Synthetic and structural insights into the zincation of toluene: direct synergic ring metallation versus indirect nonsynergic lateral metallation

D.R. Armstrong, J. Garcia-Alvarez, D.V. Graham, G.W. Honeyman, E. Hevia, A.R. Kennedy, R.E. Mulvey

Research output: Contribution to journalArticle

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Abstract

Toluene has been directly zincated by reaction with the heteroleptic sodium zincate [(tmeda)NaACHTUNGTRENUNG(tBu)- ACHTUNGTRENUNG(tmp)ZnACHTUNGTRENUNG(tBu)] (1) to afford a statistical mixture of the meta and para regioisomers of [(tmeda)NaACHTUNGTRENUNG(C6H4Me)- ACHTUNGTRENUNG(tmp)ZnACHTUNGTRENUNG(tBu)] (2) (TMEDA= N,N,N',N'-tetramethylethylenediamine, TMP=2,2,6,6-tetramethylpiperidide). Interestingly, the methyl group of toluene has been left untouched by the mixed-metal base. The crystal structures of both regioisomers have been elucidated by using X-ray crystallography, which revealed a common motif, in which zinc lies in the same plane as the tolyl ring and binds strongly to the carbon that has experienced the deprotonation, leading to a covalent s bond; whereas sodium adopts a perpendicular disposition, p-engaging with the aromatic ring. DFT studies of the reaction of 1 with toluene showed that of the four possible regioisomers, the experimentally observed meta and para ones are the most thermodynamically preferred products due to a large extent to the combined (synergic) effect of the zinc and sodium and the different way in which each metal binds to the tolyl anion. In contrast, the more straightforward benzyl-based zincate [(tmeda)2NaACHTUNGTRENUNG(CH2Ph)ZnACHTUNGTRENUNG(tBu)2] (3) is obtained through an indirect route, in which toluene is first laterally metallated by monometallic butylsodium to afford benzylsodium, which then forms a mixed-metal compound by co-complexation with tBu2Zn. Zincate 3 has been characterised by X-ray crystallography in the solid state and by NMR spectroscopy in deuterated THF solution.
LanguageEnglish
Pages3800-3807
Number of pages7
JournalChemistry - A European Journal
Volume15
Issue number15
DOIs
Publication statusPublished - 2009

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Toluene
Metals
Sodium
Thymidine Monophosphate
Deprotonation
Covalent bonds
X ray crystallography
Discrete Fourier transforms
Zinc
X rays
Crystals

Keywords

  • alkali metals
  • metallation
  • synergic chemistry
  • zincates

Cite this

@article{66c61370f5d947d6851a7ad0d555a75d,
title = "Synthetic and structural insights into the zincation of toluene: direct synergic ring metallation versus indirect nonsynergic lateral metallation",
abstract = "Toluene has been directly zincated by reaction with the heteroleptic sodium zincate [(tmeda)NaACHTUNGTRENUNG(tBu)- ACHTUNGTRENUNG(tmp)ZnACHTUNGTRENUNG(tBu)] (1) to afford a statistical mixture of the meta and para regioisomers of [(tmeda)NaACHTUNGTRENUNG(C6H4Me)- ACHTUNGTRENUNG(tmp)ZnACHTUNGTRENUNG(tBu)] (2) (TMEDA= N,N,N',N'-tetramethylethylenediamine, TMP=2,2,6,6-tetramethylpiperidide). Interestingly, the methyl group of toluene has been left untouched by the mixed-metal base. The crystal structures of both regioisomers have been elucidated by using X-ray crystallography, which revealed a common motif, in which zinc lies in the same plane as the tolyl ring and binds strongly to the carbon that has experienced the deprotonation, leading to a covalent s bond; whereas sodium adopts a perpendicular disposition, p-engaging with the aromatic ring. DFT studies of the reaction of 1 with toluene showed that of the four possible regioisomers, the experimentally observed meta and para ones are the most thermodynamically preferred products due to a large extent to the combined (synergic) effect of the zinc and sodium and the different way in which each metal binds to the tolyl anion. In contrast, the more straightforward benzyl-based zincate [(tmeda)2NaACHTUNGTRENUNG(CH2Ph)ZnACHTUNGTRENUNG(tBu)2] (3) is obtained through an indirect route, in which toluene is first laterally metallated by monometallic butylsodium to afford benzylsodium, which then forms a mixed-metal compound by co-complexation with tBu2Zn. Zincate 3 has been characterised by X-ray crystallography in the solid state and by NMR spectroscopy in deuterated THF solution.",
keywords = "alkali metals, metallation, synergic chemistry, zincates",
author = "D.R. Armstrong and J. Garcia-Alvarez and D.V. Graham and G.W. Honeyman and E. Hevia and A.R. Kennedy and R.E. Mulvey",
year = "2009",
doi = "10.1002/chem.200801928",
language = "English",
volume = "15",
pages = "3800--3807",
journal = "Chemistry - A European Journal",
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Synthetic and structural insights into the zincation of toluene: direct synergic ring metallation versus indirect nonsynergic lateral metallation. / Armstrong, D.R.; Garcia-Alvarez, J.; Graham, D.V.; Honeyman, G.W.; Hevia, E.; Kennedy, A.R.; Mulvey, R.E.

