Deep eutectic solvents and their applications as green solvents

Abstract

Several examples illustrate the effectiveness of using Deep Eutectic Solvents (DESs) as environmentally responsible reaction media in polar organometallic chemistry and in metal-catalysed and biocatalysed processes in place of conventional, often hazardous volatile organic compounds (VOCs). Apart from the standpoint of ‘greenness’, applications of DESs in the aforementioned fields also reveal novel aspects of reactivity of practical significance, which are worthy of an in-depth mechanistic understanding: (a) metal-mediated organic transformations can be run in DESs competitively with protonolysis, often at room temperature and under air, (b) metal-catalysed reactions proceed efficiently and under milder conditions in DESs than in VOCs, with the catalyst and DES being easily and successfully recycled and (c) biocatalysts often exhibit higher stability, selectivity and performances in DES mixtures than in aqueous solutions, as well as a somewhat intriguing stereoselectivity. • Main-group metal–mediated organic synthesis can be run under air and at room temperature in Deep Eutectic Solvents (DESs). • Metal-catalysed reactions in DESs take place under milder conditions than in traditional volatile organic compounds. • The use of eutectic mixtures often allows an efficient recycling of both the catalyst and the solvent. • DESs represent alternative and effective reaction media to water in biochemical processes. • Isolated enzymes and whole-cells often exhibit higher performance and stability in DESs.