Fe3O4@nano-cellulose/TiCl: a bio-based and magnetically recoverable nano-catalyst for the synthesis of pyrimido[2,1-b]benzothiazole derivatives

Abstract

Magnetic core–shell nanoparticles, Fe₃O₄@nano-cellulose, are prepared through in situ co-precipitation of Fe³⁺ and Fe²⁺ ions via NH₄OH in an aqueous solution of nano-cellulose. Treatment of Fe₃O₄@nano-cellulose with titanium tetrachloride leads to the formation of Fe₃O₄@nano-cellulose/TiCl as a novel recyclable catalyst. Subsequently, the structure, morphology, and magnetic properties of the prepared nano-catalyst were studied with some different techniques such as Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), X-ray fluorescence (XRF), vibrating sample magnetometry (VSM) and thermo-gravimetric analysis (TGA). The catalyst was found to be active for the synthesis of 4H-pyrimido[2,1-b]benzothiazoles via one-pot three-component reaction of aldehydes, ethyl acetoacetate and 2-aminobenzothiazole under solvent-free condition at 70 °C. This procedure offers the advantages of mild reaction conditions, easy work-up, excellent yields, short reaction time and simple magnetic separation of the catalyst and its recyclability up to seven cycles without any considerable loss of efficiency.