Hollow Fe3O4@DA-SO3H: an efficient and reusable heterogeneous nano-magnetic acid catalyst for synthesis of dihydropyridine and dioxodecahydroacridine derivatives

Abstract

In this work, for the first time, a highly stable and efficient super-paramagnetic catalyst, H-Fe3O4@DA-SO3H, involving hollow morphology of Fe3O4 as core and dopamine as shell was prepared through hydrothermal template-free method. It has been used as a new and recoverable catalyst for various one-pot multi-component organic reactions such as synthesis of 1,4-dihydropyridine (1,4-DHP) and 1,8-dioxodecahyroacridine derivatives. The new magnetic catalyst was characterized with different analyses including X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), vibrating sample magnetometer (VSM) and thermogravimetric analysis (TGA). Moreover, the ρ shell of the prepared hollow-Fe3O4 microparticles was calculated, being found just slightly lighter than that of solid sphere-like Fe3O4. The catalyst was conventionally recovered, using an external magnet and reused at least in six successive runs, without appreciable loss of its activity.