Ultrasound-Assisted Cascade Condensation of Isatin, Malononitrile, and β-Keto Esters: An Efficient One-Pot Synthesis of Novel Spirooxindole Derivatives with Expected Anti-Esophageal Cancer Activity

A green and facile one-pot synthesis of novel oxospiro[indole-3,4′-pyran] derivatives via a three-component reaction of isatin, malononitrile, and various β-keto esters in the presence of triethylamine under ultrasonic irradiation is reported. This protocol offers several ecological benefits including simple methodology, good to excellent yields, clean reaction, higher atom economy, shorter reaction time, and environmental friendliness. Molecular docking of the synthesized spirooxindole derivatives was performed to evaluate their anti-esophageal cancer activity.