Dual roles for potassium hydride in haloarene reduction: CSNAr and SET reduction via organic electron donors formed in benzene

Joshua P. Barham, Samuel E. Dalton, Mark Allison, Giuseppe Nocera, Allan Young, Matthew P. John, Thomas McGuire, Sébastien Campos, Tell Tuttle, John A. Murphy

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

Potassium hydride behaves uniquely and differently than sodium hydride towards aryl halides. Its reactions with a range of haloarenes, including designed 2,6-dialkylhaloarenes, were studied in THF and in benzene. In THF, evidence supports concerted nucleophilic aromatic substitution, CSNAr, and the mechanism originally proposed by Pierre et al. is now validated through DFT studies. In benzene, besides this pathway, strong evidence for single electron transfer chemistry is reported. Experimental observations and DFT studies lead us to propose organic super electron donor generation to initiate BHAS (base-promoted homolytic aromatic substitution) cycles. Organic donor formation originates from deprotonation of benzene by KH; attack on benzene by the resulting phenylpotassium generates phenylcyclohexadienylpotassium that can undergo (i) deprotonation to form an organic super electron donor or (ii) hydride loss to afford biphenyl. Until now, BHAS reactions have been triggered by reaction of a base, MOtBu (M = K, Na), with many different types of organic additive, all containing heteroatoms (N or O or S) that enhance their acidity and place them within range of MOtBu as a base. This paper shows that with the stronger base, KH, even a hydrocarbon (benzene) can be converted into an electron-donating initiator.
LanguageEnglish
Pages11510-11518
Number of pages9
JournalJournal of the American Chemical Society
Volume140
Issue number36
Early online date17 Aug 2018
DOIs
Publication statusE-pub ahead of print - 17 Aug 2018

Fingerprint

Benzene
Hydrides
Potassium
Electrons
Deprotonation
Substitution reactions
Discrete Fourier transforms
Hydrocarbons
Acidity
Sodium

Keywords

  • potassium hydride
  • sodium hydride
  • ahaloarene reduction
  • benzene

Cite this

Barham, Joshua P. ; Dalton, Samuel E. ; Allison, Mark ; Nocera, Giuseppe ; Young, Allan ; John, Matthew P. ; McGuire, Thomas ; Campos, Sébastien ; Tuttle, Tell ; Murphy, John A. / Dual roles for potassium hydride in haloarene reduction : CSNAr and SET reduction via organic electron donors formed in benzene. In: Journal of the American Chemical Society. 2018 ; Vol. 140, No. 36. pp. 11510-11518.
@article{5dea47a898044a1694228bc430965fec,
title = "Dual roles for potassium hydride in haloarene reduction: CSNAr and SET reduction via organic electron donors formed in benzene",
abstract = "Potassium hydride behaves uniquely and differently than sodium hydride towards aryl halides. Its reactions with a range of haloarenes, including designed 2,6-dialkylhaloarenes, were studied in THF and in benzene. In THF, evidence supports concerted nucleophilic aromatic substitution, CSNAr, and the mechanism originally proposed by Pierre et al. is now validated through DFT studies. In benzene, besides this pathway, strong evidence for single electron transfer chemistry is reported. Experimental observations and DFT studies lead us to propose organic super electron donor generation to initiate BHAS (base-promoted homolytic aromatic substitution) cycles. Organic donor formation originates from deprotonation of benzene by KH; attack on benzene by the resulting phenylpotassium generates phenylcyclohexadienylpotassium that can undergo (i) deprotonation to form an organic super electron donor or (ii) hydride loss to afford biphenyl. Until now, BHAS reactions have been triggered by reaction of a base, MOtBu (M = K, Na), with many different types of organic additive, all containing heteroatoms (N or O or S) that enhance their acidity and place them within range of MOtBu as a base. This paper shows that with the stronger base, KH, even a hydrocarbon (benzene) can be converted into an electron-donating initiator.",
keywords = "potassium hydride, sodium hydride, ahaloarene reduction, benzene",
author = "Barham, {Joshua P.} and Dalton, {Samuel E.} and Mark Allison and Giuseppe Nocera and Allan Young and John, {Matthew P.} and Thomas McGuire and S{\'e}bastien Campos and Tell Tuttle and Murphy, {John A.}",
year = "2018",
month = "8",
day = "17",
doi = "10.1021/jacs.8b07632",
language = "English",
volume = "140",
pages = "11510--11518",
journal = "Journal of the American Chemical Society",
issn = "0002-7863",
publisher = "American Chemical Society",
number = "36",

