Browsing by browse.metadata.contributordepartment "Química Orgánica"
Now showing 1 - 20 of 31
Results Per Page
Sort Options
- PublicationEmbargo1,2-Insertion reactions of alkynes into Ge–C bonds of arylbromogermylene(Royal Society of Chemistry, 2020-05-05) Sugahara, Tomohiro; Espinosa Ferao, Arturo; Rey Planells, Alicia; Guo, Jing-Dong; Aoyama, Shin; Igawa, Kazunobu; Tomooka, Katsuhiko; Sasamori, Takahiro; Hashizume, Daisuke; Nagase, Shigeru; Tokitoh, Norihiro; Química Orgánica1,2-Insertion reactions of alkynes into the Ge–C bonds in dibromodigermenes afford stable crystalline bromovinylgermylenes. In contrast to previously reported Lewis-base-supported vinylgermylenes, the bromovinylgermylene obtained from reaction of the bromogermylene with 3-hexyne via such an 1,2-insertion is a donor-free monomer. A feasible reaction mechanism, proposed on the basis of the observed experimental results in combination with theoretical calculations, suggests that the [1+2]-cycloadduct and the insertion product are the kinetic and thermodynamic product, respectively.
- PublicationEmbargo1,4-Dioxepanes, 1,4-Oxathiepanes, and 1,4-Dithiepanes(Elsevier, 2022) Sanchez-Andrada, Pilar; Lopez-Leonardo, Carmen; Alajarin, Mateo; Química OrgánicaThe focus of this article has been the progress on aromatic systems containing two of the heteroatoms O or S in 1,4-relative positions. Firstly, the reactivity of 1,4-dioxepanes, 1,4-oxathiepanes and 1,4-dithiepanes are collected and then, the syntheses of these heterocycles are summarized. Prominent synthetic methods have often been driven by a desire to prepare new materials and compounds with biological activities.
- PublicationOpen AccessAccess to ligand-stabilized PH-containing phosphenium complexes(Royal Society of Chemistry, 2024-01-04) Biskup, David; Schnakenburg, Gregor; Espinosa Ferao, Arturo Francisco; Streubel, Rainer; Química OrgánicaWhile the chemistry of phosphenium compounds, including metal complexes thereof, is very well established, few derivatives having a P–H bond have been described, yet. This work describes rational access to donor-stabilised phosphenium metal complexes possessing a P–H bond using protonation reactions of stable phosphinidene complex adducts. While most Brønsted–Lowry acids yield formal 1,1-addition products at the phosphorus centre under the loss of the donor, super-strong acids having weakly coordinating anions enable access to donor-stabilised P–H hosphenium complex salts. The latter possess N-methylimidazole as a donor (to phosphorus) and the N–P interaction has been studied theoretically.
PublicationRestrictedAccessing polysubstituted oxazolidines, pyrrolidines and imidazolidines by regioselective [3+2] annulations of ketenimines with donor-acceptor oxiranes and aziridines(Royal Society of Chemistry, 2018-05-09) Alajarín, Mateo; Banon, David; Egea, Adrian; Marin-Luna, Marta; Orenes, Raul A.; Vidal, Angel; Química OrgánicaEfficient [3 + 2] annulations of N-aryl-C,C-diphenyl ketenimines with metallo-carbonyl and metallo-azomethine ylides, generated via the respective Yb(OTf)3 and Y(OTf)3 promoted carbon–carbon bond heterolysis of donor–acceptor oxiranes and aziridines, have been accomplished. These reactions proceeded under mild conditions and supplied a general methodology for the regioselective construction of structurally complex oxazolidines and pyrrolidines. Moreover, heating neat mixtures of N-aryl-C,C-diphenyl ketenimines and diethyl aziridine-2,3-dicarboxylates led to imidazolidine derivatives. A computational study concluded in stepwise mechanisms for these [3 + 2] annulations, also shedding light on their regioselectivity, concerning which of the two cumulated double bonds of the ketenimine becomes involved in the reaction with the ylide.