Mechanistic insight into the acid-catalyzed isomerization of biomass-derived polysubstituted pyrrolidines: an experimental and DFT study.
Org Biomol Chem
; 15(2): 426-434, 2017 Jan 04.
Article
en En
| MEDLINE
| ID: mdl-27924326
ABSTRACT
The 1,3-dipolar cycloaddition reactions of azomethine ylides is one of the preferred methods for the synthesis of polysubstituted pyrrolidines. The use of chiral dipolarophiles derived from carbohydrates yields enantiomerically pure pyrrolidines, usually in good to excellent endo selectivities, along with other minor stereoisomers. Recently, we found an unusual isomerization event that allowed the isolation of useful pyrrolidines with relative stereochemistries difficult to obtain otherwise. Although a simple and efficient protocol to promote these transformations was developed, the mechanism was not fully unravelled. Herein, after a combination of experimental, spectroscopic and computational studies (using DFT methods) we propose that this isomerization event takes place through a retro-Mannich//Mannich cascade, via the formation of an iminium ion with E geometry.
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1
Colección:
01-internacional
Base de datos:
MEDLINE
Idioma:
En
Revista:
Org Biomol Chem
Asunto de la revista:
BIOQUIMICA
/
QUIMICA
Año:
2017
Tipo del documento:
Article
País de afiliación:
Argentina
Pais de publicación:
ENGLAND
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ESCOCIA
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GB
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GREAT BRITAIN
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INGLATERRA
/
REINO UNIDO
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SCOTLAND
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UK
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UNITED KINGDOM