Recent advances in the application of deep eutectic solvents for the synthesis of Spiro heterocyclic scaffolds via multicomponent reactions

Deep eutectic solvents (DESs) consist of liquid mixtures of solid components and complexing agents as a hydrogen bond donor (eutectic combinations of Lewis or Bronsted acids and bases) at room temperature, which is a reliable, sustainable, safe, and significant alternative to conventional and common volatile and toxic solvents in green organic synthesis that have tunable physicochemical properties. The advantages of these solvents include their low toxicity, recoverability, ultra-solvent capacity, negligible flammability, easy reusability, high biodegradation, low volatile organic compound character, tunable polarity, and low flammability. As a result, these solvents have opened up a revolutionary era in green chemistry, motivating all chemists to protect the environment. In the field of organic chemistry and medicinal research, MCR has been a valuable synthetic strategy method thanks to its high yields, regioselectivity, and short reaction times. Over the last decade, Spiro cyclic skeletons have gained widespread recognition due to their pharmacological properties as well as potential biological activities. Accordingly, this review will briefly discuss and highlight recent research progress on the synergistic effect of the combined use of MCRs and DESs for developing novel eco-friendly methodologies aimed at synthesizing various Spiro heterocyclic compounds through multicomponent reactions using deep eutectic solvents between 2015 and 2022.