- PublicationEmbargoAccurate ring strain energy calculations on saturated three-membered heterocycles with one group 13–16 element(American Chemical Society, 2020-08-17) Rey Planells, Alicia; Espinosa Ferao, Arturo; Química OrgánicaAccurate ring strain energy (RSE) data for parent (CH2)2X rings are reported, where X are group 13–16 elements (El) in their lowest oxidation state, from the second to the sixth row, with their covalence completed by bonds to H. They are obtained from appropriate homodesmotic and hyper-homodesmotic reactions at different levels up to the CCSD(T) level, thus providing a benchmark of high-quality reference RSE values, as well as acceptably accurate faster lower-level options. Derivatives of indium, thallium, and lead cannot be properly described by a three-member ring connectivity, because they display a unique donor–acceptor structure from an ethylene π(C═C) orbital to an empty p orbital of a metallylene subunit. The RSE of groups 13 and 14 heterocycles increases on descending in the group (except for Ga and Ge), while it decreases for groups 15 and 16. The latter is presumably due to a strain-releasing mechanism favored by the increase of p-character at the sp3-type atomic orbital used by El in the endocyclic El–C bonds, %p(El)El-C, originated by the tendency of the El lone pairs in groups 15–16 to increase their s-character. This strain-releasing mechanism does not exist in heavier tetrels, which keep almost unchanged the p-character in the endocyclic bonds at El, whereas for triels the p-character is still lower owing to their sp2-like hybridization. Remarkable linear correlations were found between the RSE and either the above-mentioned %p(El)El-C, the distal C–C bond distance or the relaxed force constants for the endocyclic bond angles.
- PublicationOpen AccessCDK9: a key player in cancer and other diseases(Wiley, 2017-07-19) Franco, Lia Carolina; Morales, Fátima; Boffo, Silvia; Giordano, Antonio; Química OrgánicaCyclin-Dependent Kinase 9 (CDK9) is part of a functional diverse group of enzymes responsible for cell cycle control and progression. It associates mainly with Cyclin T1 and forms the Positive Transcription Elongation Factor b (p-TEFb) complex responsible for regulation of transcription elongation and mRNA maturation. Recent studies have highlighted the importance of CDK9 in many relevant pathologic processes, like cancer, cardiovascular diseases, and viral replication. Herein we provide an overview of the different pathways in which CDK9 is directly and indirectly involved.
- PublicationOpen AccessConformational analysis of 2,5-diaryl-4-methyl-2,4-dihydro-3H-1,2,4-triazol-3-ones: Multinuclear NMR and DFT calculations(Wiley, 2021-02-13) Sánchez Andrada, Pilar; Marín Luna, Marta; Alkorta, Ibon; Elguero, José; Percho, Gema; Santa María, Dolores; Claramunt, Rosa M.; Química Orgánica; Química Orgánica y Bio-Orgánica, Facultad de Ciencias, UNED, Madrid, SpainConformational exploration of five 2,5‐diaryl‐4‐methyl‐2,4‐dihydro‐3 H ‐1,2,4‐triazol‐3‐ones has been carried out based on a combination of their NMR chemical shifts determined in CDCl 3 and the scrutiny of their computed relative energies and absolute shieldings calculated at the DFT/GIAO/B3LYP/6–311++G(d,p) level. The very flat potential energy curves corresponding to the three relevant single bond rotations were explored by calculating the energy of the rotational barriers and comparing the experimental chemical shifts with those theoretically calculated in each rotamer by statistical analysis.
- PublicationOpen AccessEffective encapsulation of C60 by metal-organic frameworks with polyamide macrocyclic linkers(WILEY-VCH VERLAG GMBH, 2021) Saura-Sanmartin, Adrian; Martinez-Cuezva, Alberto; Marín-Luna, Marta; Bautista Cerezo, Delia; Berná Cánovas, José; Química OrgánicaA flexible benzylic amide macrocycle, functionalized with two carboxylic acid groups, was employed as the organic ligand for the preparation of robust copper(II)- and zinc(II)-based metal-organic frameworks. These polymers crystallized in the C2/m space group of the monoclinic crystal system, creating non-interpenetrated channels in one direction with an extraordinary solvent-accessible volume of 46%. Unlike metal-organic rotaxane frameworks having benzylic amide macrocycles as linkers, the absence of the thread in these novel reticular materials causes a decrease of dimensionality and an improvement of pore size and dynamic guest adaptability. We studied the incorporation of fullerene C60 inside the adjustable pocket generated between two macrocycles connected to the same dinuclear clusters, occupying a remarkable 98% of the cavities inside the network. The use of these materials as hosts for the selective recognition of different fullerenes was evaluated, mainly encapsulating the smaller size fullerene derivative in several mixtures of C60 and C70.
