An AlFe2O4@SiO2–SO3H innovative nanocatalyst: a sustainable approach for the A3 coupling reaction in a DES for 2-thioarylbenzoazoles†

The A3 coupling reaction, which facilitates the synthesis of 2-thioarylbenzoazoles, represents a significant transformation in organic chemistry with implications in drug discovery and materials science. In this study, we introduce a novel nanocatalyst, AlFe₂O₄@SiO₂–SO₃H, designed to enhance the efficiency and sustainability of this reaction. The catalyst is synthesized by functionalizing aluminum ferrite (AlFe₂O₄) with chlorosulfonic acid (Cl–SO₃H), promoting its role as an effective acid catalyst. Utilizing deep eutectic solvents (DESs) as a green reaction medium further contributes to the sustainability of the process by providing a biodegradable and non-toxic environment. Optimization studies were conducted to determine the optimal reaction conditions, including catalyst loading, temperature, and solvent composition. Characterization of the nanocatalyst was performed using techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR) to confirm successful synthesis and functionalization. The AlFe₂O₄@SiO₂–SO₃H nanocatalyst exhibited excellent catalytic activity, resulting in high yields of 2-thioarylbenzoazoles under mild conditions while allowing for easy recovery and reuse without significant loss of activity. This work demonstrates the potential of AlFe₂O₄@SiO₂–SO₃H as a sustainable catalytic system for A3 coupling reactions, contributing to the development of environmentally friendly methodologies in organic synthesis.