Deep eutectic solvents (DESs), also known as deep eutectic ionic liquids (DEILs) or low-melting mixtures (LMMs) or low transition temperature mixtures (LTTMs) in the literature, have become more and more attractive in recent years due to their interesting properties and benefits, such as low cost of components, easy to prepare, tunable physicochemical properties, negligible vapor pressure, non-toxicity, biorenewability and biodegradability. These eutectic mixtures have been widely used as green and sustainable media as well as catalysts in many chemical processes. This review focuses on recent advances using DESs in organic reactions including addition reactions, cyclization reactions, replacement reactions, multicomponent reactions, condensation reactions, oxidation reactions, and reducing reactions.

A simple, facile and convenient strategy has been developed for the synthesis of dihydropyrimidine‐5‐carboxamides in low melting mixture of betaine hydrochloride/urea. In this procedure, the low melting mixture of betaine hydrochloride/urea plays a triple role: as a catalyst, solvent and reactant. The present green protocol has advantages such as high yield of products, short reaction times, operational simplicity, no chromatographic separation, eco‐friendliness, and applicability for large‐scale synthesis.

Choline chloride and itaconic acid-based deep eutectic solvent has been identified as an effective catalyst and reaction medium for synthesis of 13-aryl-5H-dibenzo[b,i]xanthene-5,7,12,14(13H)-tetraones by condensation of 2-hydroxynaphthalene-1,4-dione with various aldehydes. The reaction conditions are mild and environmentally friendly. Graphical abstract RCHO O O OH O O O O O R ChCl/itaconic acid + 2 80 o C

The title compounds are prepared by metal‐free condensation of hydroxynaphthalenedione with various aromatic aldehydes using choline chloride/itaconic acid as efficient catalyst and reaction medium.

A new, environment‐friendly protocol is described for the synthesis of dihydropyrimidine‐5‐carboxamides in a low‐melting deep eutectic solvent from a mixture of betaine hydrochloride with urea.