Fe3O4@MCM-41-SO3H@[HMIm][HSO4]: An effective magnetically separable nanocatalyst for the synthesis of novel spiro[benzoxanthene-indoline]diones

Abstract

Synthesis of novel spiro[benzo[a]xanthene-12,3′-indoline]-2′,11(8H)-diones and spiro[benzo[c]xanthene-7,3′-indoline]-2′,8(9H)-diones were evaluated by three type of MCM-41 mesoporous magnetite nanoparticles Fe3O4@MCM-41-(CH2)3–SO3H, Fe3O4@MCM-41-SO3H and Fe3O4@MCM-41-SO3H@[HMIm][HSO4] as heterogeneous solid acid catalysts and 1-methylimidazolium hydrogen sulfate ([HMIm][HSO4]) as homogeneous acid catalyst in terms of activity and recyclability. The activity of Fe3O4@MCM-41-SO3H@[HMIm][HSO4] was comparable to those of the other heterogeneous and homogeneous catalysts. The structures of the products were characterized by their physical constants, IR, 1H NMR and 13C NMR spectroscopy. The ability to reuse the magnetite nanoparticle, high yield, short reaction time, solvent free conditions and ease of purification of products are the important features of this process.