Sustainable approaches towards the synthesis of quinoxalines: An update

Heterocycles and their derivatives have been inspiring medicinal chemists to device novel, greener and efficient ways to synthesized them as the majority of drugs available in the market contain heterocyclic scaffolds. Therefore, it is highly recommendable for a medicinal chemist to develop more effective and economical methods of synthesis for the privileged heterocyclic scaffolds to meet the quest of greener and sustainable chemistry. Among these, quinoxaline has been found among the plethora of bioactives having unique physicochemical and biological importance. For the synthetic construction of quinoxalines, the newer and novel synthetic methodologies have been accomplished by synthetic organic/medicinal chemists. The present review focuses on the systematic classification of synthetic strategies reported since 2014, focusing on the sustainable and environmentally benign approaches for the synthesis of quinoxalines including solvent-free reactions, use of alternate reaction media (e.g., water, fluorous alcohols, microwave, polyethylene glycols, and ionic liquids), along with some non-energy efficient yet sustainable methodologies.