Ultrasound-Promoted preparation and application of novel bifunctional core/shell Fe 3 O 4 @SiO 2 @PTS-APG as a robust catalyst in the expeditious synthesis of Hantzsch esters

Abstract

Abstract In this work, D-(−)-α-phenylglycine (APG)-functionalized magnetic nanocatalyst (Fe3O4@SiO2@PTS-APG) was designed and successfully prepared in order to implement the protocols of green chemistry for the synthesis of polyhydroquinoline (PHQ) and 1,4-dihydropyridine (1,4-DHP) derivatives under ultrasonic radiation in EtOH. After preparing the nanocatalyst and confirming its structure by different spectroscopic methods or techniques including Fourier transform infrared (FT-IR) spectroscopy, energy-dispersive X-ray spectroscopy (EDS), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and thermal gravimetric analysis (TGA). Its performance under ultrasonic radiation and various conditions were examined. The yield of target derivatives was controlled under various conditions and it was found that it reaches more than 80% in just 10 min, which indicates the high performance of the nanocatalyst along with the synergistic effect of ultrasonic radiation. The structure of the products was identified by melting point as well as FT-IR and 1H NMR spectroscopic methods. The Fe3O4@SiO2@PTS-APG nanocatalyst is easily prepared from commercially available, lower toxicity and thermally stable precursors through a cost-effective, highly efficient and environmentally friendly procedure. The advantages of this method include simplicity of operation, reaction under mild conditions, use of environmental radiation sources, obtaining pure products with high efficiency in the shortest time without using a tedious path which is all in the shadow of green chemistry. Finally, a reasonable mechanism is proposed for the preparation of polyhydroquinoline (PHQ) and 1,4-dihydropyridine (1,4-DHP) derivatives in the presence of Fe3O4@SiO2@PTS-APG bifunctional magnetic nanocatalyst.