Heteropolyacid@creatin-halloysite clay: an environmentally friendly, reusable and heterogeneous catalyst for the synthesis of benzopyranopyrimidines

A novel hybrid catalyst has been designed and synthesized based on the incorporation of heteropolyacid into creatin-functionalized halloysite clay. The catalyst was characterized by using SEM/EDS, FTIR, XRD, BET, ICP-AES, TGA and DTGA, and successfully applied for promoting the synthesis of two series of benzopyranopyrimidines under ultrasonic irradiation in aqueous media. The results established the efficiency of this protocol in terms of product yield, reaction time and the eco-friendly nature of the process. Moreover, immobilization of heteropolyacid on creatin-functionalized halloysite circumvents heteropolyacid leaching and rendered the catalyst highly reusable.