Enantioselective Synthesis of Succinimides by Michael Addition of 1,3-Dicarbonyl Compounds to Maleimides Catalyzed by a Chiral Bis(2-aminobenzimidazole) Organocatalyst

A wide variety of chiral succinimides have been prepared in high yields and enantioselectivities by asymmetric conjugate addition of 1,3-dicarbonyl compounds to maleimides under very mild reaction conditions using a bifunctional benzimidazole-derived organocatalyst. Computational and NMR studies support the hydrogen-bonding activation role of the catalyst and the origin of the stereoselectivity of the process.

NHC-Ligand Effectiveness in the Fluorine-Free Hiyama Reaction of Aryl Halides

1-Benzyl-3-(2-hydroxy-2-phenylethyl)imidazolium chloride (5), which is a precursor of an N-heterocyclic carbene ligand, in combination with palladium acetate, has been employed as an effective catalyst for the fluorine-free Hiyama reaction. A systematic study of the catalytic mixture, by a 32 factorial design, has revealed that both the amount of palladium and the Pd/NHC precursor ratio are important factors for obtaining good yields of the coupling products, indicating an interaction between them. The best catalytic system involves mixing 0.1 mol-% palladium acetate in a 1:5 ratio (Pd/salt 5), which allows the effective coupling of a range of aryl bromides and chlorides with trimethoxy(phenyl)silane. The Hiyama reactions are carried out in NaOH solution (50 % H2O w/w), at 120 °C under microwave irradiation during 60 min.

Intramolecular Bromoamination of Conjugated N-Tosylaminodienes Using N-Bromosuccinimide. Synthesis of Bromoallyl-Substituted N-Heterocycles and Their Applications as Building Blocks

The bromonium-promoted cyclization of conjugated aminodienes is described. The reaction proceeds smoothly in the presence of N-bromosuccinimide as halonium promoter, and using N-tosyl-protected aminodienes as substrates, to give the corresponding halocyclization products in high yields and with high diastereoselectivities. It can be envisaged that the formation of these products is the result of an SN2′-type ring-opening of a terminal bromonium intermediate in a 5-exo-trig or 6-exo-trig cyclization mode. The presence of an allyl bromide moiety in the haloamination products makes these molecules highly attractive from a synthetic point of view, as it opens the way for further transformations. Thus, allylic substitution reactions with different nucleophiles (acetate, azide, cyanide, and malonate), palladium-catalysed Suzuki coupling, and silver-mediated bromine displacement reactions were carried out successfully.

1,2-Functionalized Imidazoles as Palladium Ligands: An Efficient and Robust Catalytic System for the Fluorine-Free Hiyama Reaction

A variety of hydroxy- and amino-functionalized imidazoles were prepared from 1-methyl- and 1-(diethoxymethyl)imidazole by means of isoprene-mediated lithiation followed by reaction with an electrophile. These compounds in combination with palladium acetate were screened as catalyst systems for the Hiyama reaction under fluorine-free conditions using microwave irradiation. The systematic study of the catalytic system showed 1-methyl-2-aminoalkylimidazole derivative L1 to be the best ligand, which was employed under solvent-free conditions with a 1:2 Pd/ligand ratio and TBAB (20 mol-%) as additive. The study has revealed an interaction between the Pd/ligand ratio and the amount of TBAB. The established catalytic system presented a certain degree of robustness, and it has been successfully employed in the coupling of a range of aryl bromides and chlorides with different aryl siloxanes. Furthermore, both reagents were employed in an equimolecular amount, without an excess of organosilane.

Pyrimidine-Derived Prolinamides as Recoverable Bifunctional Organocatalysts for Enantioselective Inter- and Intramolecular Aldol Reactions under Solvent-Free Conditions

Chiral L-prolinamides 2 containing the (R,R)- and (S,S)-trans-cyclohexane-1,2-diamine scaffold and a 2-pyrimidinyl unit are synthesized and used as general organocatalysts for intermolecular and intramolecular aldol reactions with 1,6-hexanedioic acid as a co-catalyst under solvent-free conditions. The intermolecular reaction between ketone–aldehyde and aldehyde–aldehyde must be performed under wet conditions with catalyst (S,S)-2b at 10 °C, which affords anti-aldols with high regio-, diastereo-, and enantioselectivities. For the Hajos–Parrish–Eder–Sauer–Wiechert reaction, both diastereomers of catalyst 2 give similar results at room temperature in the absence of water to give the corresponding Wieland–Miescher ketone and derivatives. Both types of reactions were scaled up to 1 g, and the organocatalysts were recovered by extractive workup and reused without any appreciable loss in activity. DFT calculations support the stereochemical results of the intermolecular process and the bifunctional role played by the organocatalyst by providing a computational comparison of the H-bonding networks occurring with catalysts 2a and 2b.

Synthesis of Chromen[4,3-b]pyrrolidines by Intramolecular 1,3-Dipolar Cycloadditions of Azomethine Ylides: An Experimental and Computational Assessment of the Origin of Stereocontrol

Azomethine ylides, generated from imine-derived O-cinnamyl or O-crotonyl salicylaldeyde and α-amino acids, undergo intramolecular 1,3-dipolar cycloaddition, leading to chromene[4,3-b]pyrrolidines. Two reaction conditions are used: (a) microwave-assisted heating (200 W, 185 °C) of a neat mixture of reagents, and (b) conventional heating (170 °C) in PEG-400 as solvent. In both cases, a mixture of two epimers at the α-position of the nitrogen atom in the pyrrolidine nucleus was formed through the less energetic endo-approach (B/C ring fusion). In many cases, the formation of the stereoisomer bearing a trans-arrangement into the B/C ring fusion was observed in high proportions. Comprehensive computational and kinetic simulation studies are detailed. An analysis of the stability of transient 1,3-dipoles, followed by an assessment of the intramolecular pathways and kinetics are also reported.

