Bis-GO@SiO₂@[(CH₂)₃Im][Cl] nanocatalyst: a mild, reusable, and sustainable multicomponent platform for the synthesis...

The development of efficient and environmentally friendly catalytic systems for making sulfur-containing heterocycles remains an important goal in synthetic chemistry. Here we describe a new hybrid nanocatalyst, Bis-GO@SiO₂@[(CH₂)₃Im][Cl], that combines bis-functionalized graphene oxide, a silica coating, and an immobilized imidazolium-based ionic liquid. This material works as a highly active and recyclable platform for the multicomponent synthesis of 2-thioarylbenzoazoles. The method tolerates a wide range of substrates and gives consistently high isolated yields, between 90% and 97%, for a library of 20 different derivatives. The catalyst can be easily recovered and reused for six consecutive cycles without any notable drop-in activity. Using potassium carbonate as a base in DMF at 50 °C, the catalyst directly couples benzimidazoles, benzoxazoles or benzothiazoles with aryl halides and elemental sulfur (S₈) under very mild conditions. The whole process follows a three-component reaction strategy and gives a wide range of structurally diverse 2-thioarylbenzoazole derivatives in high to excellent yields. The immobilized ionic liquid layer, together with the high-surface-area graphene oxide-silica support, helps disperse the active sites, improves their accessibility, and enhances stability. Various characterization techniques confirmed that the nanocatalyst had been successfully prepared and that its structure remained intact. By combining simple operation, a low reaction temperature, and catalyst recyclability, this method offers a practical and greener alternative to existing ways of making these valuable heterocyclic scaffolds, which should be of interest for applications in medicinal chemistry and materials science.