Rapid and efficient one-pot synthesis of spiro[indoline-3,4′-pyrano[2, 3-c]pyrazole] derivatives catalyzed by l-proline under ultrasound irradiation

• Ultrasound-promoted one-pot synthesis of spiro-pyrano[2,3-c]pyrazoles was developed.
• Good to excellent yields were achieved within shorter reaction time.
• Fused heterocylces were obtained in aqueous media catalyzed by l-proline.

A rapid and efficient ultrasound-promoted one-pot synthesis of spiro[indoline-3,4′-pyrano[2,3-c]pyrazole] derivatives is described here. The reaction of substituted phenylhydrazine and dialkyl acetylenedicarboxylate with substituted isatin and malononitrile is catalyzed by l-proline to give good-to-excellent yields in water/ethanol (v/v, 1:1) at room temperature.

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