In: Chemistry - A European Journal, Vol. 15, No. 15, 2009, p. 3800-3807.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Synthetic and structural insights into the zincation of toluene: direct synergic ring metallation versus indirect nonsynergic lateral metallation

AU - Armstrong, D.R.

AU - Garcia-Alvarez, J.

AU - Graham, D.V.

AU - Honeyman, G.W.

AU - Hevia, E.

AU - Kennedy, A.R.

AU - Mulvey, R.E.

PY - 2009

Y1 - 2009

N2 - Toluene has been directly zincated by reaction with the heteroleptic sodium zincate [(tmeda)NaACHTUNGTRENUNG(tBu)- ACHTUNGTRENUNG(tmp)ZnACHTUNGTRENUNG(tBu)] (1) to afford a statistical mixture of the meta and para regioisomers of [(tmeda)NaACHTUNGTRENUNG(C6H4Me)- ACHTUNGTRENUNG(tmp)ZnACHTUNGTRENUNG(tBu)] (2) (TMEDA= N,N,N',N'-tetramethylethylenediamine, TMP=2,2,6,6-tetramethylpiperidide). Interestingly, the methyl group of toluene has been left untouched by the mixed-metal base. The crystal structures of both regioisomers have been elucidated by using X-ray crystallography, which revealed a common motif, in which zinc lies in the same plane as the tolyl ring and binds strongly to the carbon that has experienced the deprotonation, leading to a covalent s bond; whereas sodium adopts a perpendicular disposition, p-engaging with the aromatic ring. DFT studies of the reaction of 1 with toluene showed that of the four possible regioisomers, the experimentally observed meta and para ones are the most thermodynamically preferred products due to a large extent to the combined (synergic) effect of the zinc and sodium and the different way in which each metal binds to the tolyl anion. In contrast, the more straightforward benzyl-based zincate [(tmeda)2NaACHTUNGTRENUNG(CH2Ph)ZnACHTUNGTRENUNG(tBu)2] (3) is obtained through an indirect route, in which toluene is first laterally metallated by monometallic butylsodium to afford benzylsodium, which then forms a mixed-metal compound by co-complexation with tBu2Zn. Zincate 3 has been characterised by X-ray crystallography in the solid state and by NMR spectroscopy in deuterated THF solution.

AB - Toluene has been directly zincated by reaction with the heteroleptic sodium zincate [(tmeda)NaACHTUNGTRENUNG(tBu)- ACHTUNGTRENUNG(tmp)ZnACHTUNGTRENUNG(tBu)] (1) to afford a statistical mixture of the meta and para regioisomers of [(tmeda)NaACHTUNGTRENUNG(C6H4Me)- ACHTUNGTRENUNG(tmp)ZnACHTUNGTRENUNG(tBu)] (2) (TMEDA= N,N,N',N'-tetramethylethylenediamine, TMP=2,2,6,6-tetramethylpiperidide). Interestingly, the methyl group of toluene has been left untouched by the mixed-metal base. The crystal structures of both regioisomers have been elucidated by using X-ray crystallography, which revealed a common motif, in which zinc lies in the same plane as the tolyl ring and binds strongly to the carbon that has experienced the deprotonation, leading to a covalent s bond; whereas sodium adopts a perpendicular disposition, p-engaging with the aromatic ring. DFT studies of the reaction of 1 with toluene showed that of the four possible regioisomers, the experimentally observed meta and para ones are the most thermodynamically preferred products due to a large extent to the combined (synergic) effect of the zinc and sodium and the different way in which each metal binds to the tolyl anion. In contrast, the more straightforward benzyl-based zincate [(tmeda)2NaACHTUNGTRENUNG(CH2Ph)ZnACHTUNGTRENUNG(tBu)2] (3) is obtained through an indirect route, in which toluene is first laterally metallated by monometallic butylsodium to afford benzylsodium, which then forms a mixed-metal compound by co-complexation with tBu2Zn. Zincate 3 has been characterised by X-ray crystallography in the solid state and by NMR spectroscopy in deuterated THF solution.

KW - alkali metals

KW - metallation

KW - synergic chemistry

KW - zincates

UR - http://dx.doi.org/10.1002/chem.200801928

U2 - 10.1002/chem.200801928

DO - 10.1002/chem.200801928

M3 - Article

VL - 15

SP - 3800

EP - 3807

JO - Chemistry - A European Journal

T2 - Chemistry - A European Journal

JF - Chemistry - A European Journal

SN - 0947-6539

IS - 15

ER -