A novel and efficient magnetic nanocatalyst functionalized with 1,3,5-tris(2-hydroxyethyl)isocyanurate and boric acid for the synthesis of symmetric and asymmetric Hantzsch esters

A new magnetic core/shell nanocatalyst functionalized with 1,3,5-tris(2-hydroxyethyl)isocyanurate and boric acid (Fe₃O₄/SiO₂/CPTS/THEIC/(CH₂)₃B(OH)₂) was designed and properly characterized by the Fourier transform infrared (FTIR) spectroscopy, nitrogen adsorption–desorption technique (BET), thermal gravimetric analysis (TGA) and X-ray diffraction (XRD), vibrating sample magnetometer (VSM), field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray (EDX) spectroscopy. The catalytic activity of Fe₃O₄/SiO₂/CPTS/THEIC/(CH₂)₃B(OH)₂, as an efficient magnetically recoverable catalyst, was investigated for the synthesis of polyhydroquinolines (PHQs) as well as polyhydroacridines (PHAs) via one-pot multicomponent reactions of ethyl acetoacetate and / or dimedone, different aldehydes and ammonium acetate in EtOH under reflux conditions. High to quantitative yields of the desired PHQs or PHAs products, wide scope of the substrates, eliminating of any toxic heavy metals or corrosive reagents for modification of the catalyst, simple work-up procedure, short reaction times and low loading of the catalyst are remarkable advantages of this green protocol. An additional advantage of this magnetic nanoparticles catalyst is its ability to be separated and recycled easily from the reaction mixture with minimal efforts in six subsequent runs without significant loss of its catalytic activity.