Persona: Pérez Mayoral, María Elena
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Pérez Mayoral
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Publicación Developing strategies for the preparation of Co-carbon catalysts involved in the free solvent selective synthesis of aza-heterocycles(Elsevier, 2018-02) Godino Ojer, Marina; Pérez Cadenas, Agustín Francisco; Pérez Mayoral, María Elena; Martín Aranda, Rosa MaríaWe report herein different series of new zero valent Cobalt nanocarbons, as doped and supported aerogels, able to efficiently catalyze the reaction of 2-amino-5-chlorobenzaldehyde and -ketoesters, via Friedländer reaction. The reaction works under solvent-free and mild conditions affording yields over 80% in only 30 min of reaction time. The catalysts could be reused almost during two consecutive cycles without almost any activity loss. A comparative study between supported and doped-carbon aerogels, as catalysts highly efficient in the reaction, has allowed to stablish the relationship between the catalyst structure and the catalytic performance. At this regard, different parameters such as carbonization temperature and surface chemistry on the aerogels under study have been also explored. As a result, although the carbon matrix is involved in the reaction, the Co(0) nanoparticles on the carbon surface are the predominant active catalytic species. Oxygen functionalities on the oxidized samples in the surroundings of Co(0) nanoparticles probably prevent the access of the reagents, notably decreasing their catalytic performance.Publicación Porous carbons-derived from vegetal biomass in the synthesis of quinoxalines. Mechanistic insights(Elsevier, 2020-09-01) Godino Ojer, Marina; Blazquez García, R.; Matos, Ines; Bernardo, M.; Fonseca I.M.; Pérez Mayoral, María ElenaWe report herein for the first-time acid biomass-derived carbons from vegetal biomass, with high developed porosity, prepared through integrating method comprising pyrolysis and surface phosphonation, able to efficiently catalyze the synthesis of quinoxalines from 1,2-diamines and α-hydroxi ketones, under aerobic conditions. The obtained results indicate that the reaction is mainly driven by a combination of acid function strength and textural properties in terms of conversion and selectivity. Furthermore, our experimental and theoretical observations suggest that the preferred reaction pathway for this transformation, in the presence of the investigated acid carbon catalysts, involves cascade reactions including imination reaction between reactants, successive imine-enamine and keto-enol tautomerisms, heterocyclization followed by dehydration, and aromatization. While the acid sites seem to be a relevant role in each reaction step, the system formed by activated carbon and molecular oxygen could be behind the last oxidative reaction to give the corresponding nitrogen heterocycles.Publicación Basolites: A type of Metal Organic Frameworks highly efficient in the one-pot synthesis of quinoxalines from α-hydroxy ketones under aerobic conditions(Elsevier, 2020-04-01) Godino Ojer, Marina; Shamzhy, Mariya; Čejka, Jiři; Pérez Mayoral, María ElenaWe report here efficient synthesis of quinoxalines from o-phenylendiamine and α-hydroxy ketones over commercial Basolites. The concentration and type of acid centres, as CUS sites, together with the porosity of the samples strongly influence the resulting conversion and selectivity. Our results indicate that the formation of quinoxalines preferentially follows a new route, in which tautomerization reactions are also involved.Publicación Metal-free synthesis of quinolines catalyzed by carbon aerogels: Influence of the porous texture and surface chemistry(Elsevier, 2017-04-17) Godino Ojer, Marina; Soriano, Eva; Calvino Casilda, Vanesa; Maldonado-Hódar, Francisco J.; Pérez Mayoral, María ElenaWe report herein an experimental and theoretical study of the Friedländer reaction, from 2-amino-5-chlorobenzaldehyde and ethyl acetoacetate, catalyzed by free-metal nanocatalysts based on carbon aerogels, to afford quinoline 3a. The developed methodology implies the combined use of carbon aerogels with solvent-free technologies under MW irradiation yielding the corresponding quinoline with moderated yield (66%) in only 5 min of reaction time. Our results demonstrated that the reactivity of the samples upon MW irradiation is strongly dependent on the porosity and surface chemistry of the carbon aerogels, the most active catalytic species being the most acidic oxygenated functional groups, –CO2H groups originated by oxidant treatment, or even in situ by hydrolysis of –CO–O–CO–, over the carbon surface. The