Metalation of 2,4,6-trimethylacetophenone using organozinc reagents: the role of the base in determining composition and structure of the developing enolate

D.R. Armstrong, A.M. Drummond, L. Balloch, D.V. Graham, E. Hevia, A.R. Kennedy

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

The new mixed lithium−zinc enolate compounds [(TMEDA)2Li2Zn{OC(CH2)Mes}4] (2) and [{TMP(H)}2Li2Zn{OC(CH2)Mes}4] (3) were prepared by reaction of the sterically demanding ketone 2,4,6-trimethylacetophenone (1) with the all-amido homoleptic zincate [LiZn(TMP)3] (TMP = 2,2,6,6-tetramethylpiperidide). X-ray crystallographic studies revealed that these compounds adopt a trinuclear Li···Zn···Li chain arrangement with enolate O bridges. In contrast, the metalation of 1 with heteroleptic [(TMEDA)LiZn(TMP)Me2] afforded the dimeric lithium enolate [(TMEDA)2Li2{OC(CH2)Mes}2] (4) as a crystalline solid, which has been characterized in the solid state by X-ray crystallography, and Me2Zn·TMEDA and TMP(H) as coproducts, showing that the dimethylamido zincate behaves as an amide base. The homoleptic zinc enolate [(TMEDA)Zn{OC(CH2)Mes}2] (5) was obtained by reaction of 1 with the zinc amide Zn(TMP)2, and its structure was determined by X-ray crystallography. 5 adopts a rarely observed monomeric arrangement where the two enolate groups bind terminally to the zinc. New enolates 2−5 have also been characterized by 1H, 13C, and 7Li NMR spectroscopy in C6D6 solution. DFT studies of the metalation of 1 by Zn(TMP)2 and Et2Zn revealed that the former amide has a much greater kinetic basicity than the latter alkyl reagent. Copyright © 2010 American Chemical Society
Original languageEnglish
Pages (from-to)5860-5866
Number of pages6
JournalOrganometallics
Volume27
Issue number22
DOIs
Publication statusPublished - 24 Nov 2008

Fingerprint

Thymidine Monophosphate
amides
reagents
zinc
crystallography
Amides
Zinc
Chemical analysis
X ray crystallography
x rays
ketones
lithium
solid state
Alkalinity
nuclear magnetic resonance
Ketones
Lithium
Discrete Fourier transforms
Nuclear magnetic resonance spectroscopy
kinetics

Keywords

  • metalation
  • 2
  • 4
  • 6-trimethylacetophenone
  • organozinc reagents
  • role
  • base
  • composition
  • structure
  • developing enolate

Cite this

@article{5b6de9b4ac024c02acc3fe4b540cce78,
title = "Metalation of 2,4,6-trimethylacetophenone using organozinc reagents: the role of the base in determining composition and structure of the developing enolate",
abstract = "The new mixed lithium−zinc enolate compounds [(TMEDA)2Li2Zn{OC(CH2)Mes}4] (2) and [{TMP(H)}2Li2Zn{OC(CH2)Mes}4] (3) were prepared by reaction of the sterically demanding ketone 2,4,6-trimethylacetophenone (1) with the all-amido homoleptic zincate [LiZn(TMP)3] (TMP = 2,2,6,6-tetramethylpiperidide). X-ray crystallographic studies revealed that these compounds adopt a trinuclear Li···Zn···Li chain arrangement with enolate O bridges. In contrast, the metalation of 1 with heteroleptic [(TMEDA)LiZn(TMP)Me2] afforded the dimeric lithium enolate [(TMEDA)2Li2{OC(CH2)Mes}2] (4) as a crystalline solid, which has been characterized in the solid state by X-ray crystallography, and Me2Zn·TMEDA and TMP(H) as coproducts, showing that the dimethylamido zincate behaves as an amide base. The homoleptic zinc enolate [(TMEDA)Zn{OC(CH2)Mes}2] (5) was obtained by reaction of 1 with the zinc amide Zn(TMP)2, and its structure was determined by X-ray crystallography. 5 adopts a rarely observed monomeric arrangement where the two enolate groups bind terminally to the zinc. New enolates 2−5 have also been characterized by 1H, 13C, and 7Li NMR spectroscopy in C6D6 solution. DFT studies of the metalation of 1 by Zn(TMP)2 and Et2Zn revealed that the former amide has a much greater kinetic basicity than the latter alkyl reagent. Copyright {\circledC} 2010 American Chemical Society",
keywords = "metalation, 2, 4, 6-trimethylacetophenone, organozinc reagents, role, base, composition, structure, developing enolate",
author = "D.R. Armstrong and A.M. Drummond and L. Balloch and D.V. Graham and E. Hevia and A.R. Kennedy",
note = "http://suprimo.lib.strath.ac.uk/primo_library/libweb/action/search.do?ct=facet&fctN=facet_fmt&fctV=include+only+journals+or+serials&frbg=&dum=true&vid=SUVU01&vl(54032236UI0)=lsr02&vl(96071691UI1)=all_items&srt=rank&indx=1&dstmp=1270123144070&tab=local&ct=search&scp.scps=scope{\%}3A(SU)&vl(freeText0)=Organometallics&fn=search&mode=Basic&dscnt=0 ; Abstract taken from http://pubs.acs.org/doi/abs/10.1021/om800658s",
year = "2008",
month = "11",
day = "24",
doi = "10.1021/om800658s",
language = "English",
volume = "27",
pages = "5860--5866",
journal = "Organometallics",
issn = "0276-7333",
publisher = "American Chemical Society",
number = "22",

}

Metalation of 2,4,6-trimethylacetophenone using organozinc reagents: the role of the base in determining composition and structure of the developing enolate. / Armstrong, D.R.; Drummond, A.M.; Balloch, L.; Graham, D.V.; Hevia, E.; Kennedy, A.R.

