Abstract A convenient method leading to fused pyrido [1, 2-a][1, 3, 5] triazine-2-ones is described. It consists in a one-pot, two-step reaction of N-(2′-pyridinyl) benzoylacetamide with nitrosobenzenes. On the other hand, N-(2′-pyridinyl) acetoacetamide provides a C-2 condensation/addition product with nitrosobenzene. N-(2′-Pyridinyl) benzoylthioacetamide and N-(2′-pyridinyl) acetothioacetamide with nitrosobenzene undergo oxidative ...