Biheterocyclic Coumarins: A Simple Yet Versatile Resource for Futuristic Design and Applications in Bio-molecular and Material Chemistry

Coumarin derivatives occur widely in nature and are a part of both traditional and modern advancements in synthesis and application. To date, thousands of coumarin derivatives have been synthesized in lab or isolated from plant and marine life. These are essentially 2-pyrone core fused with a benzene ring and belong to the family of aromatic oxygen heterocycles. Coumarin in conjugation with various other heterocyclic systems has provided a robust framework for tuning the properties associated with the parent structure. The frequency of reports has increased for these biheterocyclic systems from the mid twentieth century. Biheterocyclic coumarins have also attracted the attention of many organic and pharmaceutical chemists as these systems serve as useful synthetic intermediates in the synthesis of analogs of existing drugs. Their application in the design of effective organocatalysts and chemosensors has further extended their versatility. Coumarin biheterocyclic core is utilized in the rational design and tuning of complex molecular entities in molecular recognition, analytical and material chemistry. This review highlights the advancements in the synthesis and applications of coumarin-linked nitrogen, oxygen, and sulfur heterocycles. It also provides an account of five-, six-, and seven-membered heterocyclic rings linked to coumarin core. Critical physicochemical properties coupled with their application will make this review useful for synthetic chemists and drug discovery labs. A comprehensive spectrum of literature in this review will facilitate further development of biheterocycles along with their promising applications in the future.