Towards Green Reductions in Bio‐Derived Solvents

Abstract

The hydrogenation processes, and all the reactions that formally add two hydrogen atoms to an unsaturated bond, are among the most used transformations in the manufacture of bulk and fine chemicals. Although their potential as powerful tool for the sustainable synthesis of organic compounds, hydrogenations, and more generally the reductions, have been typically carried out in volatile organic solvents deriving from petroleum; indeed, all studies and fascinating advances related to the catalysts’ activity or the reducing agents’ reactivity have been limited to such volatile and often toxic reaction media. In this review, recent advances in the reducing methodologies with an improved degree of sustainability have been described. In particular, a series of examples have been reported to highlight the chance to reduce an organic compound by using a benign solvent deriving from renewable sources, without waiving to the process efficiency and selectivity. Some important key points of green chemistry, such as the easiness of catalyst recovery or the simplicity of product isolation, have been considered in the choice of the described studies.

5-(4-Chlorophenyl)-N,1-di-o-tolyl-1H-imidazole-2-amine

“…In accordance with our research interests, focused on the development of sustainable synthetic methodologies [18][19][20][21][22][23], in this manuscript we report the preparation of the novel 5-(4-chlorophenyl)-N,1-di-o-tolyl-1H-imidazole-2-amine (3) in a ChCl/urea eutectic mixture as a sustainable reaction medium. The reported methodology is characterized by green and eco-friendly conditions as it employed a bio-inspired and easily recyclable DES, mild reaction settings (under air, 80 • C), and metal-free conditions.…”

Sustainable Green Extraction of Carotenoid Pigments: Innovative Technologies and Bio-Based Solvents

“…However, bio-based solvents also have some disadvantages, mainly related to the cost of production, which can be higher than that of other traditional solvents due to the higher cost of sourcing and processing renewable biomass [62,63]. The use of bio-based solvents for the extraction of carotenoids has been broadly studied and, overall, offers several advantages over petroleum-derived solvents in terms of environment [64]. The following bio-based solvents that have been used to extract carotenoids will be evaluated in this review: ethyl lactate, 2-methyltetrahydrofuran (2-MeTHF), natural deep eutectic solvents (NaDESs), deep eutectic solvents (DESs), and ionic liquids (ILs) (Figure 2).…”

Transition‐Metal‐Catalysed Transfer Hydrogenation Reactions with Glycerol and Carbohydrates as Hydrogen Donors

“… [42–45] Due to its unique properties, such as high boiling point, low toxicity, non‐volatile, biodegradable and high polarity, glycerol is considered a green solvent in organic synthesis [46,47] . Moreover, glycerol is used as a renewable hydrogen donor to reduce various functional groups in the presence of transition metal catalysts [33] . This section will discuss TH reactions of various substrates with glycerol as a hydrogen donor using homogeneous and heterogeneous catalytic systems.…”