The transmetalation step in Pd-catalyzed processes: understanding the role of the classical nucleophile, the ligands and the synthetic potential of a third metal

The transmetalation step of Pd-catalyzed reactions is studied in-depth in this Doctoral Thesis. New bimetallic systems based on the Au/Pd and the Cu/Pd couple have been developed in the context of the Stille reaction and the Hiyama reaction that are very efficient for the coupling of bulky groups. This type of couplings are very challenging with other methodologies and provide excellent results under a synthetic point of view with our bimetallic approach. The bimetallic systems have been examined under a mechanistic point of view. The role of the cocatalyst, the auxiliary ligands and the tin and silicon organometallics have been understood, providing relevant information for the improvement of these systems and the development of new others. The secondary transmetalations that lead to undesired byproducts in the Negishi reaction have been studied in detail by experimental and computational techniques. The information obtained in our study provides important information that will contribute to develop more efficient Negishi reactions. A ligand designed in our group to promote challenging reductive eliminations has been tested for the Pd-catalyzed fluorination and trifluoromethylation of aryl halides. The ligand is not effective for this reaction due to the existence of a migratory insertion process that prevents the desired reductive elimination. This process has been studied by DFT calculations. The mechanisms of the N-H activation of anilines by Ir(PCP) complexes has been carried out by experimental and computational techniques. The information obtained will be used to design more efficient reactions based on this activation.Departamento de Química Física y Química InorgánicaDoctorado en Química: Química de Síntesis, Catálisis y Materiales Avanzado

Producing more food in a sustainable way is possible : biotechnological and sustainable fertilisation as a way to face population growth

The dramatic increase in the world?s population expected in this century will force a proportional increase in agricultural production in order to ensure the food supply. However, society is now demanding new, more sustainable, and environmentally friendly production methods. In order to achieve this sustainable increase, new biotechnological tools such as gene editing or synthetic biology will have to be used, leveraging the knowledge generated by researchers over decades. The soil microbiome is emerging as a powerful biotechnological tool. The beneficial microorganisms harboured in soils promote plant growth by supplying nutrients and producing hormones and secondary metabolites. Thus, these microorganisms will likely be able to help increase agricultural production in a sustainable way

In Situ Generation of ArCu from CuF2 Makes Coupling of Bulky Aryl Silanes Feasible and Highly Efficient

Producción CientíficaA bimetallic system Pd/CuF2, catalytic in Pd and stoichiometric in Cu, is very efficient and selective for the coupling of fairly hindered aryl silanes with aryl, anisyl, phenylaldehide, or pyridyl iodides of conventional size. The reaction involves the activation of the silane by CuII followed by disproportionation and transmetalation from the CuI(aryl) to PdII, on which coupling takes place. The CuIII formed in the disproportionation is reduced to CuI(aryl) by the aryl silane in excess, so that the CuF2 used is fully converted into CuI(aryl) and used in the coupling. Moreover, no extra source of fluoride is needed. Interesting size selectivity towards coupling is found in competitive reactions of hindered aryl silanes. Easily accessible [PdCl2(IDM)(AsPh3)] is by far the best catalyst, and the isolated products are esentially free of As or Pd (< 1 ppm). The mechanistic aspects of the process are experimentally examined and discussed.Ministerio de Economía, Industria y Competitividad (CTQ2013-48406-P)Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA256U13

Enseñar a aprender: ¿ejercicios o problemas?

Tomando como ejemplo una clase de matemáticas, en este artículo se propone la solución de problemas como uno de los métodos de enseñar a aprender. Para que esta enseñanza sea efectiva tiene que partir de tareas poco rutinarias que planteen alguna dificultad a los alumnos y los obliguen a reflexionar sobre los objetivos y los procedimientos que ponen en marcha, aprendiendo a planificar, supervisar y evaluar su propio aprendizaje. Los profesores deben guiar ese aprendizaje para evitar que los estudiantes se pierda

Fibronectin in human gallbladder bile: cholesterol pronucleating and/or mucin "link" protein?

Some biliary proteins (pronucleators) seem to be essential factors for cholesterol crystal formation and crystal growth in bile. A recent study suggests that fibronectin is such a pronucleator in bile. Fibronectin also seems to closely interact with intestinal mucin. Since biliary mucin plays an important role in gallstone formation, such an interaction in bile may be of relevance in cholesterol gallstone formation. To more clearly elucidate the role of fibronectin in cholesterol gallstone disease, we measured the concentration of fibronectin in native bile of cholesterol gallstone patients and checked its influence on the cholesterol nucleation time of model bile. We further looked for a molecular interaction between biliary fibronectin and gallbladder mucin. We found that fibronectin is present in gallbladder bile of gallstone patients in low concentrations (2.6 +/- 1.2 micrograms/ml). Bile fibronectin did not interact with gallbladder mucin. Moreover, in a wide range of concentrations fibronectin had no influence on the nucleation time of model bile. We conclude that fibronectin does not seem to play a major role in cholesterol gallstone disease

MRI slice selction with scaling functions

Proceedings of: 18th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, Amsterdam, 31 Oct. - 03 Nov. 1996.A new family of amplitude-only radiofrequency modulation waveforms for slice selection in Magnetic Resonance Imaging (MRI) is presented. Based on the scaling functions associated to different wavelet families, these new envelope waves provide higher slice selectivity than gaussian or sinc functions. They are also more compact on the time domain, since no truncation is needed, allowing to reduce the time required for the slice selection process. This feature is valuable on multislice-multiecho and fast acquisitions. Their performance has been evaluated both through simulations of the Bloch equations, and by measuring the slice width of real ramp phantoms images. The simulation results show that this amplitude modulation causes a phase behaviour of the resonant protons within the selected volume that is more coherent than with other techniques. This effect can be related to the higher intensity of the images acquired with this slice selection procedure.Publicad

Intervalos de confianza en los currículums del bachillerato LOGSE

En este artículo se pretende analizar los problemas que surgen en el desarrollo de los contenidos referentes a intervalos de confianza en los distintos bachilleratos en los que están incluidos, y atacar éstos mediante la utilización de herramientas informáticas, en particular con el Matemática 3.0, incluyendo un posible notebook a partir de unas funciones programadas especialmente para hacer más fácil e intuitiva a los alumnos la compresión de los conceptos a desarrollar