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Badajoz, Spain

Garcia de la Concepcion J.,QUOREX Research Group | Avalos M.,QUOREX Research Group | Babiano R.,QUOREX Research Group | Cintas P.,QUOREX Research Group | And 3 more authors.
Tetrahedron | Year: 2016

The spontaneous loss of sulfur or isocyanate from transient 7-thia-2-azabicyclo[2.2.1]hept-5-en-3-ones, which are initially formed by 1,3-dipolar cycloadditions of thioisomünchnones with acetylenic dipolarophiles, is the key step in the chemoselective syntheses of pyridin-2-ones or thiophenes. The way by which sulfur is released has been the subject of previous studies pointing to a concerted retro-cheletropic mechanism as a more favorable route than the alternative stepwise pathway. The latter however, is apparently prevalent for elimination of isocyanate. Working with a conformationally-restricted bicyclic thioisomünchnone that undergoes facile cycloaddition with acetylenes, sulfur elimination has now been interrogated by experiment and theoretical calculations at the M06-2X and M11 methods in combination with the 6-311++G(d,p) basis set, which unveil rather a sigmatropic shift via the intermediacy of thiirane species. These results provide new vistas and synthetic opportunities in mesoionic cycloadditions. © 2016 Elsevier Ltd Source


Romero-Fernandez M.P.,QUOREX Research Group | Avalos M.,QUOREX Research Group | Babiano R.,QUOREX Research Group | Cintas P.,QUOREX Research Group | And 3 more authors.
Organic and Biomolecular Chemistry | Year: 2014

Mono- and diaza-derivatives of malondialdehydes, namely 3-alkyl(aryl)amino-2-arylacroleins and 1,5-dialkyl(aryl)-3-arylvinamidines are open-chain systems in which extended electron delocalization and pseudoaromaticity can be envisaged. A set of diversely functionalized compounds has been synthesized and characterized by spectroscopic data and X-ray diffractometry. Quantum-chemical calculations were performed for all possible neutral tautomers and conformers in the gas phase and compared to those in polar solvents (CHCl3, DMSO, and EtOH) at the M06-2X/6-311++G(d,p) level. Tautomeric equilibria and conformational preferences can be rationalized in terms of structural factors, which can be roughly estimated as summation or subtractions of intramolecular interactions. As expected, a key role is played by intramolecular hydrogen bonds whose strength varies from the gas phase to polar ethanol. This issue also delves into the concept of resonance-assisted H-bond, where the donor and acceptor atoms are connected by a π-conjugated system. The most stable conformers (structures a and c) possess a high degree of pseudoaromaticity as inferred from HOMA indexes and other delocalization parameters. This journal is © the Partner Organisations 2014. Source


Cantillo D.,QUOREX Research Group | Avalos M.,QUOREX Research Group | Babiano R.,QUOREX Research Group | Cintas P.,QUOREX Research Group | And 3 more authors.
Journal of Organic Chemistry | Year: 2010

An intramolecular SNAr mechanism has been identified in the unexpected aryl migration observed in a mesomeric betaine. The process changes drastically the optical and spectroscopic properties and should be a valuable model for related heteroaromatic systems. © 2010 American Chemical Society. Source


Rodriguez-Cano A.,QUOREX Research Group | Rodriguez-Cano A.,CIBER ISCIII | Cintas P.,QUOREX Research Group | Fernandez-Calderon M.-C.,CIBER ISCIII | And 9 more authors.
Colloids and Surfaces B: Biointerfaces | Year: 2013

Formation of thin films on titanium alloys incorporating bioactive small molecules or macromolecules is a route to improve their biocompatibility. Aminoalkylsilanes are commonly employed as interface reagents that combine good adhesion properties with an amino tail group susceptible of further functionalization. This article introduces a reproducible methodology to obtain a cross-linked polymer-type brush structure of covalently-bonded aminoalkylsiloxane chains on Ti6Al4V. The experimental protocol can be fine-tuned to provide a high density of surface-coated amino groups (threshold value: 2.1±0.1×10-8molcm-2) as proven by chemical and spectrophotometric analyses. Using a model reaction involving the condensation of 3-aminopropyltrimethoxysilane (APTMS) on Ti6Al4V alloy, we herein show the effects of reaction temperature, reaction time and solvent humidity on the composition and structure of the film. The stability of the resulting coating under physiological-like conditions as well as the possibility of surface re-silanization has also been evaluated. To verify if detrimental effects on the biological performance of the Ti6Al4V alloy were induced by this coverage, human primary osteoblasts behavior, Staphylococci adhesion and biofilm formation have been tested and compared to the Ti6Al4V oxidized surface. Reaction with trans-cinnamaldehyde has used in order to determine useful amino groups at aminosilanized surface, XPS and UV analyses of imino derivatives generated reveal that almost a 50% of these groups are actually available at the siloxane chains. © 2013 Elsevier B.V. Source


Rodriguez-Cano A.,QUOREX Research Group | Rodriguez-Cano A.,CIBER ISCIII | Pacha-Olivenza M.-T.,CIBER ISCIII | Pacha-Olivenza M.-T.,AM UEx Research Group | And 4 more authors.
Surface and Coatings Technology | Year: 2014

The Ti6Al4V surface, commonly employed in biomedical prostheses, has been chemically functionalized by non-covalent binding to obtain improved antibacterial responses. The methodology combines the well-known antibacterial activity of silver(I) ions with those of other common antimicrobials such as carboxylic acids, trans-cinnamaldehyde, farnesol, and the broad-range antibiotic chloramphenicol. To this end, on previously aminosilanizated Ti6Al4V surfaces (Material A) were attached via saline bonds (involving both ionic and dipole interactions) acetic, propanoic, benzoic, and sorbic acids (Material B). Likewise silver(I) acetate undergoes non-covalent cross-linking with the aminosiloxane-coated surface (Material C) after incubation at 60°C for 48h, thus resulting in a density of ca. 4.11×10-8molcm-2. The coordinating ability of Ag(I) ions enables further attachment of the above-mentioned carboxylic acids onto the surface (Material D) and other neutral antimicrobials (Material E). Surface characterization has been accomplished using infrared spectroscopy and X-ray photoelectron spectroscopy, which support non-covalent binding. In particular, the existence of ammonium and carboxylate groups together with other intact functional groups (carbonyl, hydroxyl and amino) reveals that aminosiloxane-coated surfaces adhere via both ionic and weak interactions. As a proof of concept, adhesion and viability tests of Staphylococcus aureus on the functionalized surfaces show the adequate performance of the coverage at short and medium contact times with the surrounding cells. © 2014 Elsevier B.V. Source

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