12-Tungstophosphoric Acid Immobilized on γ-Fe2O3@SiO2 Core–Shell Nanoparticles: An Effective Solid Acid Catalyst for the Synthesis of Indole Derivatives in Water
12-Tungstophosphoric Acid Immobilized on γ-Fe<sub>2</sub>O<sub>3</sub>@SiO<sub>2</sub> Core–Shell Nanoparticles: An Effective Solid Acid Catalyst for the Synthesis of Indole Derivatives in Water
12-Tungstophosphoric acid immobilized on γ-Fe2O3@SiO2 core–shell nanoparticles was used as novel solid acid catalyst for the synthesis of various bis(indolyl)methanes and β-functionalized indoles in water. The catalyst can be recovered simply using an external magnetic field and reused several times without appreciable loss of its catalytic activity.