Synthesis of Quinolines: A Green Perspective

The quinoline scaffold is present in a vast number of natural compounds and pharmacologically active substances, comprising a significant segment of the pharmaceutical market. The classical methods for the synthesis of this heterocyclic skeleton require the use of expensive starting materials and high temperature conditions. Chemists play a fundamental role in the construction of a sustainable future through the pursuit of greener chemical processes. As so, the development of new synthetic methods using more efficient energy sources and less hazardous solvents as well as renewable and eco-friendly catalysts to attain the quinoline scaffold can provide significant environmental and economic advantages. This review unveils green methods used in the synthesis of quinolones. Important green metrics are calculated for each proposed method and the statistical analysis allowed us to propose the best approaches for further investigation. The applied research is eventually unveiling the full potential of Friedlander and/or multicomponent reactions, to improve atom economy.