Solvent-Induced Reversal of Enantioselectivity in the Synthesis of Succinimides by the Addition of Aldehydes to Maleimides Catalysed by Carbamate-Monoprotected 1,2-Diamines

A simple change in the polarity of the solvent allows both enantiomers of substituted succinimides to be obtained in the enantioselective conjugate addition reaction of aldehydes, mainly α,α-disubstituted, to maleimides catalysed by chiral carbamate-monoprotected trans-cyclohexane-1,2-diamines. Using a single enantiomer of the organocatalyst, both enantiomers of the resulting Michael adducts are obtained in high yields by simply changing the reaction solvent from aqueous DMF (up to 84 % ee) to chloroform (up to 86 % ee). Theoretical calculations are used to explain this uncommon reversal of the enantioselectivity; two transition state orientations of different polarities are differently favoured in polar or nonpolar solvents.

Intención de emprendimiento y liderazgo en Colombia

La relación entre el liderazgo y emprendimiento es un tema de estudio y análisis relativamente nuevo. El término de liderazgo ha sido estudiado y enfocado a otras áreas de estudio, pero en cuanto a la relación existente con emprendimiento se presentan aún carencias conceptuales. A lo largo del presente estudio, se hace una revisión de la literatura la cual permite identificar y analizar estos conceptos y su relación en la última década en Colombia, consultando literatura comprendida en bases de datos en línea tales como, Redalyc, Scielo y Dialnet. En este documento, se destacan los atributos de un emprendedor y de un líder, igualmente se recogen los modelos de emprendimiento, las teorías de liderazgo, y los elementos que caracterizan cada concepto. Finalmente, se evidencia una dicotomía entre el líder y el emprendedor y se concluye que el liderazgo es una característica intrínseca del emprendimiento; sin embargo, el liderazgo no es por regla utilizado para emprender.

RICORDACI: Research on the Conservation, Restoration and Diagnosis of Cinematographic Films

This thesis is the result of the RICORDACI project, a three-year European-funded initiative involving the collaboration between the University of Bologna and the restoration laboratory of the Cineteca di Bologna, L'immagine Ritrovata, which aimed to develop innovative solutions and technologies for the preservation of cinematographic film heritage. In particular, this thesis presents new analytical methodologies to exploit two types of portable miniaturized Near Infrared spectrometers working in Diffuse Reflectance over the Short Wave Infrared (SWIR) range, to study the near infrared (NIR) spectral behavior of film base materials for an accurate, non-invasive and fast characterization of the polymer type; and for films with cellulose acetate supports, they can be employed as a diagnostic tool for monitoring the Degree of substitution (DS) affected by the loss of acetyl groups. The proposed methods offer non-invasive, fast, inexpensive and simple alternatives for the characterization and diagnosis of film bases to help the strategic planning and decision-making regarding storage, digitalization and intervention of film collections. Secondly, the thesis includes the evaluation of new green cleaning systems and solvents for the effective, fast and innocuous removal of undesired substances from degraded cinematographic films bases; these tests compared the efficiency of traditional systems and solvents against the new proposals. Firstly, the use of Deep Eutectic Solvent formulations for removing softened gelatin residues from cellulose nitrate bases; and secondly, the employment of green volatile solvents with different application methods, including the use of new electrospun nylon mats, for avoiding the dangerous use of friction for the removal of Triphenyl Phosphate blooms from the surface of cellulose acetate bases. The results obtained will help improving the efficiency of the interventions needed before the digitalization of historical cinematographic films and will pave the way for further investigation on the use of green solvents for cleaning polymeric heritage objects.

Corrientes de fondos privados europeos hacia América Latina: hechos y planteamientos

Incluye Bibliografía

Corrientes de fondos privados europeos hacia América Latina: hechos y planteamientos

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Fondos estructurales y de inversión europeos 2014-2020. Oportunidades para la discapacidad. Guía práctica

El objetivo de esta guía es aportar información clave sobre los fondos estructurales y de inversión europeos (FEIE) en el periodo 2014-2020, como herramienta fundamental de la cohesión territorial europea e instrumento para la inclusión social activa de las personas con discapacidad en España y Europa. A lo largo de la publicación, se proporciona información básica para conocer el funcionamiento de estos fondos, especialmente el Fondo Social Europeo (FSE) y el Fondo Europeo de Desarrollo Regional (FEDER), así como su programación y materialización en inversiones y actuaciones en el territorio. La información incluida en esta guía pretende brindar claves que sean de utilidad para las organizaciones representativas del movimiento de la discapacidad para ejercer su función de incidencia política a la hora de garantizar el cumplimiento de lo establecido en materia de accesibilidad universal e igualdad de oportunidades y no discriminación en la programación y ejecución de los fondos. Asimismo, busca familiarizar a las entidades del movimiento de la discapacidad distribuidas por el territorio español con el tipo de actuaciones que pueden ser cofinanciadas por los FEIE, fundamentalmente el Fondos Social Europeo, pero también de FEDER y FEADER.

Guía práctica de gestión de proyectos europeos.

Resumen tomado de la publicación

Guia pràctica de gestió de projectes europeus. 'Guía práctica de gestión de proyectos europeos'.

Resumen tomado de la publicación