CaFe2O4@SiO2-Cu as a novel and highly efficient nanocatalyst for direct conversion of epoxides to β-acetoxy esters

Direct conversion of structurally various epoxides to the related β-acetoxy esters was investigated using catalytic amounts of CaFe₂O₄@SiO₂-Cu. The reactions were accomplished in the presence of acetic anhydride under solvent-free conditions within 0.5-2 h to give desired products in high yields. Initially, the CaFe₂O₄ nanoparticles were manufactured through a chemical coprecipitation reaction of calcium nitrate and hydrated iron (III) nitrate in the presence of ammonium hydroxide solution, and then calcined at 800 ºC. Next, to protect the prepared CaFe₂O₄ from oxidation and aggregation, its surface was covered with a silica layer to give CaFe₂O₄@SiO₂. Eventually, by adding copper chloride solution followed by potassium borohydride solid powder, Cu nanoparticles were successfully immobilized on the silica surface and the new CaFe₂O₄@SiO₂-Cu nanocomposite was obtained. FT-IR, SEM, EDX, VSM, ICP-OES, TGA, TEM and XRD techniques were employed to characterize the newly synthesized nanostructure. In addition, durability of the catalyst was considered for several sequential reaction cycles without the notable loss of catalytic activity. The absence of hazardous organic solvents, high product yields, short reaction times and recoverability of the magnetic catalyst are among the remarkable advantages of the introduced procedure.