theoretical investigation of the reaction mechanism, by using computational methods, demonstrated that the synthesis of quinoline 3a in the absence or in the presence of carbon aerogels takes place by aldolization, subsequent heterocyclization and finally double dehydration. Relatively strong π-π stacking interactions between carbon support and reagents could be behind of the observed catalytic performance also extended for the oxygenated models. Furthermore, the concentration of –CO2H groups over the carbon surface is a key factor favoring each step of the reaction but acting as individual catalytic sites.Publicación Tantalum vs Niobium MCF nanocatalysts in the green synthesis of chromene derivatives(Elsevier, 2019-03-15) Smuszkiewicz, Agata; López Sanz, Jesús; Sobczakb, Izabela; Ziolek, María; Martín Aranda, Rosa María; Pérez Mayoral, María ElenaTaMCF silicas modified with alkaline metals can be considered a novel family of highly efficient bifunctional catalysts involved in the synthesis of chromene derivatives, from salicylaldehyde 2 and acetonitrile compounds, under mild conditions, showing enhanced catalytic performance than their NbMCF analogues. The observed reactivity was mainly attributed to the higher basicity of the Me/TaMCF but also the texture of the samples. The Me/TaMCF silicas showed higher Brønsted basicity than the Nb ones as indicated by the stronger interaction between alkali metals and Ta in the UV–vis and the test reaction experiments. On the other hand, the basicity of Me/TaMCF together the reactivity degree and steric hindrance of the starting acetonitriles are key factors influencing the reaction selectivity. In conclusion, the basicity of the samples plays an important role initiating the reaction by activation of nucleophile but also a compromise between alkaline cation size and basicity is required.Publicación Cobalt oxide-Carbon nanocatalysts with highly enhanced catalytic performance for the green synthesis of nitrogen heterocycles through Friedländer condensation(Royal Society of Chemistry, 2019-03-19) Godino Ojer, Marina; López Peinado, Antonio José; Maldonado Hódar, Francisco J.; Bailón García, Esther; Pérez Mayoral, María ElenaA novel series of eco-sustainable catalysts developed by supporting CoO nanoparticles on different carbon supports, highly efficient in the synthesis of quinolines and naphthyridines, through the Friedländer condensation, are reported for the first time. Textural properties, dispersion and location of the Co-phase are influenced by the nature of the carbon support, Co-precursor salt and metal loading, having a significant impact on the catalytic performance. Thus, the presence of the mesopores and macropores in carbon aerogels together with the homogeneous distribution of the active phase favours the formation of product 3a as a function of the metal loading. However, an increase in the metal content when using CNTs indicates the formation of CoO aggregates and an optimal concentration of 3 wt% CoO was observed, providing the highest conversion values. The carbon-based catalysts herein reported can be considered to be a sustainable alternative having advantages such as easy preparation, superior stability and notably enhanced catalytic performance, operating at lower temperature and under solvent-free conditions.Publicación Eco-friendly catalytic systems based on MgO- Supporting carbon materials for the Friedländer condensation(Wiley, 2014-12) Godino Ojer, Marina; López Peinado, Antonio José; Przepiórski, J.; Pérez Mayoral, María Elena; Soriano, E.; Martín Aranda, Rosa MaríaCarbon-supported MgO materials are excellent and sustainable catalysts for the synthesis of N-containing heterocyclic compounds by the Friedländer condensation under mild, solvent-free conditions. The results reported herein indicate that MgO is the most active catalytic species that accelerates the reaction compared with the catalytic behavior observed for the carbon material Norit RX3. On the basis of DFT calculations, a reaction mechanism that involves dual activation of the reacting structures by the catalyst is proposed. Oxide, outside: MgO supported on carbon is able to catalyze the synthesis of interesting N-containing heterocyclic compounds efficiently under mild conditions. MgO on the carbon surface is responsible for the catalytic behavior. These carbon materials are environmentally friendly catalysts for the Friedländer reaction.Publicación P-Doped carbon catalyst highly efficient for benzodiazepine synthesis. Tires valorisation(Elsevier, 2023-07-01) Godino Ojer, Marina; Ripoll Morales, Vanessa; López Peinado, Antonio José; Matos, Inés; Bernardo, María; Lapa, Nuno; Fonseca, Isabel