[3+2] versus [4+2] cycloadditions of quinone monoimide with azadienes: a Lewis acid-free access to 5-amino-2,3-dihydrobenzofuranes.
The reaction between p-quinone monoimide 1a and various azadienes 2 is described in the absence of a Lewis acid promoter. When alpha,beta-unsaturated hydrazones are substituted by proton or alkyl groups, 2,3-dihydrobenzofuranes 4, a motif that is present in numerous biologically active products, are obtained in moderate to excellent yields. The regio- and stereoselectivity of this reaction has been proved by a complete NMR study, including 1H-15N correlations.
Lomberget
Thierry
T
Laboratoire de Chimie Thérapeutique, EA 3741, Ecosystèmes et Molécules Bioactives, Faculté de Pharmacie, Université Claude Bernard Lyon 1, 8 Avenue Rockefeller, 69373 Lyon Cedex 08, France.
Baragona
Fabien
F
Fenet
Bernard
B
Barret
Roland
R