Covalent organocatalysis for the development of new methodologies in asymmetric synthesis

298 p.En el presente trabajo se ha aplicado la organocatálisis a la activación de sustratos versátiles como lo son los cicloporpanos funcionalizados y las inonas, para el desarrollo de nuevas metodologías sintéticas. Así, se ha empleado la química de carbenos N-heterocíclicos al desarrollo de la reacción benzoínica cruzada intermolecular entre aldehídos y cetonas, restringida a sustratos activados, mediante el empleo de inonas como electrófilos y destacando la particular eficiencia del ciclopropano carbaldehido en esta transformación.Además, se han empleado ciclopropanos dadores-aceptores en reacciones de cicloadición así como en secuencias en cascada para acceder a compuestos heterocíclicos altamente enriquecidos, tras promover su la apertura del anillo carbonado mediante carbenos N-heterocíclicos y aminas secundarias de forma alternativa, en función de los sustratos empleados

Covalent organocatalysis for the development of new methodologies in asymmetric synthesis

298 p.En el presente trabajo se ha aplicado la organocatálisis a la activación de sustratos versátiles como lo son los cicloporpanos funcionalizados y las inonas, para el desarrollo de nuevas metodologías sintéticas. Así, se ha empleado la química de carbenos N-heterocíclicos al desarrollo de la reacción benzoínica cruzada intermolecular entre aldehídos y cetonas, restringida a sustratos activados, mediante el empleo de inonas como electrófilos y destacando la particular eficiencia del ciclopropano carbaldehido en esta transformación.Además, se han empleado ciclopropanos dadores-aceptores en reacciones de cicloadición así como en secuencias en cascada para acceder a compuestos heterocíclicos altamente enriquecidos, tras promover su la apertura del anillo carbonado mediante carbenos N-heterocíclicos y aminas secundarias de forma alternativa, en función de los sustratos empleados

Analysis of the power balance In the cells of a multilevel cascaded H-Bridge converter

Multilevel cascaded H-Bridge converters (CHB) have been presented as a good solution for high power applications. In this way, several control and modulation techniques have been proposed for this power converter topology. In this paper the steady state power balance in the cells of the single phase two cell CHB is studied. The capability to be supplied with active power from the grid or to deliver active power to the grid in each cell is analyzed according to the dc-link voltages and the desired ac output voltage value. Limits of the maximum and minimum input active power for stable operation of the CHB are addressed. Simulation results are shown to validate the presented analysis

Voltage and Overpotential Prediction of Vanadium Redox Flow Batteries with Artificial Neural Networks

This article explores the novel application of a trained artificial neural network (ANN) in the prediction of vanadium redox flow battery behaviour and compares its performance with that of a two-dimensional numerical model. The aim is to evaluate the capability of two ANNs, one for predicting the cell potential and one for the overpotential under various operating conditions. The two-dimensional model, previously validated with experimental data, was used to generate data to train and test the ANNs. The results show that the first ANN precisely predicts the cell voltage under different states of charge and current density conditions in both the charge and discharge modes. The second ANN, which is responsible for the overpotential calculation, can accurately predict the overpotential across the cell domains, with the lowest confidence near high-gradient areas such as the electrode membrane and domain boundaries. Furthermore, the computational time is substantially reduced, making ANNs a suitable option for the fast understanding and optimisation of VRFBs.This work has been partially supported by the Government of the Basque Country, program: Elkartek CICe2022; Grant No.: KK-2022/00043. U.F.-G. was supported by the Mobility Lab Foundation, a governmental organization of the Provincial Council of Araba and the local council of Vitoria-Gasteiz

A Model-Based Direct Power Control for Three-Phase Power Converters

Direct Power Control (DPC) technique has been widely used as control strategy for three-phase power rectifiers due to its simplicity and good performance. The DPC uses the instantaneous active and reactive power to control the power converter, the controller design has been proposed as a direct control with a look up table (LUT), and in recent works, as an indirect control with an inner control loop with proportional plus integral controllers for the instantaneous active and reactive power errors. In this paper a model-based DPC for three-phase power converters is designed, obtaining expressions for the input control signal which allow to design an adaptive control law minimizing the errors introduced by the parameters uncertainties as the smoothing inductor value or the grid frequency. Controller design process, stability study of the system and experimental results for a synchronous three-phase power rectifier prototype are presented to validate the proposed controller

Control del Equilibrio de las Tensiones de los Condensadores Flotantes en Convertidores Multinivel de Capacidades Flotantes

