Polymer grafted layered double hydroxides (LDHs-g-POEGMA): a highly efficient reusable solid catalyst for the synthesis of chromene incorporated dihydroquinoline derivatives under solvent-free conditions

摘要

A novel poly(oligoethylene glycol methacrylate)-g-supported layered double hydroxides (LDHs-g-POEGMA) with high surface area with easy accessibility of active sites was successfully prepared for the first time via an efficient sequential synthetic procedure and characterized by FT-IR spectroscopy, XPS spectra, thermogravimetric analysis (TGA), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and NMR spectroscopy. The obtained green catalyst was used as an effective, inexpensive, environmentally friendly, and highly active reusable heterogeneous solid catalyst for synthesis of chromene incorporated dihydroquinoline derivatives via a one-pot three-component condensation of 4-hydroxy-2H-chromen-2-one, aromatic amines, and various aldehydes under solvent-free conditions. The notable features of this "green" reaction are good to excellent yields, shorter reaction times, avoidance of toxic solvents, and substrate diversity. Herein we also observed that the LDHs-g-POEGMA is highly stable under reaction conditions and can be separated easily from the reaction mixture, and, therefore, can be reused for several consecutive runs without any apparent loss in its catalytic activity.