General procedure for the synthesis of pyrano[2,3-c]pyrazoles using crown ether as a catalyst. To a mixture of aromatic aldehyde 1a-p (2 mmol), 2 (2 mmol), 3 (2 mmol), 4a/4b (2 mmol) in water (10 mL) taken in a 50 mL RB flask, crown ether 10 mol% was added. The reaction mixture was subjected to sonication for 10 min at room temperature. The completion of reaction was confirmed using TLC. The solid product was filtered and recrystallized from aqueous ethanol to get the pure products.
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