- PublicationOpen AccessEnantiospecific synthesis of antifungal dasyscyphin E from cupressic acid(Elsevier, 2017-11-16) Fernandez, Antonio; Boulifa, Ettahir; Jimenez, Fermin; Mahdjour, Soumicha; Ahmed I., Mansour; Chahboun, Rachid; Alvarez-manzaneda, Enrique; Química OrgánicaThe first synthesis of the sesquiterpene quinol dasyscyphin E has been achieved starting from cupressic acid. Key steps of the synthetic sequence are the oxidative degradation of the diterpene side chain to give a methylketone, the diastereoselective a-methylation of a protected ketoaldehyde, the subsequent intramolecular aldol condensation and the further Diels-Alder cycloaddition of a dienol ester.
- PublicationOpen AccessEnhancing the selectivity of prolinamide organocatalysts using the mechanical bond in [2]rotaxanes(Royal Society of Chemistry, 2020-03-11) Calles, Maria; Puigcerver, Julio; Alonso, Diego A.; Alajarín, Mateo; Martinez-Cuezva, Alberto; Berná Cánovas, José; Química OrgánicaThe synthesis of a pair of switchable interlocked prolinamides and their use as organocatalysts in three different enamine-activated processes are reported. A diacylaminopyridine moiety was incorporated into the thread for directing [2]rotaxane formation further allowing the association of complementary small molecules. The rotaxane-based systems were tested as organocatalysts in asymmetric enamine-mediated processes, revealing a significantly improved catalytic ability if compared with the non-interlocked thread. The presence of an electron-withdrawing nitro group at the macrocycle helps to achieve high conversions and enantioselectivities. These systems are able to interact with N-hexylthymine as a cofactor to form supramolecular catalysts displaying a divergent catalytic behaviour. The presence or absence of the cofactor controls the chemoselectivity in competitive reactions.
- PublicationOpen AccessExploring the Conversion of Macrocyclic 2,2 '-Biaryl Bis(thioureas) into Cyclic Monothioureas: An Experimental and Computational Investigation(American Chemical Society, 2018-10-23) Alajarín, Mateo; Lopez-Leonardo, Carmen; Orenes, Raul A.; Pastor Vivero, Aurelia; Sanchez-Andrada, Pilar; Vidal, Angel; Química OrgánicaMacrocyclic bis(thioureas) derived from 2,2’-biphenyl and binaphthyl skeletons have been synthesized by reaction of 2,2’-diaminobiaryl and 2,2’-bis(isothiocyanato)biaryl derivatives. The splitting of these bis(thioureas) into two units of the respective cyclic monothioureas has been monitored by NMR, shedding some light on the factors that control these processes. Additionally, a computational study revealed up to three mechanistic paths for the conversion of the 2,2’-biphenyl-derived bis(thiourea) into the corresponding monothiourea. The proposed mechanisms account for the participation of a molecule of water as an efficient proton-switch, as well as for different classes of putative intermediates. The computational study also supports the ability of the thiourea group to participate in a plethora of processes, such as prototropic equilibria, sigmatropic shifts, heteroene and retro-heteroene reactions, and cis-trans isomerizations.
