África joven: arte y diáspora

Este artículo es fruto de una experiencia interuniversitaria, internacional y transdisciplinar, llevada a cabo el curso 2021-2022 en la Universidad de Lleida con la colaboración de la Universidad de Zaragoza, en la que participaron también otros colectivos e instituciones, sobre África Joven: arte y diáspora. En ella se llevaron a cabo dos Seminarios, un Seminario teórico-práctico con alumnado del Grado de Educación Social sobre el objeto artístico negroafricano como referencia del pluralismo cultural, y un Seminario Internacional con tres ponencias sobre arte, resiliencia y rehumanización donde se trató de la música, el baile y la oralidad como terapia resiliente en las tradiciones africanas y afrodiaspóricas; además, una iniciativa sobre el Top Manta, que es la marca del proyecto comercial del Sindicato Mantero y, por último, una propuesta práctica para intervenir desde el contexto artístico en colectivos en riesgo, es decir, se realizaron tres propuestas combinadas con una exposición sobre Máscaras negroafricanas titulada "Aprender a ver lo invisible"

Highly efficient Tsuji–Trost allylation in water catalyzed by Pd-nanoparticles

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On the macrocyclization selectivity of meta-substituted diamines and dialdehydes: towards macrocycles with tunable functional peripheries

Abstract: The efficient preparation of functional rigid and soluble macrocycles remains a challenge for synthetic chemists. Here, we exploit the thermodynamic control of dynamic covalent chemistry to investigate the influence of the monomer structure on the macrocyclization selectivity. A series of rigid cyclic hexamer has been synthesized by imine condensation of benzene building blocks, i.e. meta-substituted diamines and dialdehydes, templated by calcium(II) chloride. The monomers were designed to feature various additional functional groups either available for further post-cyclization modifications or acting as solubilizing groups. The cyclization selectivity was systematically investigated and optimized depending on the length of the applied solubilizing group and on the nature of the additional functional group. A selectivity up to 92% was reached for the macrocyclization exhibiting trifluoromethyl and bromine groups at the outer periphery and hydroxyl groups in the cavity. Graphic abstract: [Figure not available: see fulltext.].</p

Sustainable succinylation of cellulose in a CO 2 -based switchable solvent and subsequent Passerini 3-CR and Ugi 4-CR modification

A rapid and effective dissolution and activation of cellulose was demonstrated by a reversible reaction of CO2 with the hydroxyl groups of the cellulose backbone in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). The obtained carbonate complex of cellulose was subsequently subjected to in situ derivatization with succinic anhydride without the need of any additional catalyst under very mild conditions. As a result of optimization studies, cellulose was succesfully converted to cellulose succinates with degrees of substitution (DS) ranging from 1.51 to 2.64, depending on the reaction conditions and the molar ratio of succinic anhydride. The optimized reaction conditions were successfully applied to different types of cellulose samples including microcrystalline cellulose (MCC) and organosolv wood pulp (WP), exhibiting similar conversions. Furthermore, the carboxylic acid moiety, introduced by the succinylation, was further converted via Passerini three-component reactions (Passerini-3CR) and Ugi four-component reactions (Ugi-4CR). 31 P NMR revealed the quantitative conversions of carboxylic acid moieties on the cellulose backbone under mild conditions. The obtained products were thoroughly characterized by ATR-IR, 1 H, 13 C, and 31 P NMR spectroscopies as well as by gel permeation chromatography (GPC). Thermal properties of the obtained products were investigated by differential scanning calorimetry (DSC) and by thermogravimetric analysis (TGA), revealing glass transitions (Tg) for all the Passerini and Ugi products between 76-116 °C and high thermal stability between 263-290 °C. The reported methodology represents a very mild, highly efficient and sustainable route for the dissolution of cellulose and the synthesis of cellulose succinates. The subsequent modifications of the obtained cellulose succinates via multicomponent reactions resulted in materials with improved thermal properties and offers a straightforward and versatile modification strategy for cellulose