In: Organometallics, Vol. 27, No. 22, 24.11.2008, p. 5860-5866.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Metalation of 2,4,6-trimethylacetophenone using organozinc reagents: the role of the base in determining composition and structure of the developing enolate

AU - Armstrong, D.R.

AU - Drummond, A.M.

AU - Balloch, L.

AU - Graham, D.V.

AU - Hevia, E.

AU - Kennedy, A.R.

N1 - http://suprimo.lib.strath.ac.uk/primo_library/libweb/action/search.do?ct=facet&fctN=facet_fmt&fctV=include+only+journals+or+serials&frbg=&dum=true&vid=SUVU01&vl(54032236UI0)=lsr02&vl(96071691UI1)=all_items&srt=rank&indx=1&dstmp=1270123144070&tab=local&ct=search&scp.scps=scope%3A(SU)&vl(freeText0)=Organometallics&fn=search&mode=Basic&dscnt=0 ; Abstract taken from http://pubs.acs.org/doi/abs/10.1021/om800658s

PY - 2008/11/24

Y1 - 2008/11/24

N2 - The new mixed lithium−zinc enolate compounds [(TMEDA)2Li2Zn{OC(CH2)Mes}4] (2) and [{TMP(H)}2Li2Zn{OC(CH2)Mes}4] (3) were prepared by reaction of the sterically demanding ketone 2,4,6-trimethylacetophenone (1) with the all-amido homoleptic zincate [LiZn(TMP)3] (TMP = 2,2,6,6-tetramethylpiperidide). X-ray crystallographic studies revealed that these compounds adopt a trinuclear Li···Zn···Li chain arrangement with enolate O bridges. In contrast, the metalation of 1 with heteroleptic [(TMEDA)LiZn(TMP)Me2] afforded the dimeric lithium enolate [(TMEDA)2Li2{OC(CH2)Mes}2] (4) as a crystalline solid, which has been characterized in the solid state by X-ray crystallography, and Me2Zn·TMEDA and TMP(H) as coproducts, showing that the dimethylamido zincate behaves as an amide base. The homoleptic zinc enolate [(TMEDA)Zn{OC(CH2)Mes}2] (5) was obtained by reaction of 1 with the zinc amide Zn(TMP)2, and its structure was determined by X-ray crystallography. 5 adopts a rarely observed monomeric arrangement where the two enolate groups bind terminally to the zinc. New enolates 2−5 have also been characterized by 1H, 13C, and 7Li NMR spectroscopy in C6D6 solution. DFT studies of the metalation of 1 by Zn(TMP)2 and Et2Zn revealed that the former amide has a much greater kinetic basicity than the latter alkyl reagent. Copyright © 2010 American Chemical Society

AB - The new mixed lithium−zinc enolate compounds [(TMEDA)2Li2Zn{OC(CH2)Mes}4] (2) and [{TMP(H)}2Li2Zn{OC(CH2)Mes}4] (3) were prepared by reaction of the sterically demanding ketone 2,4,6-trimethylacetophenone (1) with the all-amido homoleptic zincate [LiZn(TMP)3] (TMP = 2,2,6,6-tetramethylpiperidide). X-ray crystallographic studies revealed that these compounds adopt a trinuclear Li···Zn···Li chain arrangement with enolate O bridges. In contrast, the metalation of 1 with heteroleptic [(TMEDA)LiZn(TMP)Me2] afforded the dimeric lithium enolate [(TMEDA)2Li2{OC(CH2)Mes}2] (4) as a crystalline solid, which has been characterized in the solid state by X-ray crystallography, and Me2Zn·TMEDA and TMP(H) as coproducts, showing that the dimethylamido zincate behaves as an amide base. The homoleptic zinc enolate [(TMEDA)Zn{OC(CH2)Mes}2] (5) was obtained by reaction of 1 with the zinc amide Zn(TMP)2, and its structure was determined by X-ray crystallography. 5 adopts a rarely observed monomeric arrangement where the two enolate groups bind terminally to the zinc. New enolates 2−5 have also been characterized by 1H, 13C, and 7Li NMR spectroscopy in C6D6 solution. DFT studies of the metalation of 1 by Zn(TMP)2 and Et2Zn revealed that the former amide has a much greater kinetic basicity than the latter alkyl reagent. Copyright © 2010 American Chemical Society

KW - metalation

KW - 2

KW - 4

KW - 6-trimethylacetophenone

KW - organozinc reagents

KW - role

KW - base

KW - composition

KW - structure

KW - developing enolate

UR - http://dx.doi.org/10.1021/om800658s

U2 - 10.1021/om800658s

DO - 10.1021/om800658s

M3 - Article

VL - 27

SP - 5860

EP - 5866

JO - Organometallics

JF - Organometallics

SN - 0276-7333

IS - 22

ER -