Publications > Maôas et al

Chem. Commun. 2011, 47, 7374

A V-shaped cationic dye for nonlinear optical bioimaging.

E. Maôas^1, 2, G. Marcelo, S. Pinto, T. Cañeque, A.M. Cuadro, J.J. Vaquero, J.M.G. Martinho

1. Centro de Química-Física Molecular (CQFM), Institute of Nanoscience and Nanotechnology (IN), Instituto Superior Técnico, 1049-001 Lisboa, Portugal.  2. Departamento de Química Orgánica, Universidad de Alcalá, 28871-Alcalá de Henares, Madrid, Spain.

Resumen

A symmetric cationic molecule with D-π-A+-π-D architecture was synthesized with high two-photon absorption cross-section (σ2 ≈ 1140 GM). Application as a marker in fluorescence microscopy of living cells revealed its presence inside the cell staining vesicular shape organelles in the cytoplasm. Fluorescence lifetime imaging microscopy shows that it is also able to penetrate within the nucleus. © 2011 The Royal Society of Chemistry.

Publications > Castillo et al

Eur. J. Org. Chem. 2011, 619

Radical Intramolecular Arylation of Pyridinium Salts: A Straightforward Entry to 7-Hydroxypyrido[2,1‐a]isoquinolinylium Salts

Rafael R. Castillo, Carolina Burgos, Juan J. Vaquero, Julio Alvarez-Builla

Palabras clave: Radical reactions; Nitrogen heterocycles; Intramolecular arylation

Resumen

The synthesis of 7-hydroxypyrido[2,1‐a]isoquinolinylium salts can be achieved in moderate yields by intramolecular radical arylation of pyridinium salts obtained from substituted pyridines and o-bromophenacyl bromides.

Publications > Mantecón et al

Arkivoc 2011, 3, 42

Ethyl 4,4-dimethyl pyroglutamate (DMPG): A chiral auxiliary in cyclopropanation and carbonyl group activator.

S. Mantecón^1, 2, J.J. Vaquero, P.G. Losada, M.L. De La Puente, J.F. Espinosa, A. Rivera-Sagredo, J. Ezquerra

1. Departamento de Química Orgánica, Universidad de Alcalá, Campus Universitario, 28871-Alcalá de Henares, Madrid, Spain.  2. Centro de Investigación Lilly, Avda. de la Industria, 30, 28108-Alcobendas, Madrid, Spain.

Resumen

Reaction of ethyl (S)-N-trans-2-butenoyl-4,4-dimethyl pyroglutamate with ethyl (dimethylsulfuranylidene) acetate (EDSA) or with Trost's ylide gave rise to stereoselective cyclopropanation, promoted by the chiral auxiliary (S)-ethyl 4,4-dimethyl pyroglutamate (DMPG), which can easily be removed from the highly functionalised cyclopropanated products using various nucleophiles. © ARKAT USA, Inc.

Publications > Ramirez et al

Arkivoc 2011, 3, 140

Novel linear and V-shaped D-π-A+-π-D chromophores by Sonogashira reaction.

M.A. Ramirez^1, 2, 3, T. Cañeque, A.M. Cuadro, F. Mendicuti, K. Clays, I. Asselbergh, J.J. Vaquero

1. Departamento de Química Orgánica, Universidad de Alcalá, 28871-Alcalá de Henares, Madrid, Spain.  2. Departamento de Química Física, Universidad de Alcalá, 28871-Alcalá de Henares, Madrid, Spain.  3. Department of Chemistry, University of Leuven, Celestijnenlaan 200 D, B-3001, Belgium.

Resumen

Dipolar V-shaped chromophores derived from the pyridinium cation as the acceptor have been synthesized by Sonogashira reaction and their linear and nonlinear optical properties have been studied and compared to those of analogous one-dimensional derivatives. ©ARKAT USA, Inc.

