Ionic-liquid and cuprous sulfite containing halloysite nanoclay: An efficient catalyst for Click reaction as well as N- and O-arylations

Abstract Using halloysite nanoclay (Hal) as a support and its multi-functionalization, a novel heterogeneous catalyst, Hal-IMI-SO 3 Cu, containing ionic liquid, copper species and sulfur trioxide was prepared and fully characterized by applying SEM/EDS, TEM, BET, ICP-AES, TGA, XRD and FTIR spectroscopy. Hal-IMI-SO 3 Cu exhibited excellent catalytic activity for the synthesis of triazoles through Click reaction of sodium azide, α-haloketones, alkyl halides and terminal alkynes as well as N -arylation and O -arylation of imidazole and phenol with aryl halides under mild and eco-friendly condition. The comparison of the catalytic activities of Hal–Cu, Hal-IMI-Cu (the catalyst without sulfur), Hal-SO 3 HCu (the catalyst without IL), Hal-IMI-SCu (the catalyst in which –SH was not oxidized to –SO 3 H) and Hal-IMI-SO 3 H (the catalyst without copper) with that of the catalyst for the Click reaction confirmed that copper played the dominant role in the catalysis. Moreover, the contribution of IL, and sulfur species to the catalysis was confirmed. It was also proved that the presence of –SO 3 H was more favorable than –SH. The recyclability tests confirmed that Hal-IMI-SO 3 Cu was highly recyclable, up to 10 reaction runs, with slight loss of the catalytic activity and copper leaching.