Introduction of a novel nanosized N-sulfonated Brönsted acidic catalyst for the promotion of the synthesis of polyhydroquinoline derivatives via Hantzsch condensation under solvent-free conditions

In this research 4,4′-(butane-1,4-diyl)bis(1-sulfo-1,4-diazabicyclo[2.2.2]octane-1,4-diium)tetrachloride (NS-C 4 (DABCO-SO 3 H) 2 )·4Cl) as a new nano sized N -sulfonic acid was prepared and characterized using different types of methods including FT-IR, 1 H NMR, 13 C NMR, mass, XRD, TGA, SEM and AFM analysis. After the characterization of this reagent, it was efficiently used for the promotion of the one-pot synthesis of hexahydroquinolines via one-pot four-component condensation of aryl aldehydes, 1,3-cyclohexadione derivatives, β-ketoesters and ammonium acetate under solvent-free conditions. The procedure gave the products in excellent yields in short reaction times and good to high yields. Also this catalyst can be reused several times without loss of its catalytic activity.