Advances in Synthetic Strategies for Coumarins and Analogues via Sustainable Chemistry

Abstract:: Coumarins and their analogues are important biologically active heterocycles and have received considerable attention from the scientific community due to their myriad of interesting applications in multidisciplinary areas such as medicinal chemistry, material science, agrochemicals, and photochemistry. Because of the diverse biological and pharmacological properties of coumarin and its annealed derivatives, including anticancer, antiviral, antibacterial, antiinflammatory, antioxidant and enzyme inhibitory activities, synthesizing them has become an urgent research topic in the current context. Several synthetic methodologies for coumarins have been reported. However, many of them are expensive, require toxic reagents, and harsh reaction conditions which limit their synthetic utility in organic synthesis. The increasing concern for environmental sustainability has encouraged the advancement of green technologies for the synthesis of coumarins. This review provides an in-depth study of the recent advances in sustainable synthetic strategies for coumarins and their analogues, with a special emphasis on ultrasonic irradiation, microwave irradiation, ionic liquids, solvent-free conditions, reusable catalytic systems, and room temperature mediated synthesis. These green and sustainable reaction strategies enhance reaction efficiency, product yield, product selectivity, and significantly reduce reaction time, energy consumption, and environmental footprint compared to traditional methods. In addition, some important post-synthetic applications of coumarins are also included, which can lead to successful synthesis of important heterocyclic compounds such as benzocoumarin, indolocoumarin, furocoumarin, pyranocoumarin, pyridocoumarin, pyrrolocoumarin etc. Overall, this review aims to provide synthetic chemists and researchers with an updated and systematic account of environmentally benign techniques that contribute to the eco-friendly synthetic development of coumarin chemistry.