Copper incorporated into 1H-1,2,3-triazole-5-methanol functionalized halloysite nano clay as an efficient and heterogeneous catalyst for promoting green A3 and KA2 coupling reaction: Optimization of reaction variables using response surface methodology

Abstract Design and synthesis of a novel heterogeneous catalyst based on functionalization of halloysite nanoclay with 1 H -1,2,3-triazole-5-methanol and subsequent incorporation of copper is disclosed. The obtained catalyst was fully characterized by employing ICP-AES, SEM/EDX, TGA, XRD, BET and FTIR and successfully used for promoting the A 3 and KA 2 coupling reactions of phenylacetylene, amines and aldehydes or ketone in aqueous media. The reaction variables including reaction temperature and amount of the catalyst were optimized using Response Surface Methodology (RSM). The catalyst exhibited excellent catalytic activity under optimum reaction condition. Notably, the investigation of the reusability of the catalyst confirmed that the catalyst could be recovered and reused up to four reaction runs with only slight loss of the catalytic activity. The hot filtration experiment also demonstrated low leaching of copper species, indicating the heterogeneous nature of the catalysis. Easy work-up procedures, performing the reaction in aqueous media, broad range of substrate scope and low reaction times are other merits of this protocol.