A new multicomponent synthesis of pyrimido[4,5-b]quinolinetetraones

The synthesis of pirimido [4,5-b]quinolinestetraones is a topic of interest due to their biological properties.1,2 A new synthetic route was developed in a tricomponent form using a mixture of 2-amino-1,4-naphthoqui none (1), aromatic aldehydes (3a-f) and barbituric acid (2), producing 4a-e. Several conditions were tested, and the best result was obtained using reflux in acetonitrile and aminosulfonic acid as catalysis. This new methodology creates another option for the synthesis of this product. Replacing the reaction solvent by ethanol and removing the catalyst to adapt the process to the principles of green chemistry, a new reaction pattern was observed. The pyrimido [4,5-b]quinolinone-tetraones 5a-f were obtained with the formation of an exocyclic double bond, different from the pyrimido [4,5-b]quinolines-tetraones, where this double bond is endocyclic. Therefore, change the reaction condition, we developed a new method for the preparation of pyrimido[4,5-b]quinolinetetraones, and a catalyst-free method to a new series of pyrimido[4,5-b]quinolinonetetraones.