and in a GoAgg" reaction UHP has been used as an alternative to anhydrous hydrogen peroxide [62].…”

Section: Discussionmentioning

confidence: 99%

Novel organic peroxygen reagents for use in organic synthesis

Heaney

1993

Organic Peroxygen Chemistry

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The functionalization of saturated hydrocarbons. Part 20. Alkyl hydroperoxides: reaction intermediates in the oxidation of saturated hydrocarbons by Gif-type reactions and mechanistic studies on their formation

Cited by 124 publications

References 3 publications

Further Evidence for Multiple Pathways in Soluble Methane‐Monooxygenase‐Catalysed Oxidations from the Measurement of Deuterium Kinetic Isotope Effects

Further Evidence for Multiple Pathways in Soluble Methane‐Monooxygenase‐Catalysed Oxidations from the Measurement of Deuterium Kinetic Isotope Effects

Models for non-heme oxidation enzymes

Novel organic peroxygen reagents for use in organic synthesis

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