Mechanism of Catalytic Oxidation of Styrenes with Hydrogen Peroxide in the Presence of Cationic Palladium(II) Complexes

Katherine Walker, Laura Dornan, Richard Zare, Robert Waymouth, Mark Muldoon

Research output: Contribution to journalArticle

12 Citations (Scopus)
236 Downloads (Pure)

Abstract

Kinetic studies, isotope labeling, and in situ high-resolution mass spectrometry are used to elucidate the mechanism for the catalytic oxidation of styrenes using aqueous hydrogen peroxide (H2O2) and the cationic palladium(II) compound, [(PBO)Pd(NCMe)2][OTf]2 (PBO = 2-(pyridin-2-yl)benzoxazole). Previous studies have shown that this reaction yields acetophenones with high selectivity. We find that H2O2 binds to Pd(II) followed by styrene binding to generate a Pd-alkylperoxide that liberates acetophenone by at least two competitive processes, one of which involves a palladium enolate intermediate that has not been previously observed in olefin oxidation reactions. We suggest that acetophenone is formed from the palladium enolate intermediate by protonation from H2O2. We replaced hydrogen peroxide with t-butyl hydroperoxide and found that, although the palladium enolate intermediate was observed, it was not on the major product-generating pathway, indicating that the form of the oxidant plays a key role in the reaction mechanism.
Original languageEnglish
JournalJournal of the American Chemical Society
DOIs
Publication statusPublished - 29 Aug 2017

Fingerprint

Styrenes
Catalytic oxidation
Palladium
Hydrogen peroxide
Hydrogen Peroxide
Styrene
Palladium compounds
Acetophenones
Benzoxazoles
tert-Butylhydroperoxide
Protonation
Alkenes
Isotope Labeling
Oxidants
Isotopes
Labeling
Olefins
Mass spectrometry
Mass Spectrometry
Oxidation

Cite this

@article{62544dda196d483da80526bf55ade787,
title = "Mechanism of Catalytic Oxidation of Styrenes with Hydrogen Peroxide in the Presence of Cationic Palladium(II) Complexes",
abstract = "Kinetic studies, isotope labeling, and in situ high-resolution mass spectrometry are used to elucidate the mechanism for the catalytic oxidation of styrenes using aqueous hydrogen peroxide (H2O2) and the cationic palladium(II) compound, [(PBO)Pd(NCMe)2][OTf]2 (PBO = 2-(pyridin-2-yl)benzoxazole). Previous studies have shown that this reaction yields acetophenones with high selectivity. We find that H2O2 binds to Pd(II) followed by styrene binding to generate a Pd-alkylperoxide that liberates acetophenone by at least two competitive processes, one of which involves a palladium enolate intermediate that has not been previously observed in olefin oxidation reactions. We suggest that acetophenone is formed from the palladium enolate intermediate by protonation from H2O2. We replaced hydrogen peroxide with t-butyl hydroperoxide and found that, although the palladium enolate intermediate was observed, it was not on the major product-generating pathway, indicating that the form of the oxidant plays a key role in the reaction mechanism.",
author = "Katherine Walker and Laura Dornan and Richard Zare and Robert Waymouth and Mark Muldoon",
year = "2017",
month = "8",
day = "29",
doi = "10.1021/jacs.7b05413",
language = "English",
journal = "Journal of the American Chemical Society",
issn = "0002-7863",
publisher = "American Chemical Society",

}

Mechanism of Catalytic Oxidation of Styrenes with Hydrogen Peroxide in the Presence of Cationic Palladium(II) Complexes. / Walker, Katherine ; Dornan, Laura; Zare, Richard ; Waymouth, Robert ; Muldoon, Mark.

In: Journal of the American Chemical Society, 29.08.2017.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Mechanism of Catalytic Oxidation of Styrenes with Hydrogen Peroxide in the Presence of Cationic Palladium(II) Complexes

AU - Walker, Katherine

AU - Dornan, Laura

AU - Zare, Richard

AU - Waymouth, Robert

AU - Muldoon, Mark

PY - 2017/8/29

Y1 - 2017/8/29

N2 - Kinetic studies, isotope labeling, and in situ high-resolution mass spectrometry are used to elucidate the mechanism for the catalytic oxidation of styrenes using aqueous hydrogen peroxide (H2O2) and the cationic palladium(II) compound, [(PBO)Pd(NCMe)2][OTf]2 (PBO = 2-(pyridin-2-yl)benzoxazole). Previous studies have shown that this reaction yields acetophenones with high selectivity. We find that H2O2 binds to Pd(II) followed by styrene binding to generate a Pd-alkylperoxide that liberates acetophenone by at least two competitive processes, one of which involves a palladium enolate intermediate that has not been previously observed in olefin oxidation reactions. We suggest that acetophenone is formed from the palladium enolate intermediate by protonation from H2O2. We replaced hydrogen peroxide with t-butyl hydroperoxide and found that, although the palladium enolate intermediate was observed, it was not on the major product-generating pathway, indicating that the form of the oxidant plays a key role in the reaction mechanism.

AB - Kinetic studies, isotope labeling, and in situ high-resolution mass spectrometry are used to elucidate the mechanism for the catalytic oxidation of styrenes using aqueous hydrogen peroxide (H2O2) and the cationic palladium(II) compound, [(PBO)Pd(NCMe)2][OTf]2 (PBO = 2-(pyridin-2-yl)benzoxazole). Previous studies have shown that this reaction yields acetophenones with high selectivity. We find that H2O2 binds to Pd(II) followed by styrene binding to generate a Pd-alkylperoxide that liberates acetophenone by at least two competitive processes, one of which involves a palladium enolate intermediate that has not been previously observed in olefin oxidation reactions. We suggest that acetophenone is formed from the palladium enolate intermediate by protonation from H2O2. We replaced hydrogen peroxide with t-butyl hydroperoxide and found that, although the palladium enolate intermediate was observed, it was not on the major product-generating pathway, indicating that the form of the oxidant plays a key role in the reaction mechanism.

UR - http://pubs.acs.org/doi/abs/10.1021/jacs.7b05413

U2 - 10.1021/jacs.7b05413

DO - 10.1021/jacs.7b05413

M3 - Article

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

SN - 0002-7863

ER -