Deep eutectic solvents and their applications as green solvents

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.