Condensations at the 6 Position of the Methyl Ester and the Dimethylamide of 3,5-Dioxohexanoic Acid via 2,4,6-Trianions

Article abstract of DOI:10.1021/jo00325a026

The trianions of methyl 3,5-dioxohexanoate and N,N-dimethyl-3,5-dioxohexanamide have been prepared by treatment of the compounds first with NaH to form the monoanions and then with 2 equiv of sec-butyllithium.The trianions are highly nucleophilic at the 6 position.Alkylation with benzyl chloride, aldol condensation with benzophenone, and acylation with methyl benzoate gave terminal condensation products but methyl acetate failed to condense with the trianions, proton transfer from the acetyl methyl group occurring instead.Both trianions underwent β-ketoacylationwith methyl benzoylacetate but only the diketo ester trianion condensed with methyl acetoacetate.The resulting 1,3,5,7,9-pentacarbonyl compounds underwent cyclization reactions to give aromatic products.Complex aromatic products derived from 1,3,5,7,9,11-hexacarbonyl compounds were obtained from condensations of the diketo ester trianion with 4-methoxy-6-methyl-2-pyrone and of the diketo amide trianion with 4-methoxy-6-phenyl-2-pyrone.