Publications 2010

2010

Microwave-Assisted Stille Reactions as a Powerful Tool for Building Polyheteroaryl Systems Bearing a (1H)-1,2,4-Triazole Moiety

C Cebrián, Ad Cózar, P Prieto, A Díaz-Ortiz, Adl Hoz, JR Carrillo, AM Rodriguez, F Montilla.

Stille couplings and the combination of Stille/Heck cross-coupling reactions provide useful access to tricyclic systems with valuable mate rial properties from 3,5-dibromo-1,2,4-triazoles. The reactions can all be dramatically improved under microwave irradiation – Synlett (2010) pp. 55-60

Computational calculations in microwave-assisted organic synthesis (MAOS). Application to cycloaddition reactions

A De Cózar, M. C Millán, C Cebrián, P Prieto, A Díaz-Ortiz, A De La Hoz, F. P Cossío.

Computational calculations represent a very useful tool to study separately the occurrence of thermal and non-thermal effects of microwave irradiation through the determination of the thermodynamic and kinetic parameters of the reaction. In this paper, we approach the computational study of two previously reported cycloaddition reactions. All of the outcomes indicate the presence of a thermal effect alone for the microwave irradiation that produces changes in the regioselectivity or in the reaction mechanism. – Org. Biomol. Chem. (2010) vol. 8 (1000) pp. 1009

On-line monitoring of a microwave-assisted chemical reaction by nanoliter NMR-spectroscopy

M Gomez, Hein Verputten, Angel Diaz-Ortiz, Andres Moreno, Antonio de la Hoz, Aldrik Velders. The authors report the use of a nanoliter NMR spectroscopy microfluidic chip hyphenated to a continuous-flow microliter-microwave irradn. set-up, for online monitoring and rapid optimization of reaction conditions. – Chem. Commun.  (2010) vol. 46 (25) pp. 4514-4516

Microwave-assisted synthesis of pyrazolyl bistriazines

Monica Moral, Amparo Ruiz, Andres Moreno, Angel Diaz-Ortiz, Isabel Lopez-Solera, Antonio de la Hoz, Ana Sanchez-Migallon. Reaction of 6-chloro-N,N’-bispyrazolyl-[1,3,5]triazine-2,4-diamines with 4-aminobenzylamine under microwave irradn. produces bistriazines in excellent yields.  The use of a diamine bearing amino groups with different reactivities allowed the reaction to be carried out in two steps and selectively gave monotriazines, bistriazines with identical substituents and differently substituted bistriazines.  The structures of these new compds. have been studied by NMR spectroscopy, mass spectrometry and in one case by X-ray crystallogrphy.  These new bistriazines have promising applications in supramol. chem. based on hydrogen bonds and/or complexation with metals.  The presence of a rigid linker can be used for the efficient prepn. of extended supramol. polymers with interesting fluorescence properties by complexation with cyanuric and barbituric acid derivs. – Tetrahedron (2010) vol. 66 (1) pp. 121-127

Gold Dendrimer Encapsulated Nanoparticles as Labeling Agents for Multiwalled Carbon Nanotubes

M Herrero, Javier Guerra, V Myers, M Gómez, Richard Crooks, Maurizio Prato.

In this paper, we report the functionalization of the surface of multiwalled carbon nanotubes (MWNTs) with Au dendrimer encapsulated nanoparticles (DENs). The results show that, when pristine MWNTs having hydrophobic surfaces are exposed to DENs, the dendrimers aggregate on the MWNT surface. However, when the MWNTs are oxidized in acid prior to exposure to DENs, well-dispersed submonolayer coverages of Au nanoparticles are observed on the MWNT surface. This suggests that acid-induced debundling of the nanotubes is an essential prerequisite for attachment of nearly monodisperse DENs. Electron microscopy and NMR spectroscopy confirm that the structures of the DENs and dendrimers are retained after immobilization on the surface of acid-functionalized MWNTs. – ACS Nano (2010) vol. 4 (2) pp. 905-912

