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

<p>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.