Sulfonic acid functionalized ionic liquid in combinatorial approach, a recyclable and water tolerant-acidic catalyst for one-pot Friedlander quinoline synthesis.

SO(3)H-functionalized ionic liquid was successfully applied as a water tolerant-acidic catalyst for the one-pot domino approach quinoline synthesis in aqueous medium. Various types of quinolines from 2-aminoaryl ketones and beta-ketoesters/ketones were prepared in 85-98% yields using the catalytic system of SO(3)H-functionalized ionic liquid/H(2)O. The ionic liquids was synthesized in a combinatorial fashion. The quinoline products could be conveniently separated from the reaction mixture by filtration, indicating that the whole process was performed in water and exemplifying a green chemistry. More importantly, the catalyst could be easily recycled for five times without loss of much activity. The catalytic system, reported here, possesses advantages of both homogeneous and heterogeneous catalysts.