Microwave‐Assisted Synthesis of Pyridophenoxazinones, a Class of Antiproliferative Compounds

Microwave (MW) irradiation allows to prepare a mini‐library of pyridophenoxazinone derivatives, that are crucial intermediates in the synthesis of new antiproliferative compounds, active for human lymphoma/leukemia. The optimized procedure, consisting of a continuous input power of 50 W (80 °C) and a reaction time of 30 min, leads in very satisfactory yields to both regioisomers 5 H ‐pyrido[2,3‐ a ]phenoxazin‐5‐ones and isomeric 5 H ‐pyrido[3,2‐ a ]phenoxazin‐5‐ones, starting from readily available quinoline‐5,8‐dione and substituted 2‐aminophenols (APhOHs). Broad functional group tolerance was observed. The availability of derivatives carrying a carboxyl group at the C‐9 and C‐10 positions enables the synthesis of a new family of 5 H ‐pyridophenoxazin‐5‐one conjugates that were shown to exhibit good anti‐cancer activity.