Solvent-free, one-pot, four-component synthesis of 2H-indazolo[2,1-b]phthalazine-triones using sulfuric acid-modified PEG-6000 as a green recyclable and biodegradable polymeric catalyst

A green practical method for the efficient synthesis of 2H-indazolo[2,1-b]phthalazine-1,6,11(13H)-triones using sulfuric acid-modified polyethylene glycol-6000 (PEG-OSO3H) as an eco-friendly polymeric catalyst from the four-component condensation reaction of phthalic anhydride, hydrazinium hydroxide, 1,3-cyclohexanedione or 5,5-dimethyl 1,3-cyclohexanedione (dimedone) and aromatic aldehydes under solvent-free conditions at 80 °C is described. This approach allowed the environmental impact factor (E-factor) to be minimized.