Recent Advances in Copper-catalyzed Heterocyclic Syntheses

Heterocycles have gained significant attention from the research community due to their prevalence in numerous natural products and their applications as pharmaceuticals, agrochemicals, and new materials. The application of transition metal catalysts in the synthesis of heterocyclic compounds is an indispensable tool in the field of organic synthesis and has acquired notable recognition in scientific society all over the world. The popularity of copper-based catalysts is attributed to their costeffectiveness, easy accessibility, and environmentally benign nature. In addition to this, the ability of copper catalysts to coordinate with heteroatoms and to activate unsaturated systems has resulted in the growing interest of synthetic and medicinal chemists in this field. Copper-based catalysts have shown their application in various cross-coupling reactions, C–H functionalization, radical alkylations, conjugate additions, and trifluoromethylation. Furthermore, they have also exhibited tremendous scope in heterocyclic syntheses, which include many important reactions, such as azide-alkyne click reaction (a type of 1,3-dipolar cycloaddition), nitrone-olefin cycloaddition (Kinugasa reaction), multi-component reactions, and other similar strategies which result in the construction of 4-8 membered heterocyclic adducts of biological and industrial relevance. The copper-catalyzed heterocyclic syntheses have many advantages, such as easily accessible substrates, good atom economy, high functional group tolerance, excellent yields, and remarkable selectivities. In addition to this, the targetted heterocycles exhibited diverse biological activities viz. antibacterial, antifungal, anticancer, antitubercular, anti-HIV, anti-inflammatory, analgesics, and antiviral activities. The main aim of this chapter is to summarize the advances made in copper-catalyzed synthesis of heterocyclic compounds in the last ten years.