- PublicationOpen AccessHomo and heteroassembly of amide-based [2]rotaxanes using α,α′-dimethyl-p-xylylenediamines(Royal Society of Chemistry, 2019-05-16) Lopez-Leonardo, Carmen; Martinez-Cuezva, Alberto; Bautista, Delia; Alajarín, Mateo; Berná Cánovas, José; Química OrgánicaThe formation of [2] rotaxanes via a fumaramide-templated clipping reaction using alpha,alpha'-dimethyl-p-xylylenediamines is described. This process selectively affords two out of seven possible interlocked isomers due to a noticeable effect of the methyl groups on the in/ out disposition of the amide CO groups.
- PublicationOpen AccessInterlocking the Catalyst: Thread versus Rotaxane-Mediated Enantiodivergent Michael Addition of Ketones to beta-Nitrostyrene(American Chemical Society, 2019-06-19) Martinez-Cuezva, Alberto; Marin-Luna, Marta; Alonso, Diego A.; Ros-Ñiguez, Diego; Alajarín, Mateo; Berná Cánovas, José; Química OrgánicaFumaramide threads bearing one l-prolinamide fragment have been designed as templates for promoting the efficient formation of novel Leigh’s [2]rotaxanes. Both threads and rotaxanes are shown to catalyze the asymmetric addition of ketones to β-nitrostyrene in an enantio- and diastereoselective manner. Interestingly, the enantioselective course of these processes is reversed simply by changing from thread to rotaxane as catalyst. DFT computations have allowed to rationalize the stereodivergence shown by the interlocked and noninterlocked catalysts.
- PublicationOpen AccessInternal Coulombic assistance in intermolecular frustrated Lewis pair activation of dihydrogen(Royal Society of Chemistry, 2024-02-15) Rey Planells, Alicia; Espinosa Ferao, Arturo; Streubel, Rainer; Frontera, Antonio; Química Orgánica1,3-Zwitterions consisting of a phosphonium cation linked to a silicate centre through a one-atom bridge, X3P–E–SiY4 (3), are computationally studied. Their phosphonium acidic group together with a Lewis base constitute a frustrated Lewis pair (FLP) in the activation of H2, with the silicate side-arm providing Coulombic stabilization to the positive charge at the Lewis base.
- PublicationOpen AccessInternal Coulombic Assistance in Intermolecular Frustrated Lewis Pair Activation of Dihydrogen(Royal Society of Chemistry, 2024-02) Rey Planells, Alicia; Espinosa Ferao, Arturo Francisco; Streubel, Rainer; Frontera, Antonio; Química Orgánica1,3-Zwitterions consisting of a phosphonium cation linked to a silicate centre through a one-atom bridge, X3P–E–SiY4 (3), are computationally studied. Their phosphonium acidic group together with a Lewis base constitute a frustrated Lewis pair (FLP) in the activation of H2, with the silicate side-arm providing Coulombic stabilization to the positive charge at the Lewis base.
- PublicationOpen AccessLewis Acid-mediated Formation of 1,3-Disubstituted Spiro[cyclopropane-1,2'-indanes]: The Activating Effect of the Cyclopropane Walsh Orbital(American Chemistry Society, 2020-02) Alajarín, Mateo; Ballester, Francisco-Jose; Vivancos, Juan-Antonio; Orenes, Raul-Angel; Vidal, Angel; Sanchez-Andrada, Pilar; Marin-Luna, Marta; Química OrgánicaBy virtue of its alkylidenecyclopropane moiety 2-(cyclopropylidenemethyl)benzaldehyde reacts with a range of amines or thiols under Lewis acid catalysis yielding the respective 1,3-bis(arylamino) or -bis(arylthio and alkylthio)indanes spirolinked to the cyclopropane ring at carbon 2. The reaction mechanism and the peculiar contribution of the cyclopropane ring have been scrutinized by DFT calculations.
