Organic–inorganic hybrid polyoxometalates: Efficient, heterogeneous and reusable catalysts for solvent-free synthesis of azlactones

Abstract

Two organic–inorganic hybrid polyoxometalates, consist of 1-butyl-3-methylimidazolium salts of (W 10O 32) 4− and (PW 12O 40) 3− polyanions were prepared and characterized by thermal analysis, X-ray diffraction, FT-IR, diffuse reflectance UV–Vis spectroscopic methods and nitrogen absorption–desorption determination (BET). These heterogeneous catalysts were used for synthesis of azlactones by the reaction of aldehydes with hippuric acid and acetic anhydride under solvent-free conditions. These catalysts were reused several times without loss of their activities.