Construction of Fully Substituted 2-Pyridone Derivatives via Four-Component Branched Domino Reaction Utilizing Microwave Irradiation.

Microwave irradiation, four-component branched domino reaction of methyl acetoacetate/2,4-pentanedione, diethyl malonate, triethyl orthoformate and amines offering an extremely efficient strategy for the construction of fully substituted 2-pyridone derivatives under sustainable conditions is established. This self-sorting branched domino transformation is proposed to proceed separate through N-nucleophilic addition and imine-enamine tautomerization/condensation reaction generated from enamino ester and diethyl ethoxymethylenemalonate, and then would be subjected to an aza-ene reaction and intramolecular cyclization mechanism to afford the 2-pyridones with only water and ethanol as byproducts. The simple experimental procedure, high bond-forming efficiency, step and atom economy, inexpensive readily available starting materials, moderate to excellent yields, and good functional group compatibility are other noteworthy advantages of this method.