CsxH3−xPW12O40 heteropoly salts catalyzed quinoline synthesis via Friedländer reaction

Various type of cesium partially substituted phosphotungstate, CsxH3−xPW12O40 (x = 1.0, 2.0 and 2.5), were synthesized and their catalytic activities were investigated in the synthesis of quinoline. It was shown that catalytic activities of these catalysts correlated to surface acidity and total number of acidic sites. Finally, a series of quinoline derivatives were synthesized with Cs2.5H0.5PW12O40 via the Friedländer reaction in high to excellent yields and the plausible mechanism was proposed. Simple experiment, catalyst reusability, short reaction time and preclusion of toxic solvent are the advantages of this method.