A formal [3 + 3] cycloaddition reaction. Improved reactivity using alpha,beta-unsaturated iminium salts and evidence for reversibility of 6pi-electron electrocyclic ring closure of 1-oxatrienes.
J Org Chem
; 68(5): 1729-35, 2003 Mar 07.
Article
in En
| MEDLINE
| ID: mdl-12608785
ABSTRACT
A detailed account regarding a formal [3 + 3] cycloaddition method using 4-hydroxy-2-pyrones and 1,3-diketones is described here. This formal cycloaddition reaction or annulation reaction is synthetically useful for constructing 2H-pyranyl heterocycles. The usage of alpha,beta-unsaturated iminium salts is significant in controlling competing reaction pathways to give exclusively 2H-pyrans. Most significantly, experimental evidence is provided to support the mechanism of this reaction that involves a sequential Knoevenagel condensation and a reversible 6pi-electron electrocyclic ring-closure of 1-oxatrienes.
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Collection:
01-internacional
Database:
MEDLINE
Main subject:
Pyrans
/
Pyrones
/
Chemistry, Organic
/
Ketones
Language:
En
Journal:
J Org Chem
Year:
2003
Document type:
Article
Affiliation country:
United States