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Titolo:
PRACTICAL SYNTHESIS OF SPIROCYCLIC BIS-C,C-GLYCOSIDES - MECHANISTIC MODELS IN EXPLANATION OF REARRANGEMENT STEREOSELECTIVITY AND THE BIFURCATION OF REACTION PATHWAYS
Autore:
PAQUETTE LA; KINNEY MJ; DULLWEBER U;
Indirizzi:
OHIO STATE UNIV,EVANS CHEM LABS COLUMBUS OH 43210
Titolo Testata:
Journal of organic chemistry
fascicolo: 6, volume: 62, anno: 1997,
pagine: 1713 - 1722
SICI:
0022-3263(1997)62:6<1713:PSOSB->2.0.ZU;2-A
Fonte:
ISI
Lingua:
ENG
Soggetto:
FERRIER REARRANGEMENT; C-GLYCOSIDES; STEREOCONTROLLED SYNTHESIS; GLYCOSYLIDENE CARBENES; POLARITY INVERSION; PENTENYL ESTERS; ANOMERIC CENTER; GLYCALS; ROUTE; SILYLACETYLENES;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
58
Recensione:
Indirizzi per estratti:
Citazione:
L.A. Paquette et al., "PRACTICAL SYNTHESIS OF SPIROCYCLIC BIS-C,C-GLYCOSIDES - MECHANISTIC MODELS IN EXPLANATION OF REARRANGEMENT STEREOSELECTIVITY AND THE BIFURCATION OF REACTION PATHWAYS", Journal of organic chemistry, 62(6), 1997, pp. 1713-1722

Abstract

The susceptibility of glycal-derived carbinols to acid-catalyzed ringexpansion is described. In the systems prepared from cyclopentanone, Ferrier ionization precedes the pinacol-like Wagner-Meerwein shift, thermodynamic control operates, and high stereoselectivity is seen if a C(6) substituent is present. In contrast, the adducts to cyclobutanoneexhibit release of ring strain under kinetically controlled conditions and intercept the oxonium species reversibly formed via direct proton transfer. The results show that the substituents positioned on the glycal ring have a pronounced influence on whether a chair-like or twist-boat transition state geometry is adopted primarily. The composite reaction profiles reveal for the first time the fundamental importance of exothermicity and of substitution in these spiro glycosidation reactions. Since optical activity is preserved in all instances, the utility of this chemistry for the synthesis of bis-C,C-glycosides and more complex oxacyclics appears promising.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 27/09/20 alle ore 00:46:45