Heterogenization of amine-functionalized ionic liquids using graphene oxide as a support material: a highly efficient catalyst for the synthesis of 3-substituted indoles via Yonemitsu-type reaction

In the present study, heterogenization of amine-functionalized ionic liquids was developed via covalent immobilization of 2-chloroethylamine on imidazole modified graphene oxide (GO) sheets. The prepared material was characterized by various physicochemical techniques such as Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) spectroscopy. The prepared material was employed as an efficient heterogeneous catalyst for the synthesis of 3-substituted indoles via Yonemitsu-type reaction. The catalyst could be easily separated from the reaction mixture through centrifugation and could be reused for seven consecutive cycles without any appreciable loss in its catalytic activity.