4‐Hydroxycoumarin: A Versatile Substrate for Transition‐metal‐free Multicomponent Synthesis of Bioactive Heterocycles

Abstract

Abstract One‐pot multi‐component reactions especially under transition‐metal‐free catalysis served as an efficient, and environmentally friendly method for the construction of value‐added compounds. Their importance in organic synthesis has drastically increased due to their operational simplicity, cost‐effectiveness, step‐ and pot‐economic nature. On the other hand, the molecular hybridization concept has recently emerged as a key fascinating area in medicinal and organic chemistry for the design of new drugs. Owing to the widespread occurrence in natural products, and pharmaceutical agents, the incorporation of another heterocycle either as substituents or as a fused material into 4‐hydroxycoumarin moiety offers new opportunities for the broad application of the targeted coumarin‐heterocycles into many branches of chemistry. Considering the importance of both the topics, here we have reviewed the developments achieved in the synthesis of diverse medicinally privileged oxygen, and nitrogen‐containing heterocycles as well as spiro‐heterocycles either linked or fused with coumarin moiety by using readily accessible 4‐hydroxycoumarin as the starting material via one‐pot multi‐component reaction under transition‐metal‐free conditions.