Highly Active and Stable Bis Imidazolium-Based Copper N-heterocyclic Carbene Modified Graphene Oxide for O-arylation and N-arylation Reactions in Water

In this work, graphene oxide was synthesized and modified with 1,1'-((ethane-1,2-diylbis(oxy))bis(ethane-2,1-diyl))bis(3-(3-(triethoxysilyl)propyl)-1H-Imidazol-3-ium) chloride ionic liquid which acts as 2e-donor N-heterocyclic carbene ligand for decoration and stabilization of copper species. CuCl salt was anchored on ionic liquid modified surface of graphene to form copper/N-heterocyclic supported graphene oxide. The structure of ligand and final catalyst was characterized with various techniques such as NMR, FIIR, TGA, CHN, TEM, SEM, and ICP-OES. Successful immobilization of Bis-Im-IL on the GO via the condensation between C-OH groups of GO and alkoxyl groups of oxysilanes of ionic liquid was confirmed with FTIR. Thermal stability was enhanced when ionic liquid was attached to the surface of graphene. The wavy-shaped sheets with folded edges were observed in TEM and SEM images for both pure graphene oxide and modified graphene oxide. The Cu-NHC/GO catalyst was efficiently active in O-arylation reaction of phenols with aryl halides and O-arylation of azoles (imidazole, triazole and pyrazole) with aryl halides in water as reaction medium. High yields of products were obtained with this catalytic system. Also, this catalyst was active for 8 and 7 successful runs for O-arylation and N-arylation reactions, respectively. [GRAPHICS] .