M.; Pérez Mayoral, María ElenaCarbon catalysts prepared from pyrolysis of spent tires are found to efficiently catalyse the synthesis of benzodiazepine 1, from o-phenylendiamine 2 and acetone 3, with high conversions and selectivity, under mild reaction conditions, according to Scheme 1. The most acidic catalyst, CPN_H3PO4, obtained by chemical activation with H3PO4, resulted on the most efficient catalyst affording conversion values higher than 90 %, after 4 h of reaction time, and selectively leading to benzodiazepine 1 (90 %). On the other hand, the CPN and CPN_CO2 catalysts reached high conversions of 2 although diminished selectivity to 1, confirming that the carbon matrix is involved in the first steps of the reaction mainly catalyzing the formation of intermediate 4 as the main reaction product. Note that all the investigated catalysts are macroporous materials with pore size distribution large enough to favor diffusion of reactants and products. Therefore, the catalytic performance is mainly governed by the chemical surface, in particular by the presence of acid functions as phosphate groups anchored to the carbon surface or as SiP2O7 supported phase. Finally, considering both experimental and theoretical results, it seems that the most probable catalytic centers comprise phosphate functions in SiP2O7 catalyzing the last cyclization step to 1. Although electrophilicity of carbon acceptor (Cdouble bondN moiety) in the presence of model simulating phosphate groups anchored to the carbon surface was slightly superior, transition structure in the presence of model simulating SiP2O7 showed the smallest free energy barrier.Publicación Amino-grafted basic mesoporous silicas: a type of highly performant catalysts for the green synthesis of 2-amino-4H-chromenes(Elsevier, 2024-03-15) González Rodal, Daniel; Godino Ojer, Marina; Palomino Cabello, Carlos; Turnes Palomino, Gemma; López Peinado, Antonio José; Pérez Mayoral, María ElenaNovel series of amino-grafted mesoporous silica materials applied to the green and efficient synthesis of 2-amino-4H-chromenes, from salicylaldehydes and ethyl cyanoacetate, under mild and free-solvent conditions, is herein reported for the first time. These catalysts are easily prepared by using the post-synthetic method, by functionalizing the SBA-15 silica with the corresponding amino silanes. The observed catalytic performance is mainly controlled by the type and concentration of basic sites. The methodology herein reported could be considered as an environmentally friendly alternative for the selective chromene synthesis, which allows to achieve high yields in short reaction times using notably small amounts of the catalysts. The experimental results are also supported with theoretical calculations, which suggest that the amine groups at the silica surface are behind the observed catalytic performance with the assistance of the silica matrix.Publicación Towards selective synthesis of quinoxalines by using transition metals-doped carbon aerogels(Elsevier, 2023-11-01) Godino Ojer, Marina; Morales Torres, Sergio; Maldonado Hódar, Francisco J.; Pérez Mayoral, María ElenaTransition metal (TM)-carbon aerogels, where TM = Mo, Fe, Co or Cu, were found to be active and selective catalysts for the synthesis of quinoxalines 1, from o-phenylenediamine 2 and α-hydroxy ketones 3, becoming an efficient and sustainable alternative to other carbon-based catalysts or even MOF. Doping metal phase consisting of the corresponding metal oxides but also as zero-valent metals depending on the metal and carbonization temperature, and metal loading at the surface of carbon aerogel are key factors conditioning both reactivity and selectivity. Although metal oxides are probably the predominant active catalytic species, zero-valent metals nanoparticles (Cu0 or Co0) could be implied in the last dehydrogenation step of the reaction. Moreover, the additional functionalization with oxygenated surface groups (Co-1000PO catalyst) resulted on an enhanced reactivity probably due to the cooperation between both functions. Remarkably, Mo-500 catalyst was the most efficient sample selectively leading to the quinoxaline 1a in high conversion. Finally, our results strongly suggest different operative pathways when using TM-doped carbon aerogels depending on the metallic phase at the carbon surface. While TM-doped carbon aerogels (where TM = Fe, Co, or Cu) probably act catalyzing a sequential acid-base steps and subsequent aromatization leading to the corresponding quinoxaline 1a, Mo-doped catalyst would work via the initial oxidation of α-hydroxy ketones followed by condensation-dehydration reactions.