Cooperative Education in Green Chemistry: The Spanish Experience

A common postgraduate training in Green Chemistry is currently being carried out by several Spanish universities. This initiative considers the corresponding Máster and PhD programs in Sustainable Chemistry and has been successfully achieved with the participation of experts from different Universities and Research Institutions grouped within the coverage of the Spanish Network on Sustainable Chemistry (REDQS). A cooperative effort and a modular design are the key elements that have allowed maintaining the Spanish Interuniversity Máster and PhD programs for more than a decade, providing a high level of quality and a unique possibility, for many students, of being trained at an advanced level in Green Chemistry

Chiral catalysts immobilized on achiral polymers: effect of the polymer support on the performance of the catalyst

Positive effects of the polymeric support on the performance of supported chiral catalysts, in terms of activity, stability and selectivity–enantioselectivity, have been reported when the support is properly selected and optimized opening the way to the design of more efficient catalytic systems

Imidazolium based gemini amphiphiles derived from L-valine. Structural elements and surfactant properties

Imidazolium amphiphiles often display excellent surfactants properties, while amide functionalities and chirality can implement self-assembly. The introduction of these functionalities in imidazolium gemini amphiphiles is expected to allow tuning their aggregation, achieving a higher emulsifying capacity of interest for practical applications. L-valine-derived gemini surfactants have been prepared and their aggregation investigated using NMR, UV-CD, fluorescence, LS or microscopy. The imidazolium gemini amphiphiles synthetized, presented excellent surfactant properties. The aromatic substitution pattern defines additional geometric constrains facilitating a fine tune of their properties, displaying the para-substituted compound best properties. This can be associated to facilitating the required conformational organization of polar and apolar fragments, while reducing coulombic repulsions between imizadolium rings. Two critical aggregation concentrations (CACs) were observed by fluorescence in aqueous media, with the formation of well-defined vesicles in the second step. Dynamic equilibria between aggregates of different sizes seem to be present. These gemini surfactants revealed of interest as emulsifiers for oil/water systems and for controlled fragrance delivery using (R)-limonene as a benchmark volatile compound. (C) 2021 Elsevier B.V. All rights reserved.Peer reviewe

Open chain pseudopeptides as hydrogelators with reversible and dynamic responsiveness to pH, temperature and sonication as vehicles for controlled drug delivery

A new family of open chain-pseudopeptidic compounds displaying a pendant carboxylic group have been prepared with excellent yields. Their self-assembly has been studied under different conditions and in different media. Some of the compounds obtained have revealed to act as very efficient hydrogelators at low concentrations (CGC 1 mg mL−1). The resulting hydrogels show some interesting properties, including a high thermal stability, with the hydrogels maintaining their structure at temperatures above 65 °C, and their reversible dynamic sol–gel behavior being responsive to thermal and sonochemical inputs and to changes in the basic/acidic properties of the medium. Preliminary studies for controlled drug delivery have been carried out using a Franz Cell and employing a skin pig membrane, confirming that these Low Molecular Weight Gelators (LMWGs) can be appropriate vehicles for the controlled transdermal delivery of small-molecule drugs.Funding for open access charge: CRUE-Universitat Jaume

Cu2+ recognition by N,N′-benzylated bis(amino amides)

Two new C 2 -symmetric N , N ’ -benzylated bis(amino amides) have been synthesised and their interaction with di ff erent transition metals studied using a variety of techniques including UV-Vis and CD spec- troscopy or ESI-MS. The determination of the corresponding stability constants with Cu 2+ has been possi- ble, in H 2 O/CH 3 CN 7/3 v/v, for one of these ligands ( 4 ) using potentiometric titrations. The results obtained reveal that N -benzylation a ff ords signi fi cant changes to their properties and is accompanied by an appreciable decrease in the corresponding complexation stability constants. However, this, along with the low kinetics associated to Ni 2+ , facilitates the recognition of Cu 2+ by 4 that can be followed by the naked-eye up to the submillimolar range. Very interestingly, the chiral nature of this ligand provides an intense and well de fi ned CD curve for the corresponding Cu 2+ complex, very sensitive to the coordination geometry, facilitating the analysis of this interaction even at the μ M range. The formation by both ligands ( 3 and 4 ) of square planar complexes with Cu 2+ and Ni 2+ displaying a 1 : 1 stoichiometry was con fi rmed by their X-ray crystal structuresFinancial support from Spanish MINECO (CTQ2015-68429-R), Generalitat Valenciana (PROMETEO/2016/071) and PPI-UJI (P1-1B-2013-38) is gratefully acknowledged. L. G. thanks Generalitat Valenciana for a Grisolia fellowship (GRISOLIA 2012/015)

