Copper Oxide Supported on Silica (CuO/SiO2): A Highly Efficient Heterogeneous Catalyst for the Synthesis of 1,2-Dihydroquinazolines at Room Temperature

A copper oxide supported on silica (CuO/SiO2) catalyst has been prepared which catalyzes a three-component reaction between 2-aminobenzopenone, benzaldehyde, and ammonium hydroxide leading to a convenient synthesis of 1,2-dihydroquinazoline. The main advantages of the process over the previous reports are room temperature reaction, selective formation of 1,2-dihydroquinazoline as a sole product, and recyclability of the catalyst. Seventeen derivatives with various substituents are prepared. The catalyst (fresh and recovered) has been fully characterized using HR-TEM, BET Surface area, XPS, FTIR, and XRD. The enhanced activity and selectivity of the catalyst (towards 1,2-dihydroquinazoline) is attributed to the formation of Cu-O-Si type surface structure which is also explained by the help of different analytical techniques. Further, the reaction was performed without a catalyst, with CuO and SiO2 separately. Based on catalyst characterization and experimental results a possible mechanism has been proposed and discussed thoroughly. Recovery and reusability of the catalyst have also been studied.