A Nano-sized Nd–Ag@polyoxometalate Catalyst for Catalyzing the Multicomponent Hantzsch and Biginelli Reactions

For the first time the catalytic activity of AgNdSiW₁₁, was examined in two named reactions, namely Hantzsch and Biginelli reactions. A simple, eco-friendly and highly efficient one-pot synthesis of polyhydroquinoline derivatives via Hantzsch multicomponent reactions (MCRs) involving cyclocondensation of differently-substituted aldehydes, β-ketoesters or dimedone, active methylene compounds, and ammonium acetate as a source of nitrogen, in the presence of AgNdSiW₁₁ as a catalyst in EtOH/H₂O under reflux conditions in high yields was successfully achieved. Furthermore, the catalytic performance of AgNdSiW₁₁ was also successfully tested in the synthesis of 3,4-dihydropyrimidin-2-(1H)-ones via Biginelli MCR involving cyclocondensation of differently-substituted aldehydes, ethyl acetoacetate and urea as source of nitrogen in the presence of AgNdSiW₁₁ under reflux conditions in EtOH/H₂O. This prolific combination of Ln and POMs inaugurates a powerful class of catalysts for the different chemical transformations, which overcomes key limitations of previously established salts and Lewis acidic metals-based catalysts under low catalyst loading, the use of water scavengers, dry solvents and additives for facilitating the specialized experimental setups commonly employed to the organic reactions.