DigitalUM :: Browsing by browse.metadata.contributordepartment "Química Orgánica"

Browsing by browse.metadata.contributordepartment "Química Orgánica"

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1,2-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 Orgánica
1,2-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.
Open Access
1,2σ3λ3-Oxaphosphetanes and Their P-Chalcogenides ¿ A Combined Experimental and Theoretical Study
(2022-05-23) Gleim, F.; Garcia Alcaraz, A.; Schnakenburg, G.; Espinosa Ferao, A. F.; Streubel, R.; Química Orgánica
Although 1,2σ 5λ 5 -oxaphosphetanes have been known for a long time, the “low-coordinate” 1,2σ 3λ 3 -oxaphosphetanes have only been known since their first synthesis in 2018 via decomplexation. Apart from ligation of this P-heterocycle to gold(I)chloride and the oxidation using ortho-chloranil, nothing on their chemistry has been reported so far. Herein, we describe the synthesis of new 1,2σ 3λ 3 - oxaphosphetane complexes (3a–e) and free derivatives (4a–e), as well as reactions of 4a with chalcogens and/or chalcogen transfer reagents, which yielded the P-chalcogenides (14–16a; Ch = O, S, Se). We also report on the theoretical results of the reaction pathways of C-phenyl-substituted 1,2 σ 3λ 3 - oxaphosphetanes and ring strain energies of 1,2σ 4λ5 -oxaphosphetane P-chalcogenides.
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1,4-Dioxepanes, 1,4-Oxathiepanes, and 1,4-Dithiepanes
(Elsevier, 2021-11-23) Sánchez Andrada, Pilar; López Leonardo, Carmen; Alajarín Cerón, Mateo; Química Orgánica
The 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.
Open Access
2-Isocyanoanilines and their mono-Boc-protected derivatives
(Royal Society of Chemistry, 2025-07-15) Saura Sanmartín, Adrián; López Leonardo, Carmen; Alajarín Cerón, Mateo; Química Orgánica; Facultad de Química
Among the variety of synthetically useful isocyanides, 2-isocyanoanilines have been scarcely reported in the chemical literature, despite the rich chemistry that expectedly could derive from the reactivities of their two functional groups. This is the case not only for the parent compound but also for most of their N-monosubstituted derivatives. The reason behind such behavior relies upon their chemical instability, apparently attributable to the presence of the N–H bond. Among these latter species, two tert-butyl carbamates are notorious exceptions, as they have been widely utilized in multicomponent reactions but poorly described. This review covers the chemistry of these compounds from a critical perspective, analyzing the causes of the instability of these privileged molecular scaffolds, as well as highlighting the reactivity of their mono-Boc-protected derivatives.
Open Access
4-Alkenyl-2-aminothiazoles: Smart Dienes for Polar [4 + 2] Cycloadditions
(Wiley, 2012-12-06) Alajarín Cerón, Mateo; Cabrera, Jose; Sánchez Andrada, Pilar; Orenes, Raul-Angel; Pastor Vivero, Aurelia; Química Orgánica
An exhaustive investigation on the [4+2] cycloadditions of 4-alkenyl-2-aminothiazoles with a wide range of dienophiles has been carried out. 4-Alkenyl-2-aminothiazoles act as good in-out dienes reacting with dienophiles bearing electron-withdrawing groups. The heteroannulations, typically conducted under mild conditions, are endo-selective when cyclic dienophiles are employed and regioselective when the reactions are conducted with non symmetric dienophiles. The endo-selective processes presumably take place by concerted but highly asynchronous mechanisms. By contrast, the low levels of endo selectivity and the lack of stereospecificity in the reactions with certain acyclic dienophiles point to a stepwise mechanism with a zwitterion as the most plausible intermediate. The course of the reaction changes when the highly reactive PTAD and TCNE are used as dienophiles since only addition products are obtained. Calculations of the HOMO and LUMO energy values of representative 4-alkenyl-2-aminothiazoles and the results of π-facial diastereoselective processes by using chiral substrates are also disclosed.
