Structurally defined potassium-mediated zincation of pyridine and 4-R-substituted pyridines (R = Et, iPr, tBu, Ph, and Me2N) by using dialkyl-tmp-zincate bases

W. Clegg, B. Conway, D.V. Graham, E. Hevia, A.R. Kennedy, R.E. Mulvey, L. Russo, D.S. Wright

Research output: Contribution to journalArticle

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Abstract

Two potassium-dialkyl-TMP-zincate bases [(pmdeta)K(mu-Et)(mu-tmp)Zn(Et)] (1) (PMDETA = N,N,N',N'',N''-pentamethyldiethylenetriamine, TMP = 2,2,6,6-tetramethylpiperidide), and [(pmdeta)K(mu-nBu)(mu-tmp)Zn(nBu)] (2), have been synthesized by a simple co-complexation procedure. Treatment of 1 with a series of substituted 4-R-pyridines (R = Me(2)N, H, Et, iPr, tBu, and Ph) gave 2-zincated products of the general formula [{2-Zn(Et)(2)-mu-4-R-C(5)H(3)N}(2)2{K(pmdeta)}] (3-8, respectively) in isolated crystalline yields of 53, 16, 7, 23, 67, and 51%, respectively; the treatment of 2 with 4-tBu-pyridine gave [{2-Zn(nBu)(2)-mu-4-tBu-C(5)H(3)N}(2)2{K(pmdeta)}] (9) in an isolated crystalline yield of 58%. Single-crystal X-ray crystallographic and NMR spectroscopic characterization of 3-9 revealed a novel structural motif consisting of a dianionic dihydroanthracene-like tricyclic ring system with a central diazadicarbadizinca (ZnCN)(2) ring, face-capped on either side by PMDETA-wrapped K(+) cations. All the new metalated pyridine complexes share this dimeric arrangement. As determined by NMR spectroscopic investigations of the reaction filtrates, those solutions producing 3, 7, 8, and 9 appear to be essentially clean reactions, in contrast to those producing 4, 5, and 6, which also contain laterally zincated coproducts. In all of these metalation reactions, the potassium-zincate base acts as an amido transfer agent with a subsequent ligand-exchange mechanism (amido replacing alkyl) inhibited by the coordinative saturation, and thus, low Lewis acidity of the 4-coordinate Zn centers in these dimeric molecules. Studies on analogous trialkyl-zincate reagents in the absence and presence of stoichiometric or substoichiometric amounts of TMP(H) established the importance of Zn-N bonds for efficient zincation.
LanguageEnglish
Pages7074-7082
Number of pages8
JournalChemistry - A European Journal
Volume15
Issue number29
DOIs
Publication statusPublished - 16 Jun 2009

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Thymidine Monophosphate
Pyridines
Potassium
Nuclear magnetic resonance
Crystalline materials
Complexation
Acidity
Cations
Single crystals
Ligands
X rays
Molecules
pyridine
diethylzinc

Keywords

  • alkali metals
  • metalation
  • potassium
  • pyridine
  • zincation

Cite this

@article{d131497b18784baf90fca5e89682948a,
title = "Structurally defined potassium-mediated zincation of pyridine and 4-R-substituted pyridines (R = Et, iPr, tBu, Ph, and Me2N) by using dialkyl-tmp-zincate bases",
abstract = "Two potassium-dialkyl-TMP-zincate bases [(pmdeta)K(mu-Et)(mu-tmp)Zn(Et)] (1) (PMDETA = N,N,N',N'',N''-pentamethyldiethylenetriamine, TMP = 2,2,6,6-tetramethylpiperidide), and [(pmdeta)K(mu-nBu)(mu-tmp)Zn(nBu)] (2), have been synthesized by a simple co-complexation procedure. Treatment of 1 with a series of substituted 4-R-pyridines (R = Me(2)N, H, Et, iPr, tBu, and Ph) gave 2-zincated products of the general formula [{2-Zn(Et)(2)-mu-4-R-C(5)H(3)N}(2)2{K(pmdeta)}] (3-8, respectively) in isolated crystalline yields of 53, 16, 7, 23, 67, and 51{\%}, respectively; the treatment of 2 with 4-tBu-pyridine gave [{2-Zn(nBu)(2)-mu-4-tBu-C(5)H(3)N}(2)2{K(pmdeta)}] (9) in an isolated crystalline yield of 58{\%}. Single-crystal X-ray crystallographic and NMR spectroscopic characterization of 3-9 revealed a novel structural motif consisting of a dianionic dihydroanthracene-like tricyclic ring system with a central diazadicarbadizinca (ZnCN)(2) ring, face-capped on either side by PMDETA-wrapped K(+) cations. All the new metalated pyridine complexes share this dimeric arrangement. As determined by NMR spectroscopic investigations of the reaction filtrates, those solutions producing 3, 7, 8, and 9 appear to be essentially clean reactions, in contrast to those producing 4, 5, and 6, which also contain laterally zincated coproducts. In all of these metalation reactions, the potassium-zincate base acts as an amido transfer agent with a subsequent ligand-exchange mechanism (amido replacing alkyl) inhibited by the coordinative saturation, and thus, low Lewis acidity of the 4-coordinate Zn centers in these dimeric molecules. Studies on analogous trialkyl-zincate reagents in the absence and presence of stoichiometric or substoichiometric amounts of TMP(H) established the importance of Zn-N bonds for efficient zincation.",
keywords = "alkali metals, metalation, potassium, pyridine, zincation",
author = "W. Clegg and B. Conway and D.V. Graham and E. Hevia and A.R. Kennedy and R.E. Mulvey and L. Russo and D.S. Wright",
year = "2009",
month = "6",
day = "16",
doi = "10.1002/chem.200900549",
language = "English",
volume = "15",
pages = "7074--7082",
journal = "Chemistry - A European Journal",
issn = "0947-6539",
number = "29",

}

Structurally defined potassium-mediated zincation of pyridine and 4-R-substituted pyridines (R = Et, iPr, tBu, Ph, and Me2N) by using dialkyl-tmp-zincate bases. / Clegg, W.; Conway, B.; Graham, D.V.; Hevia, E.; Kennedy, A.R.; Mulvey, R.E.; Russo, L.; Wright, D.S.

