Covalently anchored 2-amino ethyl-3-propyl imidazolium bromideon SBA-15 as a green, efficient and reusable Brønsted basic ionic liquid nanocatalyst for one-pot solvent-free synthesis of benzopyranopyrimidines under ultrasonic irradiation

Abstract

In the present study, highly ordered mesoporous SBA-15 having Brønsted basic ionic liquid pore channels was synthesized via a surfactant-templated sol–gel methodology and a post modification process. For this, well ordered mesoporous chloro-functionalized SBA-15, SBA-Cl, was first synthesized by the direct incorporation of chloropropyl groups through the co-condensation of TEOS and CPTMS precursors in the presence of Pluronic P123 triblock copolymer as a supramolecular template to direct the organization of polymerizing silica. Subsequently, highly ordered 2-amino ethyl-3-propyl imidazolium bromide functionalized mesoporous SBA-15, SBA-Im-NH₂, with a high surface area was synthesized by a nucleophilic substitution reaction of SBA-Cl with imidazole and then quaternization with 2-bromo ethylamine hydrobromide. The target organic–inorganic nanocomposite was characterized by FT-IR spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), elemental analysis (CHN) and Brunauer–Emmett–Teller (BET) analysis. The SBA-Im-NH₂ nanocomposite was successfully used as an efficient Brønsted basic ionic liquid nanocomposite for the preparation of benzopyranopyrimidine derivatives by the one-pot pseudo four-components reaction of salicylaldehydes, malononitrile and secondary amines under ultrasonic and solvent-free conditions at room temperature. This method has the advantages of high yields, cleaner reaction, simple methodology, short reaction times, easy work-up, and greener conditions. In addition to the facility of this methodology, the catalyst also enhances product purity and promises economic as well as environmental benefits.