Green synthesis of novel pyrazolo‐fused benzophenazines using H 3 PW 12 O 40 as efficient and recyclable catalyst under microwave irradiation

A high‐yield, atom‐efficient, and green protocol for the synthesis of novel pyrazolo‐fused benzophenazines utilizing a multicomponent condensation reaction between 2‐hydroxynaphthalene‐1,4‐dione, o ‐phenylenediamine, aromatic aldehydes, and 4‐methylbenzenesulfonohydrazide in the presence of phosphotungstic acid (H 3 PW 12 O 40 ) under microwave irradiation (MWI) in EtOH is reported. We provide a novel series of 1 H ‐benzo[ a ]pyrazolo[3,4‐ c ]phenazine derivatives interesting for biological screening tests. This protocol offers several advantages satisfying many principles of green chemistry, including atom economy, energy saving, clean reactions, inexpensive reagents, reusability of H 3 PW 12 O 40 , the absence of any tedious work‐up or purification, and avoidance of hazardous or toxic reagents/catalysts/solvents.