Evidence for parallel destructive, and competitive epoxidation and dismutation pathways in metalloporphyrin-catalysed alkene oxidation by hydrogen peroxide

Cunningham, Ian D.; Danks, Timothy N.; Hay, J. N.; Hamerton, Ian; Gunathilagan, Suthahari

doi:10.1016/s0040-4020(01)00639-1

Cited by 38 publications

(54 citation statements)

References 30 publications

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“…The process of intramolecular catalyst destruction can involve the metallo-oxo intermediate (8) [20,27,28], but also a metallo-oxo intermediate (10) [29,30] which is formed from (8) by reaction with hydrogen peroxide [16,31]. Analogous processes have been suggested in iron metalloporphyrin catalysis [7,8] (Scheme 4).…”

Section: Resultsmentioning

confidence: 90%

“…One possibility is the intramolecular decomposition of the highly active species (path a) by a process similar to the described ring destruction in supported metalloporphyrins [14,15]. Other processes of macrocycle destruction of intermolecular nature are the oxidation of another molecule of catalyst by the active oxidant species (path b) or the generation of oxygen radical's by interaction with H 2 O 2 , which can destroy the catalyst (path c) [8,16] (Scheme 1).…”

Section: Resultsmentioning

confidence: 99%

“…Under condition B, Mn-1 (see entry 2, Table 1) preferentially follows pathway B with the formation of a metallo-oxo intermediate (8) which has to be, in this case, the oxidising species. This intermediate has enough activity for alkene epoxidation (II), but does not attack the Zn macrocycle (III).…”

Section: Resultsmentioning

confidence: 99%

“…Two pathways are possible for this degradation: intramolecular decomposition [25] or attack of water or hydrogen peroxide molecules to the metallo-oxo intermediate (8) [7,26]. The more or less pronounced radical character of (8) can be an important way of distinguishing which pathway is operative.…”

Section: Resultsmentioning

confidence: 99%

“…Many studies have simply not considered this problem or circunvented it by performing reactions in the presence of an excess of substrate. However, some recent publications highlight the importance of catalyst stability in hydrogen peroxide oxidations [7][8][9].…”

Section: Introductionmentioning

confidence: 99%

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A view on the mechanism of metalloporphyrin degradation in hydrogen peroxide epoxidation reactions

Serra

Marçalo

Gonsalves

2004

Journal of Molecular Catalysis A: Chemical

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The stability of biomimetic catalysts is an essential characteristic for them to be of some practical use. The study of the reaction of metalloporphyrin catalysts in hydrogen peroxide oxidations in the presence of benzoic acid allowed to understand whether an intramolecular or intermolecular mechanism is operative in catalyst degradation. Under certain reaction conditions, the presence of a radical inhibitor minimises the catalyst degradation, and therefore, improves the catalytic process.

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Section: Resultsmentioning

confidence: 90%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

A view on the mechanism of metalloporphyrin degradation in hydrogen peroxide epoxidation reactions

Serra

Marçalo

Gonsalves

2004

Journal of Molecular Catalysis A: Chemical

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Catalyst Stability Determines the Catalytic Activity of Non‐Heme Iron Catalysts in the Oxidation of Alkanes

et al. 2008

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A series of iron(II) bis(triflate) complexes [Fe(L)(OTf) 2 ] containing linear tetradentate bis(pyridylmethyl) diamine ligands with a range of ligand backbones has been prepared. The backbone of the ligand series has been varied from a two-carbon linkage (ethylene (1), 4,5-dichlorophenylene (2) and cyclohexyl (3)) to a three-carbon (propyl (4)) and a four-carbon linkage (butyl (5)). The coordination geometries of these complexes have been investigated in the solid state by X-ray crystallography and in solution by 1 H and 19 F NMR spectroscopy. Due to the labile nature of high spin iron(II) complexes in solution, dynamic equilibria of complexes with different coordination geometries (cis-α, cis-β and trans) are observed with ligands 2-5. In these cases, the geometry observed in the solid state does not necessarily represent the only or even the major geometry present in solution. The ligand field strength in the various complexes has been investigated by VT magnetic moment measurements and UV-vis spectroscopy. The strongest ligand field is observed with the most rigid ligands 1 and 2, which generate complexes [Fe(L)(OTf) 2 ] with a cis-α coordination geometry and the corresponding complexes [Fe(L)(CH 3 CN) 2 ] 2+ displays spin crossover behaviour. The catalytic properties of the complexes for the oxidation of cyclohexane, using hydrogen peroxide as the oxidant, have been investigated. An increased flexibility in the ligand results in a weaker ligand field, which increases the lability of the complexes. The activity and selectivity of the catalysts appear to be related to the strength of the ligand field and the stability of the catalyst in the oxidising environment.2

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Biomimetic Iron‐Catalyzed Asymmetric Epoxidations: Fundamental Concepts, Challenges and Opportunities

Gelalcha

2014

Adv Synth Catal

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The state-of-the-art in the non-enzymatic iron-catalyzed asymmetric epoxidation of C=C double bonds is reviewed within the broader context of biomimetic oxidation catalysis. After introducing fundamental concepts of oxygen activation in nature and by man, historical landmarks, recent breakthroughs, scopes and limitations in relation to existing methodologies and their impact on future directions are assessed, focusing mainly on progress made in the last five years.

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Evidence for parallel destructive, and competitive epoxidation and dismutation pathways in metalloporphyrin-catalysed alkene oxidation by hydrogen peroxide

Cited by 38 publications

References 30 publications

A view on the mechanism of metalloporphyrin degradation in hydrogen peroxide epoxidation reactions

A view on the mechanism of metalloporphyrin degradation in hydrogen peroxide epoxidation reactions

Catalyst Stability Determines the Catalytic Activity of Non‐Heme Iron Catalysts in the Oxidation of Alkanes

Biomimetic Iron‐Catalyzed Asymmetric Epoxidations: Fundamental Concepts, Challenges and Opportunities

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