Synthesis of some substituted pyrido[1,2-a]pyrimidin-4-ones and 1,8-naphthyridines

The substituted 4H-pyrido[1, 2-a]pyrimidin-4-ones (I) were obtained by the condensation of substituted 2-aminopyridines with δ-ketocarboxylic esters in PPA. Some of the derivatives I were transformed into the corresponding 1, 8-naphthyridines II and III.