Synthesis of spiro[benzochromeno[2,3-d]pyrimidin-indolines] using Fe3O4@MCM-41-SO3H@[HMIm][HSO4] as a magnetically separable nanocatalyst

Three types 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 were evaluated for the synthesis of spiro[benzochromeno[2,3-d]pyrimidin-indolines] in terms of activity and recyclability. Their catalytic activities were compared with those of the homogeneous acid catalyst 1-methylimidazolium hydrogen sulfate ([HMIm][HSO4]). The activity of Fe3O4@MCM-41-SO3H@[HMIm][HSO4] was comparable to those of the other heterogeneous and homogeneous catalysts.