Mechanistic Questions about the Reaction of Molecular Oxygen with Palladium in Oxidase Catalysis

Gligorich, Keith M.; Sigman, Matthew S.

doi:10.1002/anie.200602138

Cited by 206 publications

(65 citation statements)

References 39 publications

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“…Thus, assuming the rate law in eq. 1 can be extended to low [H 2 O 2 ], if hydrogen peroxide were to be generated during the course of aerobic oxidations with 1, as commonly proposed, 5,8,20 it would be disproportionated more rapidly than the diols would be oxidized. The current data are not conclusive as to whether free H 2 O 2 is released during catalysis, or whether Pd-O 2 intermediates such as 4, 5, and 8 react without releasing H 2 O 2 .…”

Section: Shown Inmentioning

confidence: 97%

Catalytic Role of Multinuclear Palladium–Oxygen Intermediates in Aerobic Oxidation Followed by Hydrogen Peroxide Disproportionation

et al. 2015

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Aerobic oxidation of alcohols are catalyzed by the Pd-acetate compound [LPd(OAc)]2(OTf)2 (L = neocuproine = 2,9-dimethyl-1,10-phenanthroline) to form ketones and the release of hydrogen peroxide, but the latter rapidly undergoes disproportionation. We employ a series of kinetic and isotope labeling studies made largely possible by electrospray ionization mass spectrometry to determine the role of intermediates in causing this complex chemical transformation. The data suggested that multiple catalytic paths for H2O2 disproportionation occur, which involve formation and consumption of multinuclear Pd species. We find that the trinuclear compound [(LPd)3(μ(3)-O)2](2+), which we have identified in a previous study, is a product of dioxygen activation that is formed during aerobic oxidations of alcohols catalyzed by [LPd(OAc)]2(OTf)2. It is also a product of hydrogen peroxide activation during disproportionation reactions catalyzed by [LPd(OAc)]2(OTf)2. The results suggest that this trinuclear Pd compound is involved in one of the simultaneous mechanisms for the reduction of oxygen and/or the disproportionation of hydrogen peroxide during oxidation catalysis. Electrospray ionization mass spectrometry of hydrogen peroxide disproportionation reactions suggested the presence of other multinuclear Pd-O2 species in solution. Theoretical calculations of these compounds yield some insight into their structure and potential chemistry.

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Section: Shown Inmentioning

confidence: 97%

Catalytic Role of Multinuclear Palladium–Oxygen Intermediates in Aerobic Oxidation Followed by Hydrogen Peroxide Disproportionation

et al. 2015

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“…The catalysis can be broken down into two distinct half reactions, wherein the first half is oxidation and/or functionalization of the organic substrate, which occurs independently of the catalyst regeneration step (Scheme 1). 4 Molecular oxygen can be used as the terminal oxidant in combination with two equivalents of a Brønsted acid to regenerate the active catalyst with concomitant formation of hydrogen peroxide. These transformations have been termed “oxidase” type reactions because they are inspired by enzyme oxidases wherein substrate oxidation does not occur by oxygen atom transfer 3a.…”

Section: Introductionmentioning

confidence: 99%

Recent advancements and challenges of palladiumII-catalyzed oxidation reactions with molecular oxygen as the sole oxidant

2009

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During the past 10 years there have been significant advances in PdII-catalyzed oxidation reactions where the use of ligands has led to the development of catalytic systems capable of achieving high turnover numbers, which employ molecular oxygen as the sole stoichiometric oxidant. This Feature article will highlight some of the recent developments in direct molecular oxygen-coupled PdII-catalyzed oxidation reactions with an emphasis on enhanced catalytic systems and new reactions. Additionally, limitations of current catalytic systems, such as ligand oxidation, are presented and their implications for the development of new reactions are discussed.

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“…[22] In the present study, we employed the longer timescales (minutes to hours) accessed Figure 1. [9,10] [9,10] …”

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Trinuclear Pd₃O₂ Intermediate in Aerobic Oxidation Catalysis

et al. 2014

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The activation of O2 is a key step in selective catalytic aerobic oxidation reactions mediated by transition metals. The bridging trinuclear palladium species, [(LPd(II))3(μ(3)-O)2](2+) (L=2,9-dimethylphenanthroline), was identified during the [LPd(OAc)]2(OTf)2-catalyzed aerobic oxidation of 1,2-propanediol. Independent synthesis, structural characterization, and catalytic studies of the trinuclear compound show that it is a product of oxygen activation by reduced palladium species and is a competent intermediate in the catalytic aerobic oxidation of alcohols. The formation and catalytic activity of the trinuclear Pd3O2 species illuminates a multinuclear pathway for aerobic oxidation reactions catalyzed by Pd complexes.

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Mechanistic Questions about the Reaction of Molecular Oxygen with Palladium in Oxidase Catalysis

Cited by 206 publications

References 39 publications

Catalytic Role of Multinuclear Palladium–Oxygen Intermediates in Aerobic Oxidation Followed by Hydrogen Peroxide Disproportionation

Catalytic Role of Multinuclear Palladium–Oxygen Intermediates in Aerobic Oxidation Followed by Hydrogen Peroxide Disproportionation

Recent advancements and challenges of palladiumII-catalyzed oxidation reactions with molecular oxygen as the sole oxidant

Trinuclear Pd₃O₂ Intermediate in Aerobic Oxidation Catalysis

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Mechanistic Questions about the Reaction of Molecular Oxygen with Palladium in Oxidase Catalysis

Cited by 206 publications

References 39 publications

Catalytic Role of Multinuclear Palladium–Oxygen Intermediates in Aerobic Oxidation Followed by Hydrogen Peroxide Disproportionation

Catalytic Role of Multinuclear Palladium–Oxygen Intermediates in Aerobic Oxidation Followed by Hydrogen Peroxide Disproportionation

Recent advancements and challenges of palladiumII-catalyzed oxidation reactions with molecular oxygen as the sole oxidant

Trinuclear Pd3O2 Intermediate in Aerobic Oxidation Catalysis

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Trinuclear Pd₃O₂ Intermediate in Aerobic Oxidation Catalysis