Imidazole mediated synthesis of spirooxindoles in water using isatin as a privileged scaffold

This work discusses the synthesis of complex small molecules spirooxindoles using imidazole as an efficient organocatalyst. The three components coupling reactions of isatin, malononitrile, and enolizable 4-hydroxycoumarin were performed in water as a green solvent. The reaction was done with imidazole, an amphoteric organocatalyst, to construct the spiro-molecules with high yields. The significant features of this protocol are neutral reaction condition, availability, low cost, metal free, strong acid/base free, and reusable reaction medium with no column chromatography separation. This methodology is useful for the easy access of structurally complex, highly functionalized spirooxindole molecules with the important medicinal chemistry applications.