Magnetic Nanoparticles Based on DABCO as Catalysts in the Knoevenagel Reaction and Synthesis of Isatin-β-thiosemicarbazones

This work describes the route to prepare a novel core-shell catalyst based on 1,4-diazabicyclo[2,2,2]octane (DABCO) supported magnetic nanoparticles (MNPs). The morphology and composition of the obtained catalysts were characterized by Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), quantum design vibrating sample magnetometer (VSM) and scanning electron microscopy (SEM). These nanomaterials presented high performance as a basic catalyst for Knoevenagel condensation between malononitrile and aldehydes, leading to products with excellent yields (84-99%) and short reaction times (5-60 min). Furthermore, it was also efficient in the condensation of isatins with 4-phenylthiosemicarbazide, resulting in isatin-β-thiosemicarbazones with high yields (81-94%) and short times (60-180 min). It is worth mentioning that the catalyst was recovered and reused in these two kinds of reactions after six cycles without significant yield loss.