Open Access
5-Alkenylthiazoles as In-Out Dienes in Polar [4+2] Cycloaddition Reactions
(Wiley, 2013-09-25) Alajarín, Mateo; Cabrera, Jose; Sanchez-Andrada, Pilar; Bautista, Delia; Pastor Vivero, Aurelia; Química Orgánica
5-Alkenyl-2-aminothiazoles react as in-out dienes with a wide range of electron-poor dienophiles leading to the corresponding cycloaddition products in good to excellent yields. The [4+2] cycloadditions of 5-alkenyl-2-aminothiazoles can be classified as site-selective since only the diene moiety including the formal C-C double bond of the heterocycle and that of the side-chain is involved. Calculations of the HOMO energy values of representative 5-alkenyl-2-aminothiazoles are disclosed The cycloadditions are endo-selective with N-phenylmaleimide or maleic anhydride and regioselective when the reactions are conducted with non symmetrical dienophiles. Completely oxidized cycloadducts are obtained in the reactions of 5-alkenyl-2-aminothiazoles with naphthoquinone or DMAD. Unexpectedly, the reactions with PTAD are not stereospecific. A mechanism placed at the concerted/stepwise boundary is proposed.
Open Access
A Light-Driven Interlocked Catalyst
(2018-03-06) Martinez-Cuezva, Alberto; Saura-Sanmartin, Adrian; Nicolas-Garcia, Tomas; Navarro, Cristian; Alajarín, Mateo; Berná Cánovas, José; Química Orgánica
The synthesis of mechanical interlocked molecules has received increased attention over the last decades. The mechanical bond infers particular chemical properties to these systems. Particularly the study of their chemical activity is experiencing an important growth, remarking their use as catalysts. Herein we described the synthesis and application in catalysis of a photoswitchable interlocked shuttle.
Open Access
A structural analysis of 2,5-diaryl-4H-2,4-dihydro-3H-1,2,4-triazol-3-ones: NMR in the solid-state, X-ray crystallography and GIPAW calculations
(Wiley, 2021) Marín-Luna, Marta; Sánchez-Andrada, Pilar; Alkorta, Ibon; Elguero, José; Torralba, M. Carmen; Delgado-Martínez, Patricia; Santa María, Dolores; Claramunt, Rosa M.; Química Orgánica
The 1H, 13C, 15N, and 19F nuclear magnetic resonance (NMR) spectra of 11 2,5-diaryl-2,4-dihydro-3H-1,2,4-triazol-3-ones have been acquired in DMSO-d6 solution and the 13C, 15N, and 19F NMR spectra have also been acquired in the solid state (solid-state nuclear magnetic resonance [SSNMR] and magic angle spinning [MAS]). The X-ray structures of Compounds 3, 5, and 6 have been determined by X-ray diffraction. Theoretical calculations at the gauge-independent atomic orbital (GIAO)/B3LYP/6-311++G(d,p) level have provided a set of 321 chemical shifts that were compared with 310 experimental values in DMSO-d6. To obtain good agreements, some effects need to be included. The SSNMR chemical shifts have been compared with gauge-including projector-augmented wave (GIPAW) calculations and with the heavy atom–light atom (HALA) effects.
Open Access
A Thiourea-based Rotaxane Catalyst: Nucleophilic Fluorination Phase-Transfer Process Unlocked by the Mechanical Bond
(American Chemical Society, 2025-03-18) Martínez Cuezva, Alberto; Berná Cánovas, José; Puigcerver Alarcón, Julio; Juan S. Santiago Dato; Alajarín Cerón, Mateo; Química Orgánica
We report a five-component clipping approach using activated isophthaloyl-derived esters to synthesize an amide-based thiourea rotaxane. This method overcomes acyl chloride limitations with nucleophilic thiourea threads. The steric hindrance of the mechanical bond enables, for the first time, an interlocked thiourea as a hydrogen-bonding phase-transfer organocatalyst in nu-cleophilic fluorinations. This highlights how mechanical bonds expand thiourea catalysis to processes previously incompatible with conventional catalysts.
Open Access
Access 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 Orgánica
While 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.
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Accessing 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 Orgánica
Efficient [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.
