Novel synthesis of pyridazino[4,5-b][1,4]oxazin-3,8-diones

Abstract A novel and effective synthesis of pyridazino[4,5- b ][1,4]oxazin-3,8-diones via Smiles rearrangement is presented. Treatment of N -substituted 2-chloro(or hydroxy)acetamide, 2-tetrahydropyranyl-4-chloro-5-hydroxy(or chloro)pyridazin-3-one and cesium carbonate in refluxing acetonitrile was afforded the corresponding pyridazino[4,5- b ][1,4]oxazin-3,8-diones in excellent yield.