Friedlander Synthesis of Poly-Substituted Quinolines: A Mini Review

Quinolines and their derivatives are an important class of heterocyclic compounds that occur widely in natural products, drugs and biologically active compounds. A large variety of quinolines have displayed interesting physiological activities and found attractive applications as pharmaceuticals and agrochemicals. In accordance with these useful properties and related applications as above-mentioned, a number of methods have been reported for the synthesis of quinolines. Although other methods such as the Skraup, Doebner-Miller and Combes procedures have been reported, the Friedländer heteroannulation is still one of the most simple and straightforward methods used to produce poly-substituted quinolines. The Friedländer synthesis involves a condensation reaction followed by a cyclodehydration reaction between an 2128;aminoaryl aldehyde or ketone and an aldehyde or ketone containing an α128; methylene group. This procedure has been catalyzed by several homogeneous and heterogeneous catalysts, such as bases, Brönsted acids, Lewis acids, ionic liquids, etc.