The base catalyzed reaction of diethyl 1,3-acetonedicarboxylate with 2-hydroxybenzylidineindenediones was studied. The reaction provides a facile and expeditious protocol for the synthesis of natural product-inspired fluorenone-fused coumarins in good to very good yields. This process resembles a combination of domino Michael /intramolecular Knovenagel /aromatization /lactonization reactions in a single step. Although this reaction operates with many bases, the best yields were obtained with DMAP as a catalyst. This protocol could open new potential avenues for the synthesis of fused coumarins by the reaction of substituted β-ketoesters with different 2-(2-hydroxybenzylidene) of 1,3-dicarbonyl compounds.
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