A simple, straightforward and efficient method has been developed for the synthesis
of (E)-3-(arylimino)indolin-2-one derivatives and (E)-2-((4-methoxyphenyl)imino)-
acenaphthylen-1(2H)-one. The synthesis of these biologically-significant scaffolds was
achieved from the reactions of various substituted anilines and isatins or acenaphthaquinone,
respectively, using commercially available, environmentally benign and naturally
occurring organic acids such as mandelic acid or itaconic acid as catalyst in aqueous medium
at room temperature. Mild reaction conditions, energy efficiency, good to excellent
yields, environmentally benign conditions, easy isolation of products, no need of column
chromatographic separation and the reusability of reaction media are some of the significant
features of the present protocol.