Silica-supported NiO nanocomposites prepared via a sol–gel technique and their excellent catalytic performance for one-pot multicomponent synthesis of benzodiazepine derivatives under microwave irradiation

Abstract

Heterogeneous and versatile NiO–SiO₂ NCs were synthesized by a sol–gel technique and used as a catalyst for the one-pot multicomponent synthesis of benzodiazepine derivatives (4a–u) from a mixture of o-phenylenediamine, aromatic aldehydes and dimedone under microwave irradiation. Tetraethyl orthosilicate (TEOS) was used as a source of SiO₂ for the creation of the NiO–SiO₂ NCs. This catalytic protocol has many advantages, such as simple work up, inexpensive precursors, short reaction time, high yield and high surface area. The structure and morphology of the prepared nanocatalyst was characterized by using elemental analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDAX) and Fourier transform infrared (FTIR) spectroscopy. ¹H NMR, ¹³C NMR and MS analyses were performed to confirm the synthesized compounds (4a–u). Moreover, the remarkable catalytic properties of the NiO–SiO₂ NCs permit easy separation of the catalyst from the reaction mixture without significant loss of catalytic activity.