p-TSA-Based DESs as “Active Green Solvents” for Microwave Enhanced Cyclization of 2-Alkynyl-(hetero)-arylcarboxylates: an Alternative Access to 6-Substituted 3,4-Fused 2-Pyranones

In this paper, we describe the use of p-TSA based Deep Eutectic Solvents (DESs) as alternative environmental-friendly \u201cactive\u201d solvents for the microwave-mediated synthesis of 6-substituted 3,4-fused 2-pyranones, and in particular isocoumarins, starting from 2-alkynyl-(hetero)arylcarboxylates. When the alkyne terminus bears a neutral or an electron-donating group (EDG), the reactions are fast, clean and highly regioselective, to give the 6-endo-dig cyclization products in good to excellent yields. For substrates bearing an electron-withdrawing group (EWG) on the alkyne end, the regioselectivity can be tuned by adding a small amount of silver(I) triflate as co-catalyst. DES was demonstrated to be reusable without loss of efficiency in terms of reaction yields. Based on experimental evidences and previous findings, two competitive mechanisms working simultaneously are proposed to explain the outcomes and the regioselectivity issues

Asymmetric Organocatalysis in Deep Eutectic Solvents

The recent advances in asymmetric organocatalysis using eutectic mixtures as a reaction medium are revised in this mini‐review. In addition, the first enantioselective transformations using chiral eutectic solvents, which play the role of a green medium and organocatalyst, are described. In this mini‐review we intend to deepen not only in the synthetic aspects of asymmetric organocatalysis in eutectic mixtures, but also in the fundamental issues that seem to be essential for a successful development of this promising, and at the same time challenging, methodology.This work was supported by the Spanish Ministerio de Ciencia, Innovación y Universidades (MICINN, PGC2018-096616-B-I00), the University of Alicante (VIGROB-173 and VIGROB-316FI), and the University of Pisa (PRA_2018_36)

Highly recyclable surfactant-based supramolecular eutectogels for iodine removal

In this work, we screened several surfactants for their ability to harden Eutectic Mixtures. We found cetyldiethanolamine-N-oxide as the best candidate, which was able to form eutectogel in four eutectic mixtures. Characterization of the gels obtained in terms of thermal stability, rheology and gelation kinetics, showed a prominent influence of the nature of the hydrogen bonding accepting and donating components for the first two parameter and the other one, respectively. Then, we assessed the eutectogels for their ability to adsorb I2, as a model for its radioactive nuclides, from apolar solvent solutions. The best performing gel allowed fast and thorough removal of I2, over a broad range of initial concentrations. This gel displayed a maximum adsorption capacity of 280 mg/g, competitive with most gel-based sorbent reported in the literature for the adsorption of iodine. Interestingly, the eutectogel proved to be highly recyclable, it could be regenerated and reused without loss in performance

Improved strain sensing properties of cement-based sensors through enhanced carbon nanotube dispersion

New multifunctional materials are under continuous development in various fields of the scientific and technological panorama, due to the enhanced applications they concern. Among these materials, cement-based composites appear particularly noticeable for their real impact on engineering and, in particular, for their use as structural materials. A pioneering application of such multifunctional materials is the monitoring of the stresses and strains of structures during their service conditions by use of embedded cementitious sensors doped with smart conductive fillers, such as carbon nanotubes. The homogeneity of the sensors is essential for their reliability and the dispersion techniques result a delicate task. The paper proposes a novel surfactant dispersion additive for improving conductivity and strain-sensing properties of cement-based sensors (DDA) and compares its behavior with that of conventional ones. Chemical, electrical and electromechanical tests have been carried out to demonstrate the superiority of the proposed surfactant and the resulting improvement in functional properties of the novel cementitious composite material for applications in constructions. The samples with the novel dispersant DDA, developed by the Authors, exhibit higher gauge factors, higher linearity, with reduced drift and hysteresis behavior

Glycosylation reaction using anomeric selenoxides

Oxidation of anomeric selenides, obtained from the radical azido phenylselenenylation of glycals, generates in situ extremely reactive glycosyl donors. When a 2-azido-2-deoxy-1-phenylselenomannoside is treated at a low temperature with perfluoro-cis-2,3-dialkyloxaziridine in the presence of a glycosyl acceptor, a (1-6)-β-linked mannopyranoside is obtained free from its α-isomer. 2-Phenyl-4,5-(3,4,6,-tri-O-methyl-1,2-di-deoxy-β-D-mannopyrano)-[2,1-d]-2-o xazoline, is isolated when 2-benzamido-2-deoxy-1-phenylselenomannoside is allowed to react with m-CPBA in dichloromethane

Effect of water addition on choline chloride/glycol deep eutectic solvents: Characterization of their structural and physicochemical properties

In the present study the effect of water on the physicochemical properties and on the structural features of three deep eutectic solvents (DESs) were evaluated. The DESs are formed by choline chloride (ChCl) and glycols with a different number of oxyethylene units: diethylene glycol (DEG), triethylene glycol (TEG) and poly(ethylene glycol) 200 (PEG 200). From the dilution effect on the physicochemical properties of DESs it has emerged that even a small amount of water could increase fluidity, conductivity and polarity of the DESs. The effect of water addition on the nanostructural changes of DESs was also investigated by FTIR and NMR spectroscopies. The results clearly demonstrated that there are strong interactions between the two components of the DES and dilution with water caused the interactions weaken gradually up to 50% (w/w) water added, but with the supramolecular structures to some extent preserved. Subsequent water additions led to the disappearance of such interactions until they disappeared completely at around 75% (w/w). Moreover, NMR studies showed that the H-bonding interactions between ChCl and DEG are less strong than those between ChCl and both TEG and PEG 200, indicating that the number of oxyethylene units may be important. The changes observed in the physicochemical properties and on the nanostructural features of the mixtures can lead to the realization of liquid designed for tailored applications