Micelle‐Mediated In‐water Synthesis of Spirooxindoles at Ambient Temperature Using Sapindus mukorossi Fruit Pericarp Powder as the Source of Saponin Surfactants

Micellar catalysis, which involves the use of surface‐active molecules, has evolved as a powerful tool in developing green synthetic protocols as it allows water to be used as a solvent. However, the environmental pollution caused by synthetic surfactants has been a major issue of concern. To address this problem, we have demonstrated the use of natural surfactants. Saponins derived from the fruit pericarp of Indian soapberry ( Sapindus mukorossi ) have been successfully used for the synthesis of spirooxindoles, namely, spiro[indoline‐3,5'‐pyrano[2,3‐ d ]pyrimidin]‐2‐ones and spiro[indoline‐3,4'‐pyrano[3,2‐ c ]chromen]‐2‐ones by reacting isatins and malononitrile with barbituric acids and 4‐hydroxycoumarins, respectively, in water under mild conditions.