SEMINARIO ANUAL DE AUTOMATICA, ELECTRONICA INDUSTRIAL E INSTRUMENTACION () (.2006.GIJON)Los convertidores de capacidades flotantes multinivel se presentan como una alternativa a otro tipo de topologías multinivel presentando ciertas ventajas. Sin embargo, presentan desventajas como el desequilibrio de tensiones de los condensadores flotantes introduciendo distorsión en las tensiones moduladas por el convertidor. Se presenta en este trabajo un algoritmo para controlar el equilibrio de estas tensiones. Este algoritmo se basa en la elección de los estados de los transistores dentro de la secuencia de conmutación usando modulación Space Vector. Este algoritmo es completamente general siendo aplicable a cualquier número de niveles e independiente de la carga. Se presentan todas las expresiones matemáticas necesarias para el control mostrándose resultados de simulación para demostrar el buen funcionamiento de la estrategia de control propuesta. Se muestran los límites de controlabilidad del algoritmo comparándolo con los límites obtenidos para otras topologías de convertidores multinivel

Computational Modeling of a 2D Vanadium Redox Flow Battery Cell

These days, the implementation of sustainable power generation has led to a difference in propensity in the energy creation and capacity frameworks, compelling them to conquer the hardships that it addresses. Considering the entirety among the suggested technologies, vanadium redox flow batteries (VRFB) stand out as a wonderful choice regarding cyclability and versatility. The point of this study is to break down electrochemical performance of a vanadium redox flow battery cell in two dimensions. To accomplish this, a two- dimensional model comprising an ion exchange membrane, electrode and flow channel was created. A set of electrode compression and flow rates was tested to envision the impact on the velocity field, species concentration and potential and current distributions. As a result of compression, velocity profiles and reaction rates are both increased, by 12.7% and 9.2%, respectively, when applying 50% compression. Higher reaction rates and more stable concentra- tion gradients were induced by higher electrolyte rates. Additionally, over- potential was reduced by 1.5% with the lowest flow rate.The authors appreciate the support to the government of the Basque Country through research program Grant N. ELKARTEK 22/85 CICe2022 KK-2022/00043. The computational support provided by the Microfluidics Cluster UPV/EHU is also gratefully acknowledged. Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature

Organocatalytically Generated Donor − Acceptor Cyclopropanes in Domino Reactions. One-Step Enantioselective Synthesis of Pyrrolo[1,2 ‑ a ]quinolines

An easy and straightforward procedure has been developed for the synthesis of highly enantioenriched pyrrolo-[1,2-a]quinolines through a one-pot process that comprises a domino cyclopropane ring opening/aza-Michael/aldol reaction followed by acid-promoted lactamization. The key feature of the synthetic approach relies on the ability of conveniently functionalized cyclopropaneacetaldehydes to undergo organocatalytic activation by a chiral secondary amine that enables the catalytic generation of a donor acceptor cyclopropane. This intermediate has the potential to undergo a ring opening that generates an electrophilic alpha,beta-unsaturated iminium ion that subsequently reacts through the already mentioned domino sequence and in which stereochemical information is very efficiently transferred from the amine catalyst to the final products. Moreover, one of the alkoxycarbonyl moieties can be easily removed by standard hydrolysis/decarboxylation, providing access to the target adducts as single stereoisomers.This research was supported by the Spanish MINECO (FEDER-CTQ2014-52107-P), the Basque Government (Grupos IT328-10), and UPV/EHU (fellowship to E.S. and UFI QOSYC 11/22). Membership in the COST action CM1407 (NatChemDrugs) is also acknowledged

Catalytic Generation of Donor-Acceptor Cyclopropanes under N-Heterocyclic Carbene Activation and their Stereoselective Reaction with Alkylideneoxindoles

Formylcyclopropanes undergo activation in the presence of an N-heterocyclic carbene catalyst generating a donor-acceptor cyclopropane intermediate with the ability to undergo ring-opening followed by formal [4+2] cycloaddition with alkylideneoxindoles. This enables the direct enantio- and diastereoselective synthesis of tetrahydropyrano[ 2,3-b]indoles through the use of a chiral NHC catalyst. Keywords: asymmetricSpanish MINECO(FEDER-CTQ2014-52107), Basque Government (Grupos IT908-16), UPV/EHU (EHUA 16/10 and UFIQOSYC11/22) for financial support. L. P. and E. S.-D