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Titolo:
(-)-sparteine-mediated stereoselective intramolecular carbolithiation of 4-substituted 5-hexynyl carbamates. Synthesis of enantiopure 1,3-difunctionalized alkylidene cyclopentanes
Autore:
Oestreich, M; Frohlich, R; Hoppe, D;
Indirizzi:
Univ Munster, Inst Organ Chem, D-48149 Munster, Germany Univ Munster Munster Germany D-48149 rgan Chem, D-48149 Munster, Germany
Titolo Testata:
JOURNAL OF ORGANIC CHEMISTRY
fascicolo: 23, volume: 64, anno: 1999,
pagine: 8616 - 8626
SICI:
0022-3263(19991112)64:23<8616:(SICO4>2.0.ZU;2-#
Fonte:
ISI
Lingua:
ENG
Soggetto:
ENANTIOSELECTIVE SYNTHESIS; KINETIC RESOLUTION; C-SUBSTITUTION; (-)-SPARTEINE-ASSISTED DEPROTONATION; ASYMMETRIC DEPROTONATION; TERT-BUTYLDIMETHYLSILYL; ANIONIC CYCLIZATION; PROCHIRAL KETONES; CARBANION CENTER; AMINO-ALCOHOLS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Physical, Chemical & Earth Sciences
Citazioni:
67
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:
M. Oestreich et al., "(-)-sparteine-mediated stereoselective intramolecular carbolithiation of 4-substituted 5-hexynyl carbamates. Synthesis of enantiopure 1,3-difunctionalized alkylidene cyclopentanes", J ORG CHEM, 64(23), 1999, pp. 8616-8626

Abstract

The stereoselective carbolithiation of alkynes with external chiral induction has been achieved for the first time by fusing the concepts of the asymmetric deprotonation (A) with s-BuLi/(-)-sparteine (s-BuLi/1) and the intramolecular carbolithiation (B). Several 4-functionalized 5-hexynyl carbamates with different terminal substituents have been prepared and efficiently cyclized providing enantiopure highly substituted alkylidene cyclopentanes. The presence of a sterically demanding substituent in the propargylic position is the essential feature of these cyclizations in order to suppress theabstraction of the remaining propargylic proton. Furthermore, in dependence on the terminal substituent, the 6-phenyl-substituted precursors undergo an intramolecular carbolithiation whereas for the 6-trimethylsilyl-substituted alkynes a sub sequent migration of the O-carbamoyl group onto the vinylic carbanionic center follows.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 29/11/20 alle ore 06:50:31