- PublicationOpen AccessMechanical bonding activation in rotaxane-based organocatalysts(Royal Society of Chemistry, 2021) Pérez Martínez, Jesús de Maria; Puigcerver, Julio; Orlando, Tainara; Martins, Marcos A. P.; Alajarín, Mateo; Martinez-Cuezva, Alberto; Berná Cánovas, José; Pastor, Aurelia; Química OrgánicaWe report here the enhanced efficiency as organocatalysts of a series of succinamide-based hydrogen-bonded [2]rotaxanes functionalized with an acyclic secondary amine as the catalytic active site. We also evaluated their catalytic activity, comparing with that of their non-interlocked threads, in an iminium-type process between crotonaldehyde and acetylacetone. The presence of an interlocked polyamide macrocycle notably increased the catalytic activity of the entwined organocatalysts. The mechanized catalysts rapidly form the reactive iminium intermediate with the aldehyde, increasing its population. The hydrogen-bonding interaction established between the macrocycle and the electrophile has been proposed as one of the reasons for the rapid formation and stabilization of this key intermediate.
- PublicationOpen AccessMechanical bonding of rigid MORFs using a tetratopic rotaxane(Royal Society of Chemistry, 2024-05-28) Saura Sanmartín, Adrián; Cutillas Font, Guillermo; Martinez-Cuezva, Alberto; Alajarín, Mateo; Esteban Betegón, Fátima; Pena Sánchez, Pilar; Gándara, Felipe; Berná Cánovas, José; Química Orgánica; Nuevas Arquitecturas en Quı´mica de Materiales, Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC)The preparation of highly rigid cobalt(II)- and copper(II)–organic frameworks incorporating a tetralactam [2]rotaxane as a ligand is described. The interlocked ligand is functionalized with two pairs of carboxylate groups placed at each counterpart, thus limiting its dynamics within the crystal. The solid structure of the metal–organic rotaxane frameworks showed different, unprecedented polycatenation modes of grids, depending on the employed metal, providing great rigidity to the structures. This rigidity has been evaluated by using single crystal X-ray diffraction analyses of the cobalt(II)–organic frameworks embedded in different solvents, observing that the lattices remain unchanged. Thus, this research demonstrates that rigid and robust materials with permanent porosity can be achieved using dynamic ligands.
- PublicationOpen AccessMechanically Planar-to-Point Chirality Transmission in [2]Rotaxanes(American Chemical Society, 2024-01-24) Puigcerver, Julio; Marin-Luna, Marta; Iglesias-Sigüenza, Javier; Alajarin, Mateo; Martinez-Cuezva, Alberto; Berna, Jose; Química OrgánicaHerein we describe an effective transmission of chirality, from mechanically planar chirality to point chirality, in hydrogen-bonded [2]rotaxanes. A highly selective mono-N-methylation of one (out of four) amide N atom at the macrocyclic counterpart of starting achiral rotaxanes generates mechanically planar chirality. Followed by chiral resolution, both enantiomers were subjected to a base-promoted intramolecular cyclization, where their interlocked threads were transformed into new lactam moieties. As a matter of fact, the mechanically planar chiral information was effectively transferred to the resulting stereocenters (covalent chirality) of the newly formed heterocycles. Upon removing the entwined macrocycle, the final lactams were obtained with high enantiopurity.
- PublicationOpen AccessMediated alkaline flow batteries: from fundamentals to application(2019-10-21) Paez, Teresa; Martinez-Cuezva, Alberto; Palma, Jesus; Ventosa, Edgar; Química OrgánicaAlkaline flow batteries are attracting increasing attention for stationary energy storage. Very promising candidates have been proposed as active species for the negative compartment, while potassium ferrocyanide (K4Fe(CN)6) has been the only choice for the positive one. The energy density of this family of batteries is limited by the low solubility of K4Fe(CN)6 in alkaline media. Herein, we propose a general strategy to increase the energy density of this family of alkaline flow batteries by storing energy in commercial Ni(OH)2 electrodes confined in the positive reservoir. In this way, K4Fe(CN)6 dissolved in the electrolyte acts not only as electroactive species but also as charge carrier between current collector and solid Ni(OH)2 particles located in an external reservoir. A storage capacities of 29 Ah L–1 for the positive compartment is demonstrated. The concept is implemented in three systems, Zn–K4Fe(CN)6, anthraquinone–K4Fe(CN)6, and phenazine–K4Fe(CN)6 alkaline flow battery, showing the versatility of the strategy. Challenges and future directions to exceed the 16 Wh Ltotal–1 demonstrated in this work are discussed.