A clean and expedient synthesis of spirooxindoles catalyzed by silica–sulfuric acid nanoparticles as an efficient and reusable reagent Bahareh Sadeghi • Maryam Ghasemi Pirbaluti • Parinaz Farokhi Nezhad • Reza Abbasi Nezhad Received: 6 May 2013 / Accepted: 9 December 2013 Ó Springer Science+Business Media Dordrecht 2013 Abstract An atom-efficient, one-pot, three-component synthetic method, using silica–sulfuric acid nanoparticles as catalyst, has been developed for preparation of biologically important spirooxindoles. The reaction involves the use of isatin or 5-fluoroisatin, malononitrile, and enolizable systems. A wide range of enolizable systems can be used in this reaction, furnishing excellent yields in a short time. The catalyst is recyclable with reproducible results without any loss of its activity. The morphology of the silica–sulfuric acid nanoparticles was observed by scanning electron microscopy. Some of the compounds were new and their structures were deduced by elemental and spectral analysis (IR, 1 H NMR, and 13 C NMR). More- over, column chromatography and recrystallization of the products is not required because the crude products are already highly pure. Keywords Spirooxindoles Á 5-Fluoroisatin Á Malononitrile Á Enolizable system Á Silica–sulfuric acid nanoparticles Introduction Recently, multi-component, one-pot syntheses have become extremely attractive reactions because of their vast applications. These reactions are widely used in the pharmaceutical chemistry for producing different structures and combinatorial libraries for drug discovery [1–3]. Spirooxindole derivatives include numerous natural products and they are dominant molecules in medicinal chemistry, for example pteropodine, horsfiline, isopteropodine, and spirotryprostatin A and B (Fig. 1)[4]. Biological studies show that the presence of two different heterocyclic moieties in a single molecule often dramatically enhances biological activity [5–7]. B. Sadeghi (&) Á M. Ghasemi Pirbaluti Á P. Farokhi Nezhad Á R. Abbasi Nezhad Department of Chemistry, Yazd Branch, Islamic Azad University, PO Box 89195-155, Yazd, Iran e-mail: bsadeghia@gmail.com 123 Res Chem Intermed DOI 10.1007/s11164-013-1509-1