Versatile microwave-induced reactions for the multiple functionalization of carbon nanotubes

Noelia Rubio, M Herrero, Antonio de la Hoz, Moreno Meneghetti, Maurizio Prato, Ester Vazquez. Carbon nanotubes (CNTs) have been readily functionalized by microwave activation using two different reactions affording functional derivs. characterized by two orthogonally protected amino groups.  The doubly functionalized CNTs can serve as multipurpose, versatile synthons in materials science and biol. applications. – Org. Biomol. Chem. (2010) vol. 8 (8) pp. 1936-1942

Synthesis and Characterization of a Carbon Nanotube−Dendron Series for Efficient siRNA Delivery

M Herrero, Francesca Toma, Khuloud Al-Jamal, Kostas Kostarelos, Alberto Bianco, Tatiana Da Ros, Fouzia Bano, Loredana Casalis, Giacinto Scoles, Maurizio Prato.

Corrections – J. Am. Chem. Soc. (2010) vol. 132 (5) pp. 1731-1731

Hybrid materials based on Pd nanoparticles on carbon nanostructures for environmentally benign C-C coupling chemistry

Javier Guerra, Maria Herrero. The combination of different nanomaterials such as metallic nanoparticles and carbon nanostructures in a new hybrid material should give rise to interesting properties that combine the advantages of each of the nanocomponents. This review highlights the latest advances in the synthetic design of these hybrid materials where carbon nanostructures act as supports as well as stabilizing agents for very reactive metallic nanoparticles. The striking applications of Pd nanoparticles anchored on the surface of carbon nanostructures in C–C coupling chemistry are analyzed. Special emphasis is placed on the stability of these materials, which is linked to their recyclability. Numerous examples are given that involve the use of these catalysts in Heck, Suzuki and Sonogashira coupling reactions. – Nanoscale (2010) vol. 2 (8) pp. 1390-1400

Synthesis and Spectroscopic Properties of Porphyrin Derivatives of C60

M Prato C Soombara E Vazquez J Niziol E Gondekc I Raud F Kajzarde. Chemical synthesis of two C60 fullerene derivatives: with porphyrin (C60-H2P) and of the iodide salt of Zn porphyrin (C60-ZnP)+I- is described. Both compounds are soluble in several organic solvents, with a larger solubility observed for C60-H2P. Thin films obtained by solution drawing or by spinning techniques from C60-H2P solution in organic solvents or dissolved in a polymer matrix show a peculiar granular structure with regular submicron size particles. Their size of is a little smaller in polymer matrix. The solution UV-Vis absorption spectra exhibit typical bands which can be attributed to porphyrin and to the fullerene. A solvatochromic effect is observed in C60-H2P which shows a nonzero first hyperpolarizability β, most likely due to the charge transfer between fullerene and porphyrin. – Mol. Crys. Liq. Crys. (2010) vol. 521 pp. 253-264

Functionalization of carbon nanotubes for applications in materials science and nanomedicine

Ester Vázquez, Maurizio Prato. Carbon nanotubes (CNTs) can be functionalized using a variety of efficient protocols. Especially, esterification and amidation reactions are exploited along with 1,3-dipolar cycloadditions. The use of microwaves (MWs) to activate the reactivity of CNTs is also reported. Innovative NMR methodologies can be introduced to investigate the covalent attachment of organic moieties to CNTs. – Pure Appl. Chem. (2010) vol. 82 (4) pp. 853-861

Photoluminescence and Electro-Optic Kerr Effect in Porphyrin Derivatives of C60

J Niziol, M Prato, C Soombar, E Vazquez, E Gondek, I Rau, F Kajzar. Photoluminescence and electro-optical properties of two C60 fullerene derivatives: with porphyrin (C60) and of an iodide salt of Zn porphyrin (C60-ZnP) are reported. Both studies were done in solution. In the case of the (C60) the photoluminescence spectra depend strongly on the solvent used and emission from B band is quenched in dioxane. For the idodide salt [C60-ZnP] both emissions from B and Q bands are observed. In all studied cases the photoluminescence at 650 nm is present, however it is excited in the iodide salt only for certain excitation energies. The EO Kerr effect measurements show a very slow rotation of molecules under the applied electric field. This rotation is more complex in the case of the iodide salt. – Molecular Crystals and Liquid Crystals (2010) vol. 522 pp. 191-202

