Recent advances in green and traditional synthetic approaches for coumarin derivatives: a comprehensive review

Coumarins are a class of naturally occurring six-membered heterocyclic compounds widely recognized for their diverse pharmacological activities, making them a highly versatile entity in medicine, cosmetics, and the food industry. The biological efficacy of coumarins is intricately linked to their substitution patterns and structural modifications, underscoring the importance of developing efficient synthetic strategies for their derivatives. This review emphasizes green synthetic routes to coumarin derivatives, including microwave-assisted (MW) protocols, ultrasound-assisted methods, heterogeneous and nanocomposite catalyst-supported approaches, solvent-free syntheses, the use of greener solvents such as ionic liquids, and simple grinding techniques. In parallel, we presented conventional synthetic approaches, such as Von Pechmann, Perkins, alkylation, and acylation reactions, as well as multi-component reactions using various catalysts and solvent conditions, for the synthesis of different coumarins. The compilation integrates various schemes that illustrate these methodologies, thereby providing a consolidated perspective on both classical and sustainable approaches to the synthesis of coumarin derivatives of biological relevance.