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Dodecyl benzenesulfonic acid functionalized silica-coated magnetic nanoparticles (γ-Fe2O3@SiO2-DDBSA) were readily prepared and identified as an efficient catalyst for the synthesis of a library of spirooxindole-pyrimidine derivatives by three-component condensation reaction of barbituric acids, isatins and cyclohexane-1,3-diones. The aqueous reaction medium, easy recovery of the catalyst using an external magnet, and high yields make the protocol sustainable and economic.

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Carbonyl Compounds. -A novel and environmentally friendly procedure for the title reaction (85 examples), which uses an easily prepared and reusable catalyst, is developed. The compound (VI) reacts without racemization under these conditions. The catalyst is easily separated from the reaction mixture using an external magnet and reused for six cycles without significant loss of activity. -(DENG, J.; MO, L.-P.; ZHAO, F.-Y.; HOU, L.-L.; YANG, L.; ZHANG*, Z.-H.; Green Chem. 13 (2011) 9, 2576-2584, http://dx.