Search

The use of volatile solvents for organic synthesis is nowadays questioned due to their negative impact on the environnement. To develop sustainable and environmentally friendly methodologies, we propose to combine two green chemistry concepts: the use of bioinspired solvents: natural deep eutectic solvents (NaDES), and mechanochemistry. Using the Suzuki‐Miyaura coupling as a model reaction, we described an efficient mechanochemical method with NaDES as a LAG (liquid‐assisted grinding) additive with short reaction times and without any ligand or additional heating. A mechanochemical extraction was also used to reduce the amounts of extraction solvents and the total time of the synthesis process. [ABSTRACT FROM AUTHOR]

In recent years, there has been an increasing tendency to use biocatalysts in industrial chemistry, especially in the pharma and fine chemical sector. Preferably, enzymes or whole cells, applied as catalysts for a specific biotransformation, are utilized in aqueous reaction media since water is the natural medium for enzymes. In numerous examples of biocatalytic systems, however, a major problem is the insolubility of hydrophobic substrates in such aqueous reaction media. Apart from lipases, many enzymes are highly sensitive to organic solvents and are inactivated by an organic medium. Therefore, a change of solvent for biotransformations from water to organic solvents is usually challenging. In this study, we investigated the synthesis of nitriles by an organic solvent‐labile aldoxime dehydratase in pure organic solvents, exemplified for the dehydration of n‐octanaloxime to n‐octanenitrile. We present a method for applications in batch as well as flow mode based on an "immobilized aqueous phase" bearing the whole cells in a superabsorber as solid phase, thus enabling the use of a purely organic solvent as "mobile phase" and reaction medium. [ABSTRACT FROM AUTHOR]

Organic synthesis without an organic solvent is still the exception. In this microreview, we discuss and compare different synthetic methods that proceed in the absence of conventional organic solvents. This includes solvent‐free methods in solids (mechanochemistry and solid‐state photochemistry), and in neat liquids (thermal and photocatalytic), as well as the application of unconventional solvents, such as ionic liquids and deep‐eutectic solvents. The different approaches are briefly introduced and examples illustrate their specific advantages, followed by a critical discussion of their limitations. Some methods have the intrinsic benefits of solvent‐free operation, such as avoiding solubility problems and side‐reactions with the solvent. However, every method has specific advantages and the demand of the synthetic application is crucial for selecting the best technique. [ABSTRACT FROM AUTHOR]

This microreview summarizes the use of deep eutectic solvents (DESs) and related melts in organic synthesis. Solvents of this type combine the great advantages of other proposed environmentally benign alternative solvents, such as low toxicity, high availability, low inflammability, high recyclability, low volatility, and low price, avoiding many disadvantages of the more modern media. The fact that many of the components of these mixtures come directly from nature assures their biodegradability and renewability. The classification and distribution of the reactions into different sections in this microreview, as well as the emphasis paid to their scope, easily allow a general reader to understand the actual state of the art and the great opportunities opened, not only for academic purposes but also for industry. [ABSTRACT FROM AUTHOR]