Green and efficient synthesis of aryl/alkylbis(indolyl)methanes using Expanded Perlite-PPA as a heterogeneous solid acid catalyst in aqueous media

Expanded Perlite-Polyphosphoric acid (EP-PPA) as a novel, efficient, recyclable and eco-benign heterogeneous catalyst has been applied for the green and rapid synthesis of aryl/alkylbis(indolyl)methanes, in water, in good to excellent yields. The catalyst was characterized by XRF, FT-IR, TGA/DTG, ICP-OES, SEM-EDX and pH analysis. Importantly, the newly synthesized heterogeneous solid acid catalyst can be recovered and reused six times without any significant loss in its catalytic potential. The remarkable features of the present methodology are high conversions, shorter reaction times, cleaner reaction profiles and simple work-up procedures.