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Titolo:
Experimental and theoretical investigations of lithio-indenyl carbamate/(-)-sparteine and (-)-alpha-isosparteine complexes
Autore:
Heinl, T; Retzow, S; Hoppe, D; Fraenkel, G; Chow, A;
Indirizzi:
Univ Munster, Inst Organ Chem, D-48149 Munster, Germany Univ Munster Munster Germany D-48149 rgan Chem, D-48149 Munster, Germany Ohio State Univ, Dept Chem, Columbus, OH 43210 USA Ohio State Univ Columbus OH USA 43210 , Dept Chem, Columbus, OH 43210 USA
Titolo Testata:
CHEMISTRY-A EUROPEAN JOURNAL
fascicolo: 12, volume: 5, anno: 1999,
pagine: 3464 - 3470
SICI:
0947-6539(199912)5:12<3464:EATIOL>2.0.ZU;2-5
Fonte:
ISI
Lingua:
ENG
Soggetto:
ENANTIOSELECTIVE SYNTHESES; HOMOALDOL REACTION; ASYMMETRIC DEPROTONATIONS; ORGANIC-SYNTHESIS; (-)-SPARTEINE; LITHIATION; SUBSTITUTION; PHEROMONE; PATHWAYS;
Keywords:
chiral carbanions; line shape analysis; lithiation; semi-empirical calculations; (-)-sparteine;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
40
Recensione:
Indirizzi per estratti:
Indirizzo: Hoppe, D Univ Munster, Inst Organ Chem, Corrensstr 40, D-48149 Munster, Germany Univ Munster Corrensstr 40 Munster Germany D-48149 ster, Germany
Citazione:
T. Heinl et al., "Experimental and theoretical investigations of lithio-indenyl carbamate/(-)-sparteine and (-)-alpha-isosparteine complexes", CHEM-EUR J, 5(12), 1999, pp. 3464-3470

Abstract

1-Carbamoyloxy-1-lithio-indene complexes of (-)-sparteine and (-)-alpha-isosparteine 5/epi-5 and 6/epi-6 were prepared and found to be configurationally unstable on the macroscopic time scale. Ratios of epimers and the ratesof interconversion, including some activation parameters, were determined by temperature-dependent line shape analysis in the H-1 NMR spectrum. The highest barrier for interconversion (Delta Delta H-not equal > 25 kcal mol(-1)) was recorded for the 2-methylindenide/(-)-sparteine complexes 5b/epi-5b, whereas the activation energy for the epimerisation of the indenide/(-)-a-isosparteine complex 6a/epi-6a is too low to be recorded by this method. Trapping of the lithium compounds 5/epi-5 and 6/epi-6 proceeds with methyl iodide in an anti-S-E' process. The obtained enantiomeric ratios correlate roughly with the observed epimeric ratios in the lithium intermediates. The absolute configurations of the methylation products 7c and 7d have been established by chemical correlation with the known (+)-(S)3-methyl-1H-indan-1-one. The ratios correspond well to those predicted by semiempirical PM3 calculations on the relative stability of the diastereomeric complexes.

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Documento generato il 23/01/20 alle ore 18:22:33