Michael condensation of 4-hydroxy-6-methylpyran-2-one with dimethyl acetylenedicarboxylate

Abstract

Methyl 7-methyl-2,5-dioxo-2H,5H-pyrano[4,3-b]pyran-4-carboxylate (I) has been synthesised by a Michael condensation of triacetic acid lactone (4-hydroxy-6-methylpyran-2-one) with dimethyl acetylenedicarboxylate. By-products of this reaction were dimethyl (6-methyl-2,4-dioxopyran-3-yl)maleate (II), dimethyl αβ-bis-(4-hydroxy-6-methyl-2-oxopyran-3-yl)succinate (III), and dehydroacetic acid (3-acetyl-6-methylpyran-2,4-dione). The differences between the products of this reaction and those previously obtained from a parallel condensation of triacetic acid lactone with ethyl propiolate are discussed in relation to the mechanism of Michael addition and the structures of the two acetylenic esters.