An Fe3O4@keratin nanocomposite doped with copper(ii): a reusable heterogeneous catalyst for the synthesis of novel 1,4-disubstituted 1,2,3-triazole-pyrimido-benzimidazoles in aqueous ethanolic solution under ultrasound cavitation†

A novel magnetic nanocatalyst, Fe₃O₄@keratin-Cu(II), was developed via simple aqueous-phase immobilization of Cu(II) onto a keratin-coated Fe₃O₄ surface, with keratin extracted from chicken feathers through ultrasonic-assisted alkaline-oxidative hydrolysis. This catalyst enabled a rapid and green sequential two-step, one-pot synthesis of 1,2,3-triazolo-pyrimido-benzimidazole derivatives 5a–x in good to excellent yields (64–90%). The protocol involves microwave-assisted propargylation of benzimidazo[1,2-a]pyrimidinone followed by a CuAAC “click” reaction with azides under ultrasonic cavitation. The Fe₃O₄@KNPs-Cu(II) nanocatalyst showed very high activity for the click reaction and demonstrated excellent recyclability over five cycles without loss of activity. The structures of the nanocomposite and products 5a–x were fully characterized using FT-IR, XRD, SEM-EDX, ICP-OES, AFM, TEM, HRTEM, TGA, DSC, ¹H NMR, ¹³C NMR, ¹⁹F NMR, and HRMS techniques. The use of ultrasound significantly enhanced the reaction rate, offering a clean and efficient synthetic route.