Abstract
| Language | English |
|---|---|
| Pages | 2375-2384 |
| Number of pages | 10 |
| Journal | Journal of the American Chemical Society |
| Volume | 131 |
| Issue number | 6 |
| DOIs | |
| Publication status | Published - 26 Jan 2009 |
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Keywords
- spectroscopy
- crystallography
- solvent effects
- mollecular structures
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Closer insight into the reactivity of TMP-dialkyl zincates in directed ortho-zincation of anisole : experimental evidence of amido basicity and structural elucidation of key reaction intermediates. / Clegg, W.; Conway, B.; Hevia, E.; McCall, M.D.; Russo, L.; Mulvey, R.E.
In: Journal of the American Chemical Society, Vol. 131, No. 6, 26.01.2009, p. 2375-2384.Research output: Contribution to journal › Article
TY - JOUR
T1 - Closer insight into the reactivity of TMP-dialkyl zincates in directed ortho-zincation of anisole
T2 - Journal of the American Chemical Society
AU - Clegg, W.
AU - Conway, B.
AU - Hevia, E.
AU - McCall, M.D.
AU - Russo, L.
AU - Mulvey, R.E.
PY - 2009/1/26
Y1 - 2009/1/26
N2 - The new dialkyl(aryl) lithium zincates [(THF)2Li(C6H4−OMe)MeZnMe] (4), [(TMEDA)Li(C6H4−OMe)MeZnMe] (6), [(THF)3Li(C6H4−OMe)tBuZntBu] (7), and [(PMDETA)Li(C6H4−OMe)tBuZntBu] (8) have been prepared by co-complexation reactions of lithiated anisole with the relevant dialkylzinc compound and the relevant Lewis base. These new heterobimetallic compounds have been characterized in solution using 1H, 13C{H}, and 7Li NMR spectroscopy, and the molecular structures of 6 and 8 have been elucidated by X-ray crystallography. In 6 the distinct metals are connected through the anisole ligand which binds in an ambidentate fashion (through carbon−zinc and oxygen−lithium contacts) and also through one of the methyl groups, to close a [LiOCCZnC] six-membered ring; whereas 8 displays an open structure where anisole connects the two metals (in the same mode as in 6) but with the tert-butyl groups exclusively bonded terminally to zinc. Reactivity studies of zincates 4 and 7 with the amine TMP(H) supply experimental evidence that these heterobimetallic compounds are intermediates in the two-step deprotonation reaction of anisole by TMP−dialkyl zincates and show the relevance of the alkyl groups in the efficiency of TMP−dialkyl zincate bases. In addition, important solvent effects have also been evaluated. When hexane is added to THF solutions of compounds 4 or 7, the homoleptic tetraorganozincate [(THF)2Li2Zn(C6H4−OMe)4] (5) is obtained as the result of a disproportionation process. This lithium-rich zincate has also been spectroscopically and crystallographically characterized.
AB - The new dialkyl(aryl) lithium zincates [(THF)2Li(C6H4−OMe)MeZnMe] (4), [(TMEDA)Li(C6H4−OMe)MeZnMe] (6), [(THF)3Li(C6H4−OMe)tBuZntBu] (7), and [(PMDETA)Li(C6H4−OMe)tBuZntBu] (8) have been prepared by co-complexation reactions of lithiated anisole with the relevant dialkylzinc compound and the relevant Lewis base. These new heterobimetallic compounds have been characterized in solution using 1H, 13C{H}, and 7Li NMR spectroscopy, and the molecular structures of 6 and 8 have been elucidated by X-ray crystallography. In 6 the distinct metals are connected through the anisole ligand which binds in an ambidentate fashion (through carbon−zinc and oxygen−lithium contacts) and also through one of the methyl groups, to close a [LiOCCZnC] six-membered ring; whereas 8 displays an open structure where anisole connects the two metals (in the same mode as in 6) but with the tert-butyl groups exclusively bonded terminally to zinc. Reactivity studies of zincates 4 and 7 with the amine TMP(H) supply experimental evidence that these heterobimetallic compounds are intermediates in the two-step deprotonation reaction of anisole by TMP−dialkyl zincates and show the relevance of the alkyl groups in the efficiency of TMP−dialkyl zincate bases. In addition, important solvent effects have also been evaluated. When hexane is added to THF solutions of compounds 4 or 7, the homoleptic tetraorganozincate [(THF)2Li2Zn(C6H4−OMe)4] (5) is obtained as the result of a disproportionation process. This lithium-rich zincate has also been spectroscopically and crystallographically characterized.
KW - spectroscopy
KW - crystallography
KW - solvent effects
KW - mollecular structures
U2 - 10.1021/ja8087168
DO - 10.1021/ja8087168
M3 - Article
VL - 131
SP - 2375
EP - 2384
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 6
ER -