Synthesis of Chromenes using functionalized SBA-15

Functionalized SBA - 15 (Immobilization of Pd on the modified SBA - 15) has been utilized as an efficient catalyst for the preparation of chromenes by multi-component reactions of aromatic aldehydes, malononitrile and 4-hydroxycoumarin under reflux in ethanol. The catalyst has been characterized by X - ray diffraction spectroscopy ( XRD ), Field emission scanning electron microscopy ( FE - SEM ), Transmission electron microscopy (TEM), Energy-dispersive X - ray spectroscopy ( EDX ), X - Ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT - IR), N2 adsorption analysis, Temperature Programmed Desorption (TPD), and Differential thermal analysis (TGA - DTA). The structures of the products were deduced from their 1 H NMR, 13 C NMR, FT - IR, and elemental analyses. The advantages of this method include the reusability of the catalyst, low catalyst loading, excellent yields in short reaction times and easy separation of products, with no recrystallization required.