Classical Approaches and Their Creative Advances in the Synthesis of Coumarins: A Brief Review

Coumarin chemical nucleus is a gift awarded from nature to humanity. The multifarious derivatives and the broad range of their bio-medicinal potentials are the basis for this description. In the last several decades, though numerous coumarin-based products have been primarily separated from their biological origins, the laboratory synthesis of the coumarins is developing. Various synthetic trails namely Knoevenagel, Claisen, Perkin, Pechmann, Wittig, and Reformatsky have been reported. Several advanced innovations have been created to maximize yield, minimize overall reaction time, avoid side products, and make synthetic reactions environmentally friendly. These include the employment of ultrasonic, microwave, and solvent-free conditions. This brief review focuses on the classic methods for synthesizing coumarins, and the advantages derived from the use of creative catalytic tools.