Enhanced cellular internalization and gene silencing with a series of cationic dendron-multiwalled carbon nanotube:siRNA complexes

K. T Al-Jamal, F. M Toma, A Yilmazer, H Ali-Boucetta, A Nunes, M.-A Herrero, B Tian, A Eddaoui, W. T Al-Jamal, A Bianco, M Prato, K Kostarelo.

One of the major obstacles to the clinical development of gene silencing by small interfering RNA (siRNA) is its effective cytoplasmic delivery. Carbon nanotubes have been proposed as novel nanomaterials that can offer significant advantages for the intracellular delivery of nucleic acids, such as siRNA. We recently demonstrated in a proof-of-principle study that amino-functionalized multiwalled carbon nanotubes (f-MWNT) can effectively deliver in vivo an siRNA sequence, triggering cell apoptosis that results in human lung xenograft eradication and prolonged survival. In the present study, we demonstrate how a newly synthesized series of polycationic dendron-MWNT constructs with a precisely tailored number of amino functions (dendron generations) can complex and effectively deliver double-stranded siRNA to achieve gene silencing in vitro. A systematic comparison between the f-MWNT series in terms of cellular uptake, cytotoxicity, and siRNA complexation is offered. Significant improvement in siRNA delivery with the dendron-MWNT conjugates is shown, and gene silencing was obtained in 2 human cell lines using 2 different siRNA sequences. The study reveals that through f-MWNT structure-biological function analysis novel nanotube-based siRNA transfer vectors can be designed with minimal cytotoxicity and effective delivery and gene-silencing capabilities.—Al-Jamal, K. T., Toma, F. M., Yilmazer, A., Ali-Boucetta, H., Nunes, A., Herrero, M.-A., Tian, B., Eddaoui, A., Al-Jamal, W. T., Bianco, A., Prato, M., Kostarelos, K. Enhanced cellular internalization and gene silencing with a series of cationic dendron-multiwalled carbon nanotube:siRNA complexes. – The FASEB Journal (2010) vol. 24 (11) pp. 4354-4365

Synergy between microwave irradiation and heterogeneous catalysis in an environmentally friendly self-condensation of hydroxybenzene derivatives

M Gomez, Andres Moreno, Ester Vazquez, Antonio de la Hoz, Ana Aranda, Angel Diaz-Ortiz. Self-condensation of 1,3,5-trihydroxybenzene and 3,5-dimethoxyphenol using solid acid catalysts and microwave irradn. produces polyhydroxy-substituted biphenyls I (R = OH, MeO) in moderate to good yields.  Condensation of 1,3,5-trihydroxybenzene with p-benzoquinone gives 2,2′-dihydroxybiphenyls, e.g. II, in good yields.  These reactions do not occur or afford only traces of the desired products when classical heating is used. [on SciFinder(R)] – ARKIVOC (Gainesville, FL, U. S.) (2010) (3) pp. 264-273

Straightforward Generation of Helical Chirality Driven by a Versatile Heteroscorpionate Ligand: Self-Assembly of a Metal Helicate by Using CH-π Interactions

Antonio Otero, Agustín Lara-Sánchez, Juan Fernández-Baeza, Carlos Alonso-Moreno, Juan Tejeda, José A Castro-Osma, Isabel Márquez-Segovia, Luis F Sánchez-Barba, Ana M Rodríguez, M. Victoria Gómez. The synthesis of novel architectures, through the use of versatile heteroscorpionate ligands, was developed that allows helical chirality in aluminium complexes. – Chem. Eur. J. (2010) vol. 16 (29) pp. 8615-8619

 

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