Aldol condensation of piperonal (I) with 4-methoxyacetophenone (II) afforded chalcone (III). Subsequent addition of KCN to (III) in the presence of AcOH gave nitrile (IV), which was hydrolyzed in methanol in the presence of p-TsOH to provide ketoester (V). Subsequent base-catalyzed condensation of (V) with aldehyde (VI), followed by cyclization in refluxing AcOH furnished the target butenolide.