Open Access
Accurate ring strain energies of unsaturated three-membered heterocycles with one group 13–16 element
(American Chemical Society, 2022-05-02) Rey Planells, Alicia; Espinosa Ferao, Arturo; Química Orgánica
High-quality ring strain energy (RSE) data for 1H-unsaturated (CH)2X parent rings, where X is a group 13–16 element, are reported in addition to the 2H-isomers of the pnictogenirene rings. RSE data are obtained from appropriate homosdesmotic reactions and calculated at the DLPNO-CCSD(T)/def2-TZVPP//B3LYP-D3/def2-TZVP(ecp) level. 1H-Tallirene and 1H-plumbirene have unique donor–acceptor structures between an acetylene π(CC) orbital and an empty p orbital of a metallylene subunit (a Dewar–Chatt–Duncanson description) and therefore cannot be described as proper rings but as pseudocyclic structures. Also, 1H-indirene and 1H-oxirene lack ring critical points and constitute borderline cases of pseudorings. 1H-Unsaturated rings exhibit enhanced RSE compared to their saturated homologues. The mechanism of ring strain relaxation by increasing the s character in the lone pair (LP) of group 15–16 elements is remarkable and increases on descending the groups. Furthermore, RSE is affected by the aromatic character of group 13 rings and certain aromatic or antiaromatic character in group 14 or 15–16 rings, respectively, which tend to vanish on descending the group as shown by NICS(1) values. 2H-Unsaturated rings were found only for group 15 elements (although only 2H-azirine shows a proper cyclic structure) and displayed lower RSE (higher stability) than the corresponding 1H-isomers.
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Accurate 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 Orgánica
Accurate 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.
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Alkylammonium cation affinities of nitrogenated organobases: the roles of hydrogen bonding and proton transfer
(Wiley, 2021-07-12) Sánchez Andrada, Pilar; Vidal Vidal, Ángel; Prieto, Tania; Elguero, José; Alkorta, Ibon; Marin Luna, Marta; Química Orgánica
Alkylammonium cation affinities of 64 nitrogen-containing organobases, as well as the respective proton transfer processes from the alkylammonium cations to the base, have been computed in the gas phase by using DFT methods. The guanidine bases show the highest proton transfer values (191.9–233 kJ mol−1) whereas the cis-2,2’-biimidazole presents the largest affinity towards the alkylammonium cations (>200 kJ mol−1) values. The resulting data have been compared with the experimentally reported proton affinities of the studied nitrogen-containing organobases revealing that the propensity of an organobase for the proton transfer process increases linearly with its proton affinity. This work can provide a tool for designing senors for bioactive compounds containing amino groups that are protonated at physiological pH.
Open Access
Analysis of non-innocence of phosphaquinodimethane ligands when charge and aromaticity come into play
(Wiley, 2021-06-25) Junker, Philip; Rey Planells, Alicia; Espinosa Ferao, Arturo; Streubel, Rainer; Química Orgánica
Several phosphaquinodimethanes and their M(CO)5 complexes (M=Cr, Mo, W) and model derivatives have been theoretically investigated regarding the quest of non-innocence. Computed structural and electronic properties of the P-Me/NH2 substituted phosphaquinodimethanes and tungsten complexes revealed an interesting non-innocent ligand behaviour for the radical anion complexes with distonic ion character and a strong rearomatization of the middle phenyl ring. The latter was further probed taking also geometric aromaticity (HOMA) and quinoid distortion parameters (HOMQc) into account, as well as NICS(1). Furthermore, the effect of the P-substitution was investigated for real (or plausible) complexes and their free ligands focusing on the resulting aromaticity at the middle phenyl ring and vertical one-electron redox processes. The best picture of ligand engagement in redox changes was provided by representing NICS(1) values versus HOMA and the new geometric distortion parameter HOMQc8.
Open Access
Arbuzov meets 1,2-oxaphosphetanes: transient 1,2-oxaphosphetan-2-iums as entry point to beta-halo phosphane oxides and P-containing oligomers
(Royal Society of Chemistry, 2024-02-07) Gleim, Florian; Schnakenburg, Gregor; Espinosa Ferao, Arturo Francisco; Streubel, Rainer; Química Orgánica
Herein, we describe the synthesis of a 1,2r3 k3 -oxaphosphetane from ethylene oxide and its reactions with alkyl halides to form b-halo phosphane oxides in an Arbuzov-type reaction. When methyl triflate was used as a hard electrophile, cationic oligomerisation of 1,2-oxaphosphetanes was observed. DFT calculations indicate 1, 2-oxaphosphetan-2-iums as intermediates and reveal differences between the Arbuzov and the potential Perkow reaction pathway.
