Green synthesis of quinolines via A3-coupling by using graphene oxide-supported Bronsted acidic ionic liquid

Graphene oxide-supported Bronsted acidic ionic liquid ([GrBenzImi]SO3H) has been prepared by covalent grafting of benzimidazole unit in the matrix of graphene oxide followed by reaction with 1,4-butane sultone and hydrochloric acid. [GrBenzImi]SO3H has been characterized by various techniques including Fourier transform infrared spectroscopy (FTIR), FT-Raman (FT-Raman spectroscopy), CP-MAS C-13 NMR spectroscopy, thermogravimetric analysis, energy-dispersive X-ray analysis, Brunauer-Emmett-Teller surface area, X-ray diffraction, and transmission electron microscopy. [GrBenzImi]SO3H was successfully employed as heterogeneous catalyst in A(3)-coupling reaction of aryl aldehydes, anilines and phenylacetylene for the synthesis of 2,4-disubstituted quinolines using water/ethanol system (1:1) as green medium. [GrBenzImi]SO3H could be recycled six times without significant loss in the yield of product. Graphic abstract