Starch sulfate as an efficient and biodegradable polymer catalyst for one‐pot, four‐component reaction of 2 H ‐indazolo[2,1‐ b ]phthalazine‐triones

A practical and green method for the synthesis of 2 H ‐indazolo[2,1‐b]phthalazine‐1,6,11(13 H )‐trione derivatives using starch sulfate as a solid acid catalyst for the four‐component condensation reaction from hydrazinium hydroxide, phthalic anhydride, dimedone, and aromatic aldehydes under thermal solvent‐free conditions is described for the first time. Starch sulfate, a recyclable and easily handled catalyst has been demonstrated as a new catalyst for the synthesis of these classes of compounds.