Green synthesis of novel pyrazolo‐fused benzophenazines using H3PW12O40 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 (H3PW12O40) under microwave irradiation (MWI) in EtOH is reported. We provide a novel series of 1H‐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 H3PW12O40, the absence of any tedious work‐up or purification, and avoidance of hazardous or toxic reagents/catalysts/solvents. A high‐yielding, 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 (H3PW12O40) under microwave irradiation (MWI) in EtOH is reported. The novel series of 1H‐benzo[a]pyrazolo[3,4‐c]phenazine derivatives may be useful for biological screening tests.