Reaction of (E)-β-enamino amides with dimethyl acetylenedicarboxylate (DMAD): formation of benzene derivatives, enamino esters, and 2-pyridones

Abstract

An investigation of the additions of (E)-enamino amides (1a–d) with DMAD has shown that they are influenced by the stereochemistry of the intermediates and the amine component of the enamine system. In dryacetonitrile (E)-benzyl(methyl)amino-(1b), (E)-pyrrolidin-1-ylamino-(1c), and (E)-piperidin-1-ylamino-(1d) acrylamides, following a known mechanism, yielded tetramethyl benzene-1,2,3,4-tetracarboxylate (5), the (E)-aminobutenedioates (6b–d), and the 3,4-bismethoxycarbonylpyridin-2-(1H)-one (8). Dimethylamino-(1a) and morpholin-1-ylamino-(1e)-acrylamides, owing to the different nucleophilicity of the β-carbon, formed a zwitterion (11) which eliminated propiolamide to give only the (E)-aminobutenedioates (6a, e).