Sulfonated nanoClay minerals as a recyclable eco-friendly catalyst for the synthesis of quinoxaline derivatives in green media

Sulfonated nanoClay was prepared by reacting a mixture of nanoClay mineral particles with 3-aminopropyltriethoxysilane (APTES) in dry toluene under N2 and subsequent treatment with propane sultone. The synthesized sulfonated nanoClay was characterized with FTIR spectroscopy, elemental analysis, thermogravimeteric analysis (TGA), SEM and atomic force microscopy (AFM). The result showed particle sizes between 30 and 38 nm. TGA indicated a 70% loading of SO3− group which was confirmed by elemental analysis. Synthesized sulfonated nanoClay was tested in the synthesis of quinoxaline derivatives via the condensation of 1,2-diamines with 1,2-diketones in ethyl alcohol as a green medium at room temperature. Using this method, the title compounds were prepared in high yields and short reaction times. The catalyst was recovered and reused several times without significant loss of catalytic activity. AFM and SEM of recycled catalyst showed a uniform distribution with a particle size of 40 nm and little aggregation.