Synergic sedation of sensitive anions: alkali-mediated zincation of cyclic ethers and ethene

A.R. Kennedy, J. Klett, R.E. Mulvey, D.S. Wright

Research output: Contribution to journalArticle

100 Citations (Scopus)

Abstract

Deprotonation of alkyl and vinyl carbon-hydrogen bonds for synthetic purposes is often hindered not merely by the need for an exceptionally strong base, but by the inherent instability of the resultant anion. Metalation of cyclic ethers adjacent to oxygen, for example, has invariably initiated a ring-opening decomposition pathway. Here, we show that the use of a bimetallic base can overcome such instability through a cooperative combination of zinc-carbon and sodium-oxygen bonding. Both tetrahydrofuran and tetrahydropyran reacted cleanly over days at room temperature to yield alpha-zinc-substituted products that were sufficiently stable to be isolated and crystallographically characterized. A related zincation-anion trapping strategy, with sodium replaced by potassium, induced clean deprotonation of ethene to yield a stable product. Preliminary electrophilic quenching experiments with the alpha-zinc-substituted cyclic ethers and benzoyl chloride gave satisfactory yields of the tetrahydrofuran-derived ketone but only trace amounts of the tetrahydropyran-derived ketone.
LanguageEnglish
Pages706-708
Number of pages3
JournalScience
Volume326
Issue number5953
DOIs
Publication statusPublished - 30 Oct 2009

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Cyclic Ethers
Alkalies
Anions
Zinc
Deprotonation
Ketones
Carbon
Sodium
Oxygen
Quenching
Potassium
Hydrogen bonds
Decomposition
ethylene
Experiments
Temperature
tetrahydrofuran

Keywords

  • deprotonative matalation
  • magnesium
  • metals
  • bases
  • aryl

Cite this

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abstract = "Deprotonation of alkyl and vinyl carbon-hydrogen bonds for synthetic purposes is often hindered not merely by the need for an exceptionally strong base, but by the inherent instability of the resultant anion. Metalation of cyclic ethers adjacent to oxygen, for example, has invariably initiated a ring-opening decomposition pathway. Here, we show that the use of a bimetallic base can overcome such instability through a cooperative combination of zinc-carbon and sodium-oxygen bonding. Both tetrahydrofuran and tetrahydropyran reacted cleanly over days at room temperature to yield alpha-zinc-substituted products that were sufficiently stable to be isolated and crystallographically characterized. A related zincation-anion trapping strategy, with sodium replaced by potassium, induced clean deprotonation of ethene to yield a stable product. Preliminary electrophilic quenching experiments with the alpha-zinc-substituted cyclic ethers and benzoyl chloride gave satisfactory yields of the tetrahydrofuran-derived ketone but only trace amounts of the tetrahydropyran-derived ketone.",
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Synergic sedation of sensitive anions : alkali-mediated zincation of cyclic ethers and ethene. / Kennedy, A.R.; Klett, J.; Mulvey, R.E.; Wright, D.S.

In: Science, Vol. 326, No. 5953, 30.10.2009, p. 706-708.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Synergic sedation of sensitive anions

T2 - Science

AU - Kennedy, A.R.

AU - Klett, J.

AU - Mulvey, R.E.

AU - Wright, D.S.

PY - 2009/10/30

Y1 - 2009/10/30

N2 - Deprotonation of alkyl and vinyl carbon-hydrogen bonds for synthetic purposes is often hindered not merely by the need for an exceptionally strong base, but by the inherent instability of the resultant anion. Metalation of cyclic ethers adjacent to oxygen, for example, has invariably initiated a ring-opening decomposition pathway. Here, we show that the use of a bimetallic base can overcome such instability through a cooperative combination of zinc-carbon and sodium-oxygen bonding. Both tetrahydrofuran and tetrahydropyran reacted cleanly over days at room temperature to yield alpha-zinc-substituted products that were sufficiently stable to be isolated and crystallographically characterized. A related zincation-anion trapping strategy, with sodium replaced by potassium, induced clean deprotonation of ethene to yield a stable product. Preliminary electrophilic quenching experiments with the alpha-zinc-substituted cyclic ethers and benzoyl chloride gave satisfactory yields of the tetrahydrofuran-derived ketone but only trace amounts of the tetrahydropyran-derived ketone.

AB - Deprotonation of alkyl and vinyl carbon-hydrogen bonds for synthetic purposes is often hindered not merely by the need for an exceptionally strong base, but by the inherent instability of the resultant anion. Metalation of cyclic ethers adjacent to oxygen, for example, has invariably initiated a ring-opening decomposition pathway. Here, we show that the use of a bimetallic base can overcome such instability through a cooperative combination of zinc-carbon and sodium-oxygen bonding. Both tetrahydrofuran and tetrahydropyran reacted cleanly over days at room temperature to yield alpha-zinc-substituted products that were sufficiently stable to be isolated and crystallographically characterized. A related zincation-anion trapping strategy, with sodium replaced by potassium, induced clean deprotonation of ethene to yield a stable product. Preliminary electrophilic quenching experiments with the alpha-zinc-substituted cyclic ethers and benzoyl chloride gave satisfactory yields of the tetrahydrofuran-derived ketone but only trace amounts of the tetrahydropyran-derived ketone.

KW - deprotonative matalation

KW - magnesium

KW - metals

KW - bases

KW - aryl

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