Direct Access to Novel Chromeno-Pyrimidine-N-Oxides via Tandem Base Catalyzed Double Nucleophilic Addition/Dehydration Reaction

The document described a new method for synthesizing chromeno-pyrimidine-N-oxides, which are important in medicinal chemistry and used in drugs like Minoxidil for treating androgenic alopecia. The synthesis was achieved through a tandem base-catalyzed double nucleophilic addition and dehydration reaction, using sodium bicarbonate as the base in ethanol at 60°C. The process produced regioselective pyrimidine mono-N-oxide products in 65-88% yields without the need for column purification. The method worked well with aromatic substrates but not with aliphatic ones, and the structure of a product was confirmed by X-ray analysis. This study offers a new approach for the synthesis of pyrimidine-N-oxides, potentially aiding further research and drug development.