An efficient synthesis of functionalized 2-pyridones by direct route or via amide/enolate ammonium salt intermediates

A number of compounds with a 2-pyridone structure 3, which have different s ubstituents and are analogous to cardiotonic drugs like milrinone, have bee n synthesized in high yields from the appropriate enamino ketones 2 using d ifferent cyanomethylene active compounds (methyl cyanoacetate, benzoylaceto nitrile and phenylsulfonylacetonitrile). In this synthetic route, the activ e role of the dimethylamine released in situ on the cyclization process has been underlined. In particular, its direct intervention, as a nucleophile or a base, was proven and intermediate amides 5 or enolate ammonium salts 6 were isolated and recognized by the analytical and spectral data.