Regarding all the green aspects of sustainable chemical transformations, eco-friendly processes along with economic development, environmental protection as well as natural resources preservation are mandatory. The use of unconventional media for organic transformations has been part of the quest for new eco-friendly process. As new alternative media for volatile organic solvents, deep eutectic solvents (DES) can be defined as the eutectic mixtures formed of two or more phase-immiscible components, which furnish a new homogeneous liquid phase with lower freezing point than those observed for individual counterparts. They found applications in several different fields, such as solvent/catalyst for organic transformations, biotransformations, and polymerization reactions, metal and biomass processing applications, and separation technologies. This review describes the recent studies on the use of deep eutectic mixtures as solvent and/or catalyst for multicomponent reactions in the synthesis of complex organic compounds.

The indan ring system is present in several compounds with important pharmacological properties. In this account recent examples of selected methods (Friedel-Crafts acylation, cycloaddition reactions, ring contraction, cyclization and resolution) for the synthesis of indans are discussed.