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Keywords
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Multi-component reaction, Tetrahydrobenzopyrans, 3,4-Dihydropyrano[c]Chromenes, Green
solvent; Heterogeneous catalyst, Ionic liquid.
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Abstract
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Polyaniline, polyaniline/SiO2 and poly(4-vinylpyridine) are highly effective base catalysts for the
synthesis of tetrahydrobenzo[b]pyran and 3,4-dihydropyrano[c]chromene derivatives by one-pot three-component
condensation reaction of aryl aldehydes, malononitrile and α-hydroxy or α-amino activated C–H acids such as
1,3-cyclohexanedione, dimedone, 4-hydroxy-6-methylpyrone, 4-hydroxycoumarin, 1,3-dimethylbarbituric acid
and 1,3-dimethyl-6-amino uracil. The remarkable advantages of this new procedure are high yields, short
experimental time, mild reaction condition, low cast and easy preparation of the catalysts and no need for any
workup and purification after comletion of the reaction. In addition, these catalysts exhibited excellent
recoverability without negligible decrease of their activities after at least six cycles of reaction
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