Revisiting the mechanism of the mono nuclear copper-catalyzed cycloaddition of azide and alkynes (CuAAC) by the topology of ....

Comunicación presentada y aceptada en el CHITEL2013, XXXIX International Conference THEORETICAL CHEMISTS OF LATIN EXPRESSION (XXXIX Congreso Internacional de Químicos de Expresión Latina).Se analiza el mecanismo de la reacción de cicloadición, catalizada por Cu(I), de azidas a alquinos (CuAAC), haciendo uso de métodos DFT y de herramientas de análisis de la densidad electrónica basadas en la topología de su laplaciana

Exploring the regioselectivity for the cycloaddition of azides to alkynes catalyzed by dinuclear copper clusters (Cu2AAC) with the topology of 2rho(r) and 2rho(r)

This study constitutes an extension of a previous research on the regioselectivity of the copper catalyzed cycloaddition of azides to alkynes (1) (the CuAAC reaction) by Quantum Chemical Topological methods. In particular, by following the evolution the topology of the laplacian of the electronic charge density and its gradient vector field along the reaction coordinates, computed with different Density Functionals (B3LYP, LCwPBE, M06-L, wB97XD, and M06-2X) and 6-311++G(d,p) basis set. For the mononuclear process, we found that a H-type interaction conditions the attack of the azide in the 1,5-CuAAC. In addition, given that experimental evidences (2) seem to suggest the participation of a second Cu atom in the reaction coordinate, we have explored very recently (3) the mechanism involving a dinuclear copper cluster at the LCwPBE/6-311++G(d,p) level. Interestingly, the catalyst modifies the uncatalyzed Huisgen mechanism, by inducing sequentially first the terminal N-C bond and the internal afterwards in a concerted fashion for the 1,4-CuAAC and stepwise for the 1,4-Cu2AAC. Furthermore, as seen in the topology of the laplacian, the catalyst provoked that a carbon acts as a nucleophile and turned pericyclic mechanism into pseudopericyclic (3). [1] Calvo-Losada S., Pino M.S. and Quirante J.J., J. Mol.Model., 20, 2187 (2014) [2] Worrell B. T., Malik J. A. and Fokin V. V., Science, 340, 457 (2013) [3] Calvo-Losada S., Pino M.S. and Quirante J.J., J. Phys.Chem. B, 119,1243 (2015)Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Intramolecular [3+2] Cycloaddition of Fused Azolo-Azepanes from Azido Monosaccharides Derivatives

Síntesis de bicíclicos compuestos empleando epoxiamidas como material de partida. Obtención de tetrazolo azepanos con posible actividad biológica.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Intramolecular [3+2] cycloaddition of azido-unsaturated esters derived of monosaccharides

Iminosugars have been shown to be very potent inhibitors of glycosidases and glycolsyltransferases. Due to their ability to resemble the transition states of the sugars involved in these processes, a variety of m onocyclic and bicyclic iminosugars have been synthesized or isolated from natural sources over the years. As part of our ongoing work on the preparation of glycosidase inhibitors , we developed stereoselective methods for synthesizing iminosugars from 2,3-epoxyamides obtained from monosaccharides.Now, we are interested in the syntheses of novel bicyclic triazoles, by intramolecular cycloaddition, due to the possibility of combining azido group and unsaturated esters in the same molecule. The triazole system is broadly considered in syntheses of bioactive products and the option of fused iminosugar with triazole has been evaluated. Firstly, we started with a less complex azido derivative 2a to continue with azido compounds 2b obtained from our 2,3-epoxyamides 3, by regioselective introduction of an azido group. The fused triazolines 4a were formed by heating of 2a. Aromatization of 4a afforded byciclic triazoles. There are several possibilitie s in the cyclization process depending on the reaction conditions and products 5,6 and 7 can be formed. Moreover, we conducted a theoretical DFT based study of the cycloaddition to value the probability of formation of the triazoline 4a and subsequent aroma tization to triazole 1,versus elimination to the unsaturated ester 5Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Influence of the Incorporation of Basic or Amphoteric Oxides on the Performance of Cu-Based Catalysts Supported on Sepiolite in Furfural Hydrogenation

Cu-based catalysts supported on sepiolite have been tested in vapor-phase hydrogenation of furfural. The incorporation of basic or amphoteric metal oxides (magnesium oxide, zinc oxide, or cerium oxide) improves the catalytic behavior, reaching a maximum furfural conversion above 80% after 5 h of reaction at 210 ºC. In all cases, the main product is furfuryl alcohol, obtaining 2-methylfuran in lower proportions. The incorporation of these metal oxide species ameliorates the dispersion of metallic Cu nanoparticles, increasing the number of available Cu(0)-sites, which enhances the catalytic performance. The presence of acid sites favors the hydrogenolysis of furfuryl alcohol towards 2-methylfuran, although it also causes an increase of carbon species on its surface, which is associated with the catalytic deactivation of the catalyst along the time-on-stream.This research was funded by the Ministry of Economy and Competitiveness (Spain), grant numbers (CTQ2015-64226-C3-3-R, IEDI-2016-00743), Junta de Andalucía (Spain) (P12-RNM-1565), and FEDER (European Union) funds