Abstract
Reaction of 4-hydroxy-6-methyl-2-pyrone (1a) as well as 4-hydroxy-6-methyl-2(1H)-pyridones (1b-d) with arylmethylene malononitriles or arylmethylene methyl cyanoacetates (2a-h) leads to the formation of the very stable 5,6-fused bicyclic 2-amino-4Hpyran derivatives 3a-3af.
Highlights
Wiener et al first published [1] that 4-hydroxycoumarin cyclized through Michael addition to benzylidene malononitrile in pyridine as solvent to give a derivative of 2-aminopyrano[3,2-c]benzopyran (A) (Figure 1)
Junek and Aigner [2] found a second case of this heterocyclization via addition of 4-hydroxy-6-methyl-2-pyrone (1a, “triacetic acid lactone”, Scheme 1) to tetracyanoethylene, preparing a substituted 2-amino-4H,5H-pyrano[4,3-b]pyran (B)
Beside 4hydroxy-6-methyl-2(1H)-pyridone (1b), its N-substituted derivatives 1c,d were successfully employed in the reaction
Summary
Wiener et al first published [1] that 4-hydroxycoumarin cyclized through Michael addition to benzylidene malononitrile in pyridine as solvent to give a derivative of 2-aminopyrano[3,2-c]benzopyran (A) (Figure 1).
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