Synthesis of bis- and tris(indolyl)methanes catalyzed by an inorganic nano-sized catalyst followed by dehydrogenation to hyperconjugated products

Abstract

A set of bis- and tris(indolyl)methanes were prepared and dehydro­genated to their hyperconjugated products in a one-pot fashion. Nano-sized
–SO3H functionalized mesoporous KIT-6 coated on magnetite nanoparticles (Fe3O4@SiO2@KIT-6-OSO3H) was used as an efficient catalyst in the first step of the synthesis, and dehydrogenation was completed using (NH4)2S2O8 after removal of the catalyst. The catalyst was fully characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and X-ray powder diffraction (XRD), as well as by its nitrogen ads­orption–desorption isotherms. The bis- and tris(indolyl)methanes were studied by UV–Vis spectroscopy before and after dehydrogenation, and effect of the ambient parameters on their spectra was investigated. It was found that bis- and tris(indolyl)methanes have no considerable absorption in the visible range but their partial dehydrogenation due to exposure to air makes them colored. The catalyst, as a new combination of known materials, showed superiority in terms of yield, time, and mild reaction conditions in comparison with those reported previously.