Publicaciones > Mantecón et al

Arkivoc. 2011;(3), 42-53. doi: 10.3998/ark.5550190.0012.305

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.

Publicaciones > Ramirez et al

Arkivoc. 2011;(3):140-155. doi: 10.3998/ark.5550190.0012.311

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.

Publicaciones > Deligeorgiev et al

Monatsh. Chem. 2011; 142(9):895. doi: 10.1007/s00706-011-0551-1

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.

Publicaciones > Vasilev et al

Coloration Technology. 2011; 127(1):69-74. doi: 10.1111/j.1478-4408.2010.00280.x

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.

Publicaciones > Hernando et al

Critical Reviews in Environmental Science and Technology. 2011; 41(7):699-731. doi: 10.1080/10643380903140224

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.

Publicaciones > Nuñez et al

European Journal of Organic Chemistry. 2011; 2011(7):1280 -1290. doi: 10.1002/ejoc.201001373

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.

Publicaciones > Cañeque et al

European Journal of Organic Chemistry. 2010; 2010(33):6323-6330. doi: 10.1002/ejoc.201000816

Heteroaromatic Cation-Based Chromophores: Synthesis and Nonlinear Optical Properties of Alkynylazinium Salts

Tatiana Cañeque, Ana M. Cuadro, Julio Alvarez-Builla, Javier Pérez-Moreno, Koen Clays, Gema Marcelo, Francisco Mendicuti, Obis Castaño, José L. Andrés, Juan J. Vaquero

Palabras clave: Heterocycles; Cations; Chromo­phores; Synthesis; Nonlinear ­optics

Resumen

Abstract A variety of alkynylazinium cationic (D-π-A%@2B) chromophores were prepared in good yields by the reaction of bromoazinium (pyridinium, quinolinium, and isoquinolinium iodides) with alkynes under Sonogashira conditions. The analysis of the experimentally recorded spectra is supported by quantum chemical calculations using restricted configuration interaction and density functional methods. First-order hyperpolarizabilities of (D-π-A%@2B) azinium-based cations as a new class of second-order nonlinear optical (NLO) chromophores were also studied by hyper-Rayleigh scattering experiments and computational procedures.

Publicaciones > Baeza et al

European Journal of Organic Chemistry. 2010; 2010(29):5607-5618. doi: 10.1002/ejoc.201000599

Application of Selective Palladium-Mediated Functionalization of the Pyrido%@5B3′,2′:4,5%@5Dpyrrolo%@5B1,2-c%@5Dpyrimidine Heterocyclic System for the Total Synthesis of Variolin B and Deoxyvariolin B

Alejandro Baeza, Javier Mendiola, Carolina Burgos, Julio Alvarez-Builla, Juan J. Vaquero

Palabras clave: Cross-coupling; Total synthesis; Natural products; Heterocycles

Resumen

Abstract The reaction of protected 3-bromo-2-(bromomethyl)-4-methoxypyrrolo%@5B2,3-b%@5Dpyridine and tosylmethyl isocyanide (TosMIC) afforded a pyrido%@5B3?,2?:4,5%@5Dpyrrolo%@5B1,2-c%@5Dpyrimidine derivative in good yield. This compound was transformed through installation of the pyrimidine moiety in the C5 position, hydrolysis, and decarboxylation in an advanced intermediate for the total or formal synthesis of the naturalalkaloid variolin B. Reaction of 3-bromo-2-(bromomethyl)-4-chloropyrrolo%@5B2,3-b%@5Dpyridine with N-tosylmethyl dichloroformimide as a synthetic TosMIC equivalent afforded trihalo-substituted pyrido%@5B3?,2?:4,5%@5Dpyrrolo%@5B1,2-c%@5Dpyrimidine. This compound was used in a new total synthesis of the alkaloid variolin B by selective and sequential C?N, C?C, and C?O palladium-mediated functionalization at the C9, C5, and C4 positions of the pyrido%@5B3?,2?:4,5%@5Dpyrrolo%@5B1,2-c%@5Dpyrimidine system. A formal synthesis of deoxyvariolin B is also described by using the same synthetic strategy.

Publicaciones > Deligeorgiev et al

Phosphorus, Sulfur, and Silicon and the Related Elements. 2010; 185(11):2292-2302. doi: 10.1080/10426501003598648

Novel Green Procedure for the Synthesis of 2-Arylbenzothiazoles Under Microwave Irradiation in Peg 200 Or Peg 400

Todor G. Deligeorgiev, Stefka Kaloyanova, Aleksey Vasilev, Juan J. Vaquero

Resumen

An improved green procedure for the synthesis of 2-aryl- and 2-hetarylbenzothiazoles by condensation of equivalent amounts of 2,2?-diaminodiphenyldisulfides or 2-aminothiophenols and various aromatic aldehydes in PEG 200/400 under microwave irradiation has been developed. This method allows the synthesis of 2-arylbenzothiazoles in high yields and with high purity regardless of the state of the starting compounds (liquid or solid) or the nature of the substituents in the aromatic ring.

Publicaciones > Deligeorgiev et al

Coloration Technology. 2010; 126(2):55-80. doi: 10.1111/j.1478-4408.2010.00235.x

Styryl dyes – synthesis and applications during the last 15 years

Todor Deligeorgiev, Aleksey Vasilev, Stefka Kaloyanova, Juan J Vaquero

Resumen

One of the most widely used and important groups of functional dyes are the styryl dyes and a review of this functional dye class has not been published for more than 15?years. In this review article, we describe the new trends in the synthesis of a range of novel intermediates and styryl dyes and include the most interesting examples of their high-tech applications. However, this review is not intended to be comprehensive because of the large number of styryl dye studies that have been carried out in this time. Styryl cyanine dyes are widely used in optical recording media in laser discs, as flexible dyes, laser dyes, as optical sensitisers and in various other fields, for example dye-sensitised solar cells and dyes with non-linear optical properties. Additionally, the most important applications for these dyes are in bio-labelling and in medicinal analysis.