Three-component synthesis of hexahydropyridopyrimidine-spirocyclohexanetriones induced by microwave

Pyridopyrimidine-spirocyclohexanetriones (5, 6) and pyrimido[4,5-b]quinolinones (8) were obtained in a three-component microwave-assisted reaction of 6-aminopyrimidin-4-ones (1) with dimedone (2) and formaldehyde solution or paraformaldehyde, respectively. A mechanism is proposed based on the presence of a basic catalyst (triethylamine in this case) and the fact that single condensation intermediates are isolated prior to the cyclization leading to the final products.