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 2‐aminoaryl aldehyde or ketone and an aldehyde or ketone containing an α‐ methylene group. This procedure has been catalyzed by several homogeneous and heterogeneous catalysts, such as bases, Brönsted acids, Lewis acids, ionic liquids, etc. Keywords: Quinoline, Friedländer synthesis, 2-aminobenzophenone, carbonyl compounds, one-pot, multi-component reactions.