Open Access
Carbonylation of Boranes ¿ A Computational Study
(Royal Society of Chemistry, 2023-12-11) Espinosa Ferao, Arturo Francisco; Química Orgánica
The classical simple picture of stepwise B-to-C migratory insertion of all three alkyl groups in the carbonylation reaction of trialkyl boranes with CO was shown not to be correct, except for the first alkyl group shift affording an acyl borane. The second and third direct alkyl shifts turned out to be kinetically hampered due to the non-activated character of the B C bond in electron-poor B atoms. The latter can only be achieved by either the autocatalytic action of the final alkyl boron oxide or by formation of dimeric species with weakened B-alkyl bonds at borate centres. Both thermodynamic and several NICS-related parameters pointed to scarce, even “negative”, aromatic character for boroxines, the final cyclotrimerization products of alkyl-boron oxides
Open Access
CDK9: a key player in cancer and other diseases
(Wiley, 2017-07-19) Franco, Lia Carolina; Morales, Fátima; Boffo, Silvia; Giordano, Antonio; Química Orgánica
Cyclin-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.
Open Access
Chemodivergent Conversion of Ketenimines Bearing Cyclic Dithioacetalic Units into Isoquinoline-1-thiones or Quinolin-4-ones as a Function of the Acetalic Ring Size
(2019-06-21) Alajarín, Mateo; Marin-Luna, Marta; Sanchez-Andrada, Pilar; Vidal, Angel; Química Orgánica
C-Alkoxycarbonyl-C-phenyl-N-aryl ketenimines bearing 1,3-dithiolan-2-yl or 1,3-dithian-2-yl substituents at ortho position of the C-phenyl ring, respectively, transform into isoquino-line-1-thiones and quinolin-4-ones under thermal treatment in toluene solution. The formation of isoquinolinethiones involves a rare degradation of the 1,3-dithiolane ring, whereas, in contrast, the 1,3-dithiane ring remains intact during the reaction course leading to quinolin-4-ones. Computational density functional theory results support that the kinetically favorable mechanism for the formation of isoquinoline-l-thiones proceeds through a [1,5]-hydride shift/6 pi-electrocyclization cascade, followed by a thiirane extrusion process. Alternative mechanistic paths showing interesting electronic reorganization processes have been also scrutinized but resulted not competitive on energetic grounds.
Open Access
Co-conformational Exchange Triggered by Molecular Recognition in a Di(acylamino)pyridine-Based Molecular Shuttle Containing Two Pyridine Rings at the Macrocycle
(WILEY-VCH VERLAG GMBH, 2016-01-21) Martinez-Cuezva, Alberto; Carro-Guillen, Fernando; Pastor Vivero, Aurelia; Marin-Luna, Marta; Orenes, Raul-Angel; Alajarín, Mateo; Berná Cánovas, José; Química Orgánica
We describe the incorporation of endo-pyridine units into the tetralactam ring of di(acylamino)pyridine-based rotaxanes. This macrocycle strongly associates with the linear interlocked component as confirmed by X-ray diffraction studies of rotaxane 2b. Dynamic NMR studies of 2b in solution revealed a rotational energy barrier that was higher than that of the related rotaxane 2a, which lacks of pyridine rings in the macrocycle. The macrocycle distribution of the molecular shuttle 4b, containing two endo-pyridine rings, shows that the major co-conformer is that with the cyclic component sitting over the di(acylamino)pyridine station. DFT calculations also support the marked preference of the ring for occupying the heterocyclic binding site. The association of N-hexylthymine with the di(acylamino) pyridine binding site of 4b led to the formation of a rare 'S'-shaped co-conformer in which the tetralactam ring interacts simultaneously with both stations of the thread.

Browsing by browse.metadata.contributordepartment "Química Orgánica"

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