Abstract:
Coumarin and its derivatives are privileged heterocyclic motifs and important building
blocks for developing the biologically active compound due to its significant role in the development
of new drugs. As a result, many methodologies have been developed to synthesize this important
class of compounds. However, some methods are associated with toxic and corrosive catalysts, longer
reaction time, poor yield, less purity, and by-products along with the desired product. In order to minimize the utilization and generation of toxic organic substances, green synthetic methods are applied
in this manner. Green chemistry methods cover a wide range of methods, including the application of
ultrasound and microwaves, ionic liquids and deep eutectic solvents, solvent-free and catalyst-free
synthesis, and mechanosynthesis. These green synthetic methods have successfully performed all typical condensation reactions for coumarin synthesis like Knoevenagel, Perkin, Kostanecki-Robinson,
Pechmann, and Reformatsky reactions. Compared to conventional methods, these methods not only
minimize the use and generation of harmful chemicals but also improve reaction efficiency in terms
of product yields, purity, energy consumption, and post-synthetic procedures. Due to the implication
of coumarin (2-oxo-2H-1-benzopyran) backbone as a biologically active ubiquitous fragment and the
recent demands of reducing toxic solvents, catalysts, and energy consumption, this review summarized various green synthetic methods for coumarin synthesis. Moreover, researchers working on this
coumarin scaffold synthesis can find handy information from this review on the green synthetic approaches to their synthesis.