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. (c) 2005 Elsevier Ltd. All rights reserved.