A new synthetic approach to functionalize pyrimido[4,5-<Emphasis Type="Italic">b</Emphasis>]quinoline-2,4(1<Emphasis Type="Italic">H</Emphasis>,3<Emphasis Type="Italic">H</Emphasis>)-diones via a three-component one-pot reaction

Functionalized pyrimido4,5-b]quinoline-2,4 (1H,3H)-diones were synthesized by a three-component one-pot reaction involving barbituric acid, aldehydes, and anilines. The use of commercially available anilines allowed the facile syntheses of pyrimido4,5-b]quinolinediones substituted in all the positions on the benzene ring with electron donor or electron withdrawing groups. This straightforward method circumvents the preparation of unstable substituted 2-aminobenzaldehydes that limits the scope of previously described syntheses. Furthermore, access to the 5-substituted derivatives is now also possible starting from aliphatic or aromatic aldehydes. Our strategy and methodology offer significant and practical improvements over other methodologies.