Wood ash biocatalyst as a novel green catalyst and its application for the synthesis of benzochromene derivatives

Abstract

Wood ash is a naturally alkaline derived substance containing organic and inorganic constituents. This study investigates the catalytic activity of wood ash as a heterogeneous catalyst for the synthesis of benzochromene derivatives. Several wood ash catalysts, comprising calcium- and potassium-rich carbonates, were prepared from different natural resources under various combustion temperatures. The prepared catalysts were characterized by Fourier transform infrared, scanning electron microscopy, energy dispersive X-ray analysis, transmission electron microscopy, and X-ray diffraction techniques. Catalytic efficiency of the resultant catalysts was tested in the synthesis of benzochromene derivatives. The experimental studies clarified that the catalyst prepared at 850 °C could efficiently expedite the formation of three-component synthesis of benzochromene derivatives in water at 80 °C with high yields. Indeed, alkali, alkaline metal, and metal oxides such as Al₂O₃, SiO₂, MgO, CaO, and Fe₂O₃, are widely utilized as both catalyst and catalyst support in the heterogeneous catalytic processes. The prepared wood ash catalysts (possessing metal oxides, e.g., CuO, Al₂O₃, SiO₂, and CaO) could effectively prompt the electrophilic activity of the carbonyl groups during the nucleophilic attack intermediate, enhancing the efficiency of the reactions.