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.

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► Operational simplicity and high yields of products with minimized environmental impact factor.
► Environmental compatibility and non-toxicity, low cost, and ease of isolation.
► Simplified recovery and reusability of catalyst.
► Application of 2H-indazolo[2,1-b]phthalazine-triones in the synthesis of pharmaceuticals and agrochemicals.