}

Dual roles for potassium hydride in haloarene reduction : CSNAr and SET reduction via organic electron donors formed in benzene. / Barham, Joshua P.; Dalton, Samuel E.; Allison, Mark; Nocera, Giuseppe; Young, Allan; John, Matthew P.; McGuire, Thomas; Campos, Sébastien; Tuttle, Tell; Murphy, John A.

In: Journal of the American Chemical Society, Vol. 140, No. 36, 17.08.2018, p. 11510-11518.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Dual roles for potassium hydride in haloarene reduction

T2 - Journal of the American Chemical Society

AU - Barham, Joshua P.

AU - Dalton, Samuel E.

AU - Allison, Mark

AU - Nocera, Giuseppe

AU - Young, Allan

AU - John, Matthew P.

AU - McGuire, Thomas

AU - Campos, Sébastien

AU - Tuttle, Tell

AU - Murphy, John A.

PY - 2018/8/17

Y1 - 2018/8/17

N2 - Potassium hydride behaves uniquely and differently than sodium hydride towards aryl halides. Its reactions with a range of haloarenes, including designed 2,6-dialkylhaloarenes, were studied in THF and in benzene. In THF, evidence supports concerted nucleophilic aromatic substitution, CSNAr, and the mechanism originally proposed by Pierre et al. is now validated through DFT studies. In benzene, besides this pathway, strong evidence for single electron transfer chemistry is reported. Experimental observations and DFT studies lead us to propose organic super electron donor generation to initiate BHAS (base-promoted homolytic aromatic substitution) cycles. Organic donor formation originates from deprotonation of benzene by KH; attack on benzene by the resulting phenylpotassium generates phenylcyclohexadienylpotassium that can undergo (i) deprotonation to form an organic super electron donor or (ii) hydride loss to afford biphenyl. Until now, BHAS reactions have been triggered by reaction of a base, MOtBu (M = K, Na), with many different types of organic additive, all containing heteroatoms (N or O or S) that enhance their acidity and place them within range of MOtBu as a base. This paper shows that with the stronger base, KH, even a hydrocarbon (benzene) can be converted into an electron-donating initiator.

AB - Potassium hydride behaves uniquely and differently than sodium hydride towards aryl halides. Its reactions with a range of haloarenes, including designed 2,6-dialkylhaloarenes, were studied in THF and in benzene. In THF, evidence supports concerted nucleophilic aromatic substitution, CSNAr, and the mechanism originally proposed by Pierre et al. is now validated through DFT studies. In benzene, besides this pathway, strong evidence for single electron transfer chemistry is reported. Experimental observations and DFT studies lead us to propose organic super electron donor generation to initiate BHAS (base-promoted homolytic aromatic substitution) cycles. Organic donor formation originates from deprotonation of benzene by KH; attack on benzene by the resulting phenylpotassium generates phenylcyclohexadienylpotassium that can undergo (i) deprotonation to form an organic super electron donor or (ii) hydride loss to afford biphenyl. Until now, BHAS reactions have been triggered by reaction of a base, MOtBu (M = K, Na), with many different types of organic additive, all containing heteroatoms (N or O or S) that enhance their acidity and place them within range of MOtBu as a base. This paper shows that with the stronger base, KH, even a hydrocarbon (benzene) can be converted into an electron-donating initiator.

KW - potassium hydride

KW - sodium hydride

KW - ahaloarene reduction

KW - benzene

UR - https://pubs.acs.org/loi/jacsat

U2 - 10.1021/jacs.8b07632

DO - 10.1021/jacs.8b07632

M3 - Article

VL - 140

SP - 11510

EP - 11518

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

SN - 0002-7863

IS - 36

ER -