In: Chemistry - A European Journal, Vol. 15, No. 29, 16.06.2009, p. 7074-7082.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Structurally defined potassium-mediated zincation of pyridine and 4-R-substituted pyridines (R = Et, iPr, tBu, Ph, and Me2N) by using dialkyl-tmp-zincate bases

AU - Clegg, W.

AU - Conway, B.

AU - Graham, D.V.

AU - Hevia, E.

AU - Kennedy, A.R.

AU - Mulvey, R.E.

AU - Russo, L.

AU - Wright, D.S.

PY - 2009/6/16

Y1 - 2009/6/16

N2 - Two potassium-dialkyl-TMP-zincate bases [(pmdeta)K(mu-Et)(mu-tmp)Zn(Et)] (1) (PMDETA = N,N,N',N'',N''-pentamethyldiethylenetriamine, TMP = 2,2,6,6-tetramethylpiperidide), and [(pmdeta)K(mu-nBu)(mu-tmp)Zn(nBu)] (2), have been synthesized by a simple co-complexation procedure. Treatment of 1 with a series of substituted 4-R-pyridines (R = Me(2)N, H, Et, iPr, tBu, and Ph) gave 2-zincated products of the general formula [{2-Zn(Et)(2)-mu-4-R-C(5)H(3)N}(2)2{K(pmdeta)}] (3-8, respectively) in isolated crystalline yields of 53, 16, 7, 23, 67, and 51%, respectively; the treatment of 2 with 4-tBu-pyridine gave [{2-Zn(nBu)(2)-mu-4-tBu-C(5)H(3)N}(2)2{K(pmdeta)}] (9) in an isolated crystalline yield of 58%. Single-crystal X-ray crystallographic and NMR spectroscopic characterization of 3-9 revealed a novel structural motif consisting of a dianionic dihydroanthracene-like tricyclic ring system with a central diazadicarbadizinca (ZnCN)(2) ring, face-capped on either side by PMDETA-wrapped K(+) cations. All the new metalated pyridine complexes share this dimeric arrangement. As determined by NMR spectroscopic investigations of the reaction filtrates, those solutions producing 3, 7, 8, and 9 appear to be essentially clean reactions, in contrast to those producing 4, 5, and 6, which also contain laterally zincated coproducts. In all of these metalation reactions, the potassium-zincate base acts as an amido transfer agent with a subsequent ligand-exchange mechanism (amido replacing alkyl) inhibited by the coordinative saturation, and thus, low Lewis acidity of the 4-coordinate Zn centers in these dimeric molecules. Studies on analogous trialkyl-zincate reagents in the absence and presence of stoichiometric or substoichiometric amounts of TMP(H) established the importance of Zn-N bonds for efficient zincation.

AB - Two potassium-dialkyl-TMP-zincate bases [(pmdeta)K(mu-Et)(mu-tmp)Zn(Et)] (1) (PMDETA = N,N,N',N'',N''-pentamethyldiethylenetriamine, TMP = 2,2,6,6-tetramethylpiperidide), and [(pmdeta)K(mu-nBu)(mu-tmp)Zn(nBu)] (2), have been synthesized by a simple co-complexation procedure. Treatment of 1 with a series of substituted 4-R-pyridines (R = Me(2)N, H, Et, iPr, tBu, and Ph) gave 2-zincated products of the general formula [{2-Zn(Et)(2)-mu-4-R-C(5)H(3)N}(2)2{K(pmdeta)}] (3-8, respectively) in isolated crystalline yields of 53, 16, 7, 23, 67, and 51%, respectively; the treatment of 2 with 4-tBu-pyridine gave [{2-Zn(nBu)(2)-mu-4-tBu-C(5)H(3)N}(2)2{K(pmdeta)}] (9) in an isolated crystalline yield of 58%. Single-crystal X-ray crystallographic and NMR spectroscopic characterization of 3-9 revealed a novel structural motif consisting of a dianionic dihydroanthracene-like tricyclic ring system with a central diazadicarbadizinca (ZnCN)(2) ring, face-capped on either side by PMDETA-wrapped K(+) cations. All the new metalated pyridine complexes share this dimeric arrangement. As determined by NMR spectroscopic investigations of the reaction filtrates, those solutions producing 3, 7, 8, and 9 appear to be essentially clean reactions, in contrast to those producing 4, 5, and 6, which also contain laterally zincated coproducts. In all of these metalation reactions, the potassium-zincate base acts as an amido transfer agent with a subsequent ligand-exchange mechanism (amido replacing alkyl) inhibited by the coordinative saturation, and thus, low Lewis acidity of the 4-coordinate Zn centers in these dimeric molecules. Studies on analogous trialkyl-zincate reagents in the absence and presence of stoichiometric or substoichiometric amounts of TMP(H) established the importance of Zn-N bonds for efficient zincation.

KW - alkali metals

KW - metalation

KW - potassium

KW - pyridine

KW - zincation

UR - http://dx.doi.org/10.1002/chem.200900549

U2 - 10.1002/chem.200900549

DO - 10.1002/chem.200900549

M3 - Article

VL - 15

SP - 7074

EP - 7082

JO - Chemistry - A European Journal

T2 - Chemistry - A European Journal

JF - Chemistry - A European Journal

SN - 0947-6539

IS - 29

ER -