Critical Assessment of the Sustainability of Deep Eutectic Solvents: A Case Study on Six Choline Chloride-Based Mixtures.

An outline of the advantages, in terms of sustainability, of Deep Eutectic Solvents (DESs) is provided, by analyzing some of the most popular DESs, obtained by the combination of choline chloride, as a hydrogen bond acceptor, and six hydrogen bond donors. The analysis is articulated into four main issues related to sustainability, which are recurrently mentioned in the literature, but are often taken for granted without any further critical elaboration, as the prominent green features of DESs: their low toxicity, good biodegradability, renewable sourcing, and low cost. This contribution is intended to provide a more tangible, evidence-based evaluation of the actual green credentials of the considered DESs, to reinforce or question their supposed sustainability, also in mutual comparison with one another.

Design of a New Chiral Deep Eutectic Solvent Based on 3-Amino-1,2-propanediol and Its Application in Organolithium Chemistry.

A chiral glycerol derivative, namely 3-amino-1,2-propanediol, was employed for as the hydrogen bond donor (HBD) in the design of a new deep eutectic solvent (DES) with choline chloride acting as the hydrogen bond acceptor (HBA). The novel mixture was characterized and unambiguously classified as a DES. Furthermore, its synthetic usefulness was demonstrated in the room-temperature -butyllithium-addition under air to carbonyl compounds and benzyl chloride.

Ullmann homocoupling of arenediazonium salts in a deep eutectic solvent. Synthetic and mechanistic aspects.

A deep eutectic solvent (DES) based on glycerol and KF is successfully exploited as a solvent medium in Ullmann homocoupling of arenediazonium salts. The reactions were carried out in mild conditions and target products were obtained in fairly good yields. A computational study is presented aiming to understand the reaction mechanism and Raman spectroscopy is employed as an experimental tool to support it.

Silica gel-immobilised chiral 1,2-benzenedisulfonimide: a Brønsted acid heterogeneous catalyst for enantioselective multicomponent Passerini reaction.

A chiral heterogeneous catalyst derivative of (-)-4,5-dimethyl-3,6-bis(1-naphthyl)-1,2-benzenedisulfonimide is proven here to be efficient in a three-component asymmetric Passerini protocol, carried out in a deep eutectic solvent. Reaction conditions are mild and green, while enantioselectivity is excellent. The catalyst was easily recovered and reused with no decrease in its catalytic activity.

Chemo- and Regioselective Anionic Fries Rearrangement Promoted by Lithium Amides under Aerobic Conditions in Sustainable Reaction Media.

A straightforward and efficient protocol to promote the metalation/anionic Fries rearrangements of O-aryl carbamates, using for the first time a lithium amide as metalating agent under aerobic/ambient-friendly reaction conditions, is reported. This approach enables the sustainable preparation of salicylamide derivatives with high levels of chemoselectivity within ultrafast reaction times, working at room temperature in the presence of air/moisture, and using environmentally responsible cyclopentyl methyl ether as a solvent. Furthermore, the regioselective manipulation of O-2-tolyl carbamates has been accomplished using interchangeably alkyllithiums or lithium amides, with an unexpected beneficial contribution from the employment of biorenewable protic eutectic mixtures as non-innocent reaction media.