Ionic liquids and continuous flow processes: a good marriage to design sustainable processes

In the last few years the use of Ionic Liquids (ILs) as alternative solvents for (bio)catalytic processes has increased substantially, and the benefits and different approaches reported to combine continuous flow systems and ILs are at the core of this overview. The synergy between both elements allowed us to highlight their great potential in manufacturing both bulk and fine chemicals by new and greener (bio)catalytic processesThis work was partially supported by MINECO, Spain (Ref: CTQ2011-28903) and Generalitat Valenciana (PROMETEO 2012/020) and UJI (P1-1B 2013-37

Preparation of nanofibers mats derived from task-specific polymeric ionic liquid for sensing and catalytic applications

Nanofibers mats derived from the task-specific functionalized polymeric ionic liquids based on homocysteine thiolactone are obtained by electrospinning them as blends with polyvinylpyrrolidone. The presence of this functional moiety allowed the post-functionalization of these mats through the aminolysis of the thiolactone ring in the presence of an amine by a thiol–alkene “click” reaction. Under controlled experimental conditions the modification can be performed introducing different functionalization and crosslinking of the electrospun fibers, while maintaining the nanostructure obtained by the electrospinning. Initial studies suggest that the nanofibers based on these functionalized polymeric ionic liquids can be used in both sensing and catalytic applications

Chiral imidazolium prolinate salts as efficient synzymatic organocatalysts for the asymmetric aldol reaction

Chiral imidazolium l-prolinate salts, providing a complex network of supramolecular interaction in a chiral environment, have been studied as synzymatic catalytic systems. They are demonstrated to be green and efficient chiral organocatalysts for direct asymmetric aldol reactions at room temperature. The corresponding aldol products were obtained with moderate to good enantioselectivities. The influence of the presence of chirality in both the imidazolium cation and the prolinate anion on the transfer of chirality from the organocatalyst to the aldol product has been studied. Moreover, interesting match/mismatch situations have been observed regarding configuration of chirality of the two components through the analysis of results for organocatalysts derived from both enantiomers of prolinate (R/S) and the trans/cis isomers for the chiral fragment of the cation. This is associated with differences in the corresponding reaction rates but also to the different tendencies for the formation of aggregates, as evidenced by nonlinear effects studies (NLE). Excellent activities, selectivities, and enantioselectivities could be achieved by an appropriate selection of the structural elements at the cation and anion

Highly Selective Anion Template Effect in the Synthesis of Constrained Pseudopeptidic Macrocyclic Cyclophanes

Herein, we report the synthesis of a novel family of constrained pseudopeptidic macrocyclic compounds containing the hexahydropyrrolo[3,4-f]isoindolocyclophane scaffold and involving four coupled substitution reactions in the macrocyclization process. Although the increase in the number of steps involved in the macrocyclization could lead to a larger number of possible side products, the optimization of the methodology and the study of the driving forces have made it possible to obtain the desired macrocycles in excellent yields. A thorough computational study has been carried out to understand the macrocyclization process, and the results obtained nicely agree with experimental data. Moreover, the bromide anion had a clear catalytic template effect in the macrocyclization reaction, and surprisingly, the chloride anion had a negative template effect in opposition to the results obtained for analogous macrocycles. The parameters responsible for the specific kinetic template effect observed have been studied in detail

Pseudopeptidic Macrocycles as Cooperative Minimalistic Synzyme Systems for the Remarkable Activation and Conversion of CO2 in the Presence of Chloride Anion

A series of pseudopeptidic compounds have been assayed as organocatalyts for the conversion of CO2 into organic car-bonates through a cooperative multifunctional mechanism. Conformationally constrained pseudopeptidic macrocycles 3a and 3b have revealed to be excellent synzymes for this purpose, being able to provide a suitable preorganization of the different functional elements and reaction components to activate the CO2 molecule and stabilize the different anionic intermediates involved, through a series of cooperative supramolecular interactions. As a result, remarkable catalytic efficiencies are found at low CO2 pressures and moderate temperatures, with TON and TOF values surpassing those reported for other organocatalytic supramolecular systems under similar conditions. The process works well for monosubstituted epoxides. The involvement of the different structural elements has been analyzed in detail and preliminary studies show the potential for recovering and reuse of these catalytic systems