Base Catalyzed Dimerization of (o-Formyl-Z-Hydroxyacetophenones

Abstract

bstract: Refluxing w-formyl-2-hydroxyacetophenones in ethanol containing triethylamine as basic catalyst produced the dimerized product identified as 2-(2- hydroxyary|)-4H,5H-pyrano[2,3-b]chromen-5-ones 2. Meanwhile, heating w-formyl-Zhydroxyacetophenones in aqueous sodium hydroxide solution afforded another type of dimeric product identified as 3-[2-(2-hydroxy-5-substituted benzoyl)vinyl]—6- substituted-4H-chromen-4-ones 3. The proposed mechanisms were discussed. The mode of dimerization of w-formyl-Z-hydroxyacetophenones depends on the type of catalyst used and the reaction conditions. Structures of the synthesized compounds were deduced on the basis of their analytical and spectral data.