CuI@amine-functionalized halloysite as an efficient heterogeneous catalyst for promoting A3 coupling reaction under ultrasonic irradiation: a combination of experimental and DFT simulation

Two novel hybrid catalysts based on incorporation of CuI in amine-functionalized halloysite using two different amine functionalization agents, i.e. 3-aminopropyl-triethoxysilane, APTES, and N-[3-(trimethoxysilyl)propyl] ethylenediamine, AEAPTMS, have been synthesized and characterized by using SEM/EDX, XRD, FTIR, ICP, BET, and TGA. Furthermore, the ability of the ligands toward CuI adsorption in the gas and solution phases were compared quantitatively using DFT simulation. The results showed that AEAPTMS-functionalized halloysite has more affinity toward CuI adsorption, which decreases catalyst leaching. This catalyst was successfully used for promoting A3 coupling reaction of aldehydes, phenyl acetylene and amines under ultrasonic irradiation to furnish the corresponding propargylamines in short reaction time and high yields. The synthesized catalyst exhibited high reusability and could be recovered and reused, preserving its catalytic activity.