One-pot, organocatalytic synthesis of spirooxindoles using citric acid in aqueous media

A facile and efficient multicomponent synthesis of functionalized spirooxindoles has been described through the reaction of isatin, malononitrile or ethyl cyanoacetate, and CH- acids (1,3-dicarbonyl compounds) in the presence of catalytic amount of citric acid in excellent yields with short reaction times in aqueous ethanol. Also, citric acid catalyzed synthesis of 3,3-diindolyl oxindoles by the condensation of isatin with substituted indoles.