Magnetic biochar‐supported ZrO ₂ as an efficient catalyst for one‐pot synthesis of 1′,4′‐dihydro‐3 H,3′ H‐spiro[furo[3,4‐ b]quinoline‐9,2′‐quinoxaline]‐1,3′(4 H)‐diones

Abstract

A novel ZrO ₂ supported on a magnetic biochar material (CoFe ₂O ₄/BC‐ZrO ₂) was synthesized using a relatively simple route. The prepared CoFe ₂O ₄/BC‐ZrO ₂ was characterized by X‐ray diffraction (XRD), Fourier transform infrared (FT‐IR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy‐dispersed X‐ray (EDX) elemental analysis, N ₂ adsorption–desorption isotherm, thermogravimetric analysis (TGA), and magnetic properties. The CoFe ₂O ₄/BC‐ZrO ₂ showed high catalytic activity for the synthesis of spiro[furo[3,4‐ b]quinoline via a one‐pot three‐component reaction of benzene‐1,2‐diamine, indoline‐2,3‐dione, and tetronic acid. The catalyst can be recovered by an external magnetic field and recycled at least five times without significantly reducing its activity.