Highly efficient Brønsted acid and Lewis acid catalysis systems for the Friedländer Quinoline synthesis

The efficient and green Brønsted acid or Lewis acid catalysis systems for the Friedländer synthesis of 2,3,4-trisubstituted quinolines from the condensation of 2-aminoarylketones and β-ketoesters/ketones had been developed. The results confirmed that 4-toluenesulfonic acid, magnesium chloride, and cupric nitrate were the desired catalyst independently. This protocol had the advantages of mild conditions, operational simplicity, and excellent yields.