Publications > Deligeorgiev et al

Monatsh. Chem. 2011, 142, 895

An environmentally benign procedure for the synthesis of substituted 2-thiobenzothiazoles, 2-thiobenzoxazoles, 2-thiobenzimidazoles, and 1,3-oxazolopyridine-2-thiols.

Todor G. Deligeorgiev, Stefka S. Kaloyanova, Nedyalko Y. Lesev, Juan J. Vaquero

Resumen

An improved environmentally benign procedure for the synthesis of substituted 2-thio-benzothia(oxa)zoles, 2-thiobenzimidazoles, and 1,3-oxazolopyridine-2-thiols by cyclization of 2-aminophenols, 2-aminothiophenols, 1,2-phenylenediamines, or 2-amino-3-hydroxypyridines with potassium O-ethyldithiocarbonate in PEG 400 or glycerol under directed microwave irradiation is described. The method can be applied to the synthesis of a variety of derivatives.

Publications > Vasilev et al

Coloration Technology. 2011, 127, 69

Synthesis of novel tetracationic asymmetric monomeric monomethine cyanine dyes – highly fluorescent dsDNA probes

Aleksey Vasilev, Todor Deligeorgiev, Stefka Kaloyanova, Stanimir Stoyanov, Vera Maximova, Juan J Vaquero, Julio Alvarez-Builla

Resumen

Quaternisation of monomethine cyanine dyes bearing haloalkyl chains, with the appropriate monoquaternised 1,4-diazabicyclo%@5B2.2.2%@5Doctane derivatives, yielded novel tetracationic asymmetric monomeric monomethine cyanine dyes belonging to the thiazole orange family. The optimal conditions for this reaction were investigated. The longest wavelength absorption maxima of the studied dyes are in the region 504?507?nm. The molar absorptivities of the target dyes are high, with values between 70?500 and 99?500?l?mol?1?cm?1. The fluorescence intensity and the fluorescence quantum yields of the free dyes in solution or in the presence of double-stranded DNA were determined using thiazole orange for comparison. The dyes are suitable for nucleic acid detection and have a high binding affinity, attributable to their four positive charges.

Publications > Hernando et al

Critical Reviews in Environmental Science and Technology 2011, 41, 699

Environmental Risk Assessment of Emerging Pollutants in Water: Approaches Under Horizontal and Vertical EU Legislation

M. D. Hernando, A. Rodríguez, J. J. Vaquero, A. R. Fernández-Alba, E. García

Resumen

In Europe, under the framework of environmental legislation, various protocols have been developed for assessing the environmental risk of chemicals. For the ?new chemicals,? environmental risk assessment (ERA) was introduced at 1980s. A decade later, pharmaceuticals were considered in the discussion for further ERA studies. Pesticides and biocides undergo a rigorous assessment following Directives 91/414/EEC and 98/8/EC. Registration, Evaluation, Authorisation of Chemicals (REACH) is the most important development in this field. REACH covers nanotechnology-based materials, but present methodologies may not be appropriate. The authors give a critical overview of the approaches under European water legislation, which cover the ERA frameworks for emerging contaminants.

Publications > Nuñez et al

Eur. J. Org. Chem. 2011, 1280

Ring-Closing Metathesis Approach to Heteroaromatic Cations: Synthesis of Benzo[a]Dquinolizinium Salts

Ana Nuñez, Beatriz Abarca, Ana M. Cuadro, Julio Alvarez-Builla, Juan J. Vaquero

Palabras clave: Synthetic methods; Nitrogen heterocycles; Metathesis; Benzo[a]Dquinol­izinium salts

Resumen

Benzo[a]Dquinolizinium salts have been synthesized through ring-closing metathesis reactions of 1-butenyl-2-vinylisoquinolinium, 2-butenyl-1-vinylisoquinolinium and 2-styryl-1-vinylpyridinium salts in the presence of Grubbs and Hoveyda?Grubbs catalysts. The results show that the lastapproach is the most efficient for the preparation of this heteroaromatic tricyclic system and several previously unknown derivatives have been prepared.