Periodic mesoporous organosilica functionalized with <i>p</i>-aminobenzenesulfonic acid: an efficient solid acid catalyst for one-pot synthesis of 5-substituted 1<i>H</i>-tetrazoles under eco-friendly conditions

In this study, a new periodic mesoporous organosilica (PMO) functionalized with <i>p</i>-aminobenzenesulfonic acid (PABSA) was prepared <i>via</i> a novel co-condensation and sequential integration strategy. The obtained periodic mesoporous organosilica (PABSA-Pr-PMO) nanomaterial was characterized using various techniques, including Fourier-transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM), thermogravimetric/differential thermogravimetry analysis (TGA/DTA), the Brunauer-Emmett-Teller (BET) analysis, energy-dispersive X-ray spectroscopy (EDS), EDS elemental mapping, and X-ray diffraction (XRD). The thermally stable PABSA-Pr-PMO nanomaterial demonstrates high surface area, uniform particle size and well-defined active site as a solid acid. This material was successfully employed as an efficient catalyst for the synthesis of pharmaceutically relevant tetrazole derivatives <i>via</i> a cascade condensation and concerted 1,3-cycloaddition reaction. The desired 5-substituted 1<i>H</i>-tetrazole derivatives were efficiently synthesized through multicomponent reactions between aromatic aldehydes, malononitrile and sodium azide in the presence of PABSA-Pr-PMO in EtOH under reflux conditions. The protocol exhibited excellent yields and high purity. Low catalyst loading, short reaction times, and the use of environmentally friendly solvents such as EtOH and water, which replace the hazardous dimethylformamide (DMF) solvent, are significant advantages of this novel protocol. Additionally, the straightforward separation and recyclability of the catalyst, which maintains its activity for at least five consecutive runs without significant loss, contribute to its robustness and sustainability. This protocol can be distinguished by its efficiency, environmental friendliness, and sustained catalytic activity, highlighting it as an ideal method for the synthesis of 5-substituted 1<i>H</i>-tetrazole derivatives.