Trapping, stabilization, and characterization of an enolate anion of a 1,6-adduct of benzophenone chelated by a sodium alkylamidozincate cation

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Abstract

There has been a recent upsurge of activity in the study of alkali metal zincate reagents due to their often special reactivity/selectivity in, for example, deprotonative metalation and nucleophilic addition reactions. Heteroleptic dialkylamidozincates, [M+Zn(R)2(NR'2)-], usually transfer selectivity of the amide ligand to electrophiles. Here, in contrast, it is reported that the sodium zincate [TMEDA·Na(-tBu)(-TMP)Zn(tBu)] reacts as an alkylating agent toward the diaryl ketone benzophenone (Ph2C=O), selectively adding one of its tBu ligands to the para-C atom of one of the Ph rings. The reaction can be carried out at room temperature, which is a decided advantage over lithium reagents as these are generally utilized at subambient temperatures. The stabilizing effect of the bimetallic (Na, Zn) cationic residue of the starting zincate reagent in coordinating to the dearomatized enolate anion of the 1,6-addition adduct allows the adduct to be isolated in a pure crystalline form. An X-ray crystallographic study of the adduct reveals a molecular structure based on a near-planar, four-element (NaOZnN) ring with a TMP-N and an enolato-O bridge. The Na and Zn atoms also carry terminal TMEDA (N,N'-attached) and tBu (C-attached) ligands, respectively. Also included are 1H/13C NMR spectroscopic data for the adduct when dissolved in cyclohexane-d12 solution.
LanguageEnglish
Pages13106-13107
Number of pages1
JournalJournal of the American Chemical Society
Volume127
Issue number38
DOIs
Publication statusPublished - 30 Aug 2005

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Thymidine Monophosphate
Anions
Cations
Negative ions
Stabilization
Positive ions
Sodium
Ligands
Alkali Metals
Atoms
Addition reactions
Temperature
Alkylating Agents
Alkali metals
Cyclohexane
Molecular Structure
Ketones
Lithium
Amides
Molecular structure

Keywords

  • alkali metal zincate reagents
  • Heteroleptic dialkylamidozincates
  • room temperature
  • spectroscopic data

Cite this

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title = "Trapping, stabilization, and characterization of an enolate anion of a 1,6-adduct of benzophenone chelated by a sodium alkylamidozincate cation",
abstract = "There has been a recent upsurge of activity in the study of alkali metal zincate reagents due to their often special reactivity/selectivity in, for example, deprotonative metalation and nucleophilic addition reactions. Heteroleptic dialkylamidozincates, [M+Zn(R)2(NR'2)-], usually transfer selectivity of the amide ligand to electrophiles. Here, in contrast, it is reported that the sodium zincate [TMEDA·Na(-tBu)(-TMP)Zn(tBu)] reacts as an alkylating agent toward the diaryl ketone benzophenone (Ph2C=O), selectively adding one of its tBu ligands to the para-C atom of one of the Ph rings. The reaction can be carried out at room temperature, which is a decided advantage over lithium reagents as these are generally utilized at subambient temperatures. The stabilizing effect of the bimetallic (Na, Zn) cationic residue of the starting zincate reagent in coordinating to the dearomatized enolate anion of the 1,6-addition adduct allows the adduct to be isolated in a pure crystalline form. An X-ray crystallographic study of the adduct reveals a molecular structure based on a near-planar, four-element (NaOZnN) ring with a TMP-N and an enolato-O bridge. The Na and Zn atoms also carry terminal TMEDA (N,N'-attached) and tBu (C-attached) ligands, respectively. Also included are 1H/13C NMR spectroscopic data for the adduct when dissolved in cyclohexane-d12 solution.",
keywords = "alkali metal zincate reagents, Heteroleptic dialkylamidozincates, room temperature, spectroscopic data",
author = "E. Hevia and G.W. Honeyman and A.R. Kennedy and R.E. Mulvey",
year = "2005",
month = "8",
day = "30",
doi = "10.1021/ja053756c",
language = "English",
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journal = "Journal of the American Chemical Society",
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TY - JOUR

T1 - Trapping, stabilization, and characterization of an enolate anion of a 1,6-adduct of benzophenone chelated by a sodium alkylamidozincate cation

AU - Hevia, E.

AU - Honeyman, G.W.

AU - Kennedy, A.R.

AU - Mulvey, R.E.

PY - 2005/8/30

Y1 - 2005/8/30

N2 - There has been a recent upsurge of activity in the study of alkali metal zincate reagents due to their often special reactivity/selectivity in, for example, deprotonative metalation and nucleophilic addition reactions. Heteroleptic dialkylamidozincates, [M+Zn(R)2(NR'2)-], usually transfer selectivity of the amide ligand to electrophiles. Here, in contrast, it is reported that the sodium zincate [TMEDA·Na(-tBu)(-TMP)Zn(tBu)] reacts as an alkylating agent toward the diaryl ketone benzophenone (Ph2C=O), selectively adding one of its tBu ligands to the para-C atom of one of the Ph rings. The reaction can be carried out at room temperature, which is a decided advantage over lithium reagents as these are generally utilized at subambient temperatures. The stabilizing effect of the bimetallic (Na, Zn) cationic residue of the starting zincate reagent in coordinating to the dearomatized enolate anion of the 1,6-addition adduct allows the adduct to be isolated in a pure crystalline form. An X-ray crystallographic study of the adduct reveals a molecular structure based on a near-planar, four-element (NaOZnN) ring with a TMP-N and an enolato-O bridge. The Na and Zn atoms also carry terminal TMEDA (N,N'-attached) and tBu (C-attached) ligands, respectively. Also included are 1H/13C NMR spectroscopic data for the adduct when dissolved in cyclohexane-d12 solution.

AB - There has been a recent upsurge of activity in the study of alkali metal zincate reagents due to their often special reactivity/selectivity in, for example, deprotonative metalation and nucleophilic addition reactions. Heteroleptic dialkylamidozincates, [M+Zn(R)2(NR'2)-], usually transfer selectivity of the amide ligand to electrophiles. Here, in contrast, it is reported that the sodium zincate [TMEDA·Na(-tBu)(-TMP)Zn(tBu)] reacts as an alkylating agent toward the diaryl ketone benzophenone (Ph2C=O), selectively adding one of its tBu ligands to the para-C atom of one of the Ph rings. The reaction can be carried out at room temperature, which is a decided advantage over lithium reagents as these are generally utilized at subambient temperatures. The stabilizing effect of the bimetallic (Na, Zn) cationic residue of the starting zincate reagent in coordinating to the dearomatized enolate anion of the 1,6-addition adduct allows the adduct to be isolated in a pure crystalline form. An X-ray crystallographic study of the adduct reveals a molecular structure based on a near-planar, four-element (NaOZnN) ring with a TMP-N and an enolato-O bridge. The Na and Zn atoms also carry terminal TMEDA (N,N'-attached) and tBu (C-attached) ligands, respectively. Also included are 1H/13C NMR spectroscopic data for the adduct when dissolved in cyclohexane-d12 solution.

KW - alkali metal zincate reagents

KW - Heteroleptic dialkylamidozincates

KW - room temperature

KW - spectroscopic data

UR - http://dx.doi.org/10.1021/ja053756c

U2 - 10.1021/ja053756c

DO - 10.1021/ja053756c

M3 - Article

VL - 127

SP - 13106

EP - 13107

JO - Journal of the American Chemical Society

T2 - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

SN - 0002-7863

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