Recent progress in the synthesis of imidazoquinoline derivatives

Heterocyclic compounds, ubiquitous in nature and on the synthetic scale, are crucial as they acquire a wide spectrum of significant pharmacological properties. Imidazoquinolines, formed by the annulation of imidazole and quinoline rings dominated drug design and development. Imidazoquinoline hybrids have an extensive range of biological applications such as antiviral, antifungal, anticancer, antibacterial, antiallergic, antioxidant, antithrombotic, as agonists of various toll-like and 5-HT_1A receptors to treat various CNS disorders, and as inhibitors of phosphoinositide 3-kinases and cholinesterases. This review article explores multiple synthetic approaches for the preparation of imidazoquinoline isomers, including multicomponent, microwave-assisted, iodine-mediated, electrochemical, electrocatalytic tandem techniques, sequential Heck and oxidative amination reactions, cycloaddition and aza-Michael addition reactions, copper-mediated aerobic three-component cyclization reactions, copper-assisted double oxidative CH amination and halogenation, oxidative annulation reactions and Suzuki cross-coupling reactions.