O2-promoted allylic acetoxylation of alkenes: Assessment of "push" versus "pull" mechanisms and comparison between O2 and benzoquinone

Tianning Diao, Shannon S. Stahl

Research output: Contribution to journalArticle

Abstract

Palladium-catalyzed acetoxylation of allylic C-H bonds has been the subject of extensive study. These reactions proceed via allyl-palladium(II) intermediates that react with acetate to afford the allyl acetate product. Benzoquinone and molecular oxygen are two common oxidants for these reactions. Benzoquinone has been shown to promote allyl acetate formation from well-defined π-allyl palladium(II) complexes. Here, we assess the ability of O2 to promote similar reactions with a series of "unligated" π-allyl palladium(II) complexes (i.e., in the absence of ancillary phosphorus, nitrogen or related donor ligands). Stoichiometric and catalytic allyl acetate formation is observed under aerobic conditions with several different alkenes. Mechanistic studies are most consistent with a "pull" mechanism in which O2 traps the Pd0 intermediate following reversible C-O bond formation from an allyl-palladium(II) species. A "push" mechanism, involving oxidatively induced C-O bond formation, does not appear to participate. These results and conclusions are compared with benzoquinone-promoted allylic acetoxylation, in which a "push" mechanism seems to be operative.

Original languageEnglish (US)
Pages (from-to)96-102
Number of pages7
JournalPolyhedron
Volume84
DOIs
StatePublished - Dec 14 2014

Fingerprint

Palladium
Alkenes
quinones
alkenes
Olefins
palladium
acetates
Molecular oxygen
Oxidants
Phosphorus
phosphorus
Acetates
Nitrogen
Ligands
benzoquinone
traps
nitrogen
ligands
oxygen
products

Keywords

  • Aerobic
  • Allylic
  • C-H activation
  • Oxidation
  • Palladium

ASJC Scopus subject areas

  • Inorganic Chemistry
  • Materials Chemistry
  • Physical and Theoretical Chemistry

Cite this

O2-promoted allylic acetoxylation of alkenes : Assessment of "push" versus "pull" mechanisms and comparison between O2 and benzoquinone. / Diao, Tianning; Stahl, Shannon S.

In: Polyhedron, Vol. 84, 14.12.2014, p. 96-102.

Research output: Contribution to journalArticle

@article{d16cc2c1bd0f4fa485284052a28f1f82,
title = "O2-promoted allylic acetoxylation of alkenes: Assessment of {"}push{"} versus {"}pull{"} mechanisms and comparison between O2 and benzoquinone",
abstract = "Palladium-catalyzed acetoxylation of allylic C-H bonds has been the subject of extensive study. These reactions proceed via allyl-palladium(II) intermediates that react with acetate to afford the allyl acetate product. Benzoquinone and molecular oxygen are two common oxidants for these reactions. Benzoquinone has been shown to promote allyl acetate formation from well-defined π-allyl palladium(II) complexes. Here, we assess the ability of O2 to promote similar reactions with a series of {"}unligated{"} π-allyl palladium(II) complexes (i.e., in the absence of ancillary phosphorus, nitrogen or related donor ligands). Stoichiometric and catalytic allyl acetate formation is observed under aerobic conditions with several different alkenes. Mechanistic studies are most consistent with a {"}pull{"} mechanism in which O2 traps the Pd0 intermediate following reversible C-O bond formation from an allyl-palladium(II) species. A {"}push{"} mechanism, involving oxidatively induced C-O bond formation, does not appear to participate. These results and conclusions are compared with benzoquinone-promoted allylic acetoxylation, in which a {"}push{"} mechanism seems to be operative.",
keywords = "Aerobic, Allylic, C-H activation, Oxidation, Palladium",
author = "Tianning Diao and Stahl, {Shannon S.}",
year = "2014",
month = "12",
day = "14",
doi = "10.1016/j.poly.2014.06.038",
language = "English (US)",
volume = "84",
pages = "96--102",
journal = "Polyhedron",
issn = "0277-5387",
publisher = "Elsevier Limited",

}

TY - JOUR

T1 - O2-promoted allylic acetoxylation of alkenes

T2 - Assessment of "push" versus "pull" mechanisms and comparison between O2 and benzoquinone

AU - Diao, Tianning

AU - Stahl, Shannon S.

PY - 2014/12/14

Y1 - 2014/12/14

N2 - Palladium-catalyzed acetoxylation of allylic C-H bonds has been the subject of extensive study. These reactions proceed via allyl-palladium(II) intermediates that react with acetate to afford the allyl acetate product. Benzoquinone and molecular oxygen are two common oxidants for these reactions. Benzoquinone has been shown to promote allyl acetate formation from well-defined π-allyl palladium(II) complexes. Here, we assess the ability of O2 to promote similar reactions with a series of "unligated" π-allyl palladium(II) complexes (i.e., in the absence of ancillary phosphorus, nitrogen or related donor ligands). Stoichiometric and catalytic allyl acetate formation is observed under aerobic conditions with several different alkenes. Mechanistic studies are most consistent with a "pull" mechanism in which O2 traps the Pd0 intermediate following reversible C-O bond formation from an allyl-palladium(II) species. A "push" mechanism, involving oxidatively induced C-O bond formation, does not appear to participate. These results and conclusions are compared with benzoquinone-promoted allylic acetoxylation, in which a "push" mechanism seems to be operative.

AB - Palladium-catalyzed acetoxylation of allylic C-H bonds has been the subject of extensive study. These reactions proceed via allyl-palladium(II) intermediates that react with acetate to afford the allyl acetate product. Benzoquinone and molecular oxygen are two common oxidants for these reactions. Benzoquinone has been shown to promote allyl acetate formation from well-defined π-allyl palladium(II) complexes. Here, we assess the ability of O2 to promote similar reactions with a series of "unligated" π-allyl palladium(II) complexes (i.e., in the absence of ancillary phosphorus, nitrogen or related donor ligands). Stoichiometric and catalytic allyl acetate formation is observed under aerobic conditions with several different alkenes. Mechanistic studies are most consistent with a "pull" mechanism in which O2 traps the Pd0 intermediate following reversible C-O bond formation from an allyl-palladium(II) species. A "push" mechanism, involving oxidatively induced C-O bond formation, does not appear to participate. These results and conclusions are compared with benzoquinone-promoted allylic acetoxylation, in which a "push" mechanism seems to be operative.

KW - Aerobic

KW - Allylic

KW - C-H activation

KW - Oxidation

KW - Palladium

UR - http://www.scopus.com/inward/record.url?scp=84911421872&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84911421872&partnerID=8YFLogxK

U2 - 10.1016/j.poly.2014.06.038

DO - 10.1016/j.poly.2014.06.038

M3 - Article

AN - SCOPUS:84911421872

VL - 84

SP - 96

EP - 102

JO - Polyhedron

JF - Polyhedron

SN - 0277-5387

ER -