Institute Investigaciones Quimicas Csic Us

Sevilla, Spain

Institute Investigaciones Quimicas Csic Us

Sevilla, Spain

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Ros A.,Institute Investigaciones Quimicas Csic Us | Fernandez R.,University of Seville | Lassaletta J.M.,Institute Investigaciones Quimicas Csic Us
Chemical Society Reviews | Year: 2014

The direct borylation of hydrocarbons via C-H activation has reached an impressive level of sophistication and efficiency, emerging as a fundamental tool in synthesis because of the versatility offered by organoboron compounds. As a remarkable particularity, the catalytic systems originally developed for these reactions are relatively insensitive to directing effects, and the regioselectivity of the borylations is typically governed by steric factors. Likely stimulated by the great synthetic potential of the expected functionalised organoboranes, however, many groups have recently focused on the development of complementary strategies for directed, site-selective borylation reactions where a directing group controls the course of the reaction. In this tutorial review, the different strategies and findings related to the development of these directed borylation reactions via C(sp2)-H or C(sp3)-H activation will be summarized and discussed. © 2014 the Partner Organisations.


Ros A.,Institute Investigaciones Quimicas Csic Us | Estepa B.,University of Seville | Lopez-Rodriguez R.,Institute Investigaciones Quimicas Csic Us | Alvarez E.,Institute Investigaciones Quimicas Csic Us | And 2 more authors.
Angewandte Chemie - International Edition | Year: 2011

The hemilabile character of 2-pyridyl carbaldehyde hydrazones as N,N bidentate ligands is key to performing regioselective Ir III-catalyzed ortho borylations of 2-aryl pyridines(isoquinolines) and aromatic N,N-dimethylhydrazones (see scheme; pin=pinacol, Bn=benzyl). Internal "ate" complexes or products free from N-B interactions are formed depending on the steric properties of the substrates. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Monge D.,University of Seville | Daza S.,University of Seville | Bernal P.,Institute Investigaciones Quimicas Csic Us | Fernandez R.,University of Seville | Lassaletta J.M.,Institute Investigaciones Quimicas Csic Us
Organic and Biomolecular Chemistry | Year: 2013

The unprecedented diaza-ene reaction of formaldehyde N-tert-butyl hydrazone with nitroalkenes can be efficiently catalyzed by an axially chiral bis-thiourea to afford the corresponding diazenes in good to excellent yields (60-96%) and moderate enantioselectivities, up to 84 : 16 er; additional transformation of diazenes into their tautomeric hydrazones proved to be operationally simple and high-yielding, affording bifunctional compounds which represent useful intermediates for the synthesis of enantioenriched β-nitro-nitriles and derivatives thereof. © 2013 The Royal Society of Chemistry.


Bernal P.,Institute Investigaciones Quimicas Csic Us | Fernandez R.,University of Seville | Lassaletta J.M.,Institute Investigaciones Quimicas Csic Us
Chemistry - A European Journal | Year: 2010

(Figure Presented) New catalyst, new reaction: The unprecedented cyanosilylation of nitroalkenes can be efficiently catalyzed by a bifunctional quinine derivative with tetraalkylammonium cyanide and thiourea moieties. The activation of the nitroalkene by hydrogen bonding to the thiourea, together with the presence of an "active" cyanide, provides new mode of activation that leads to products in high yields and good selec tivities (see scheme). © 2010 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim.


Angulo J.,Institute Investigaciones Quimicas Csic Us | Enriquez-Navas P.M.,Laboratory of GlycoNanotechnology | Nieto P.M.,Institute Investigaciones Quimicas Csic Us
Chemistry - A European Journal | Year: 2010

The direct evaluation of dissociation constants (KD) from the variation of saturation transfer difference (STD) NMR spectroscopy values with the receptor-ligand ratio is not feasible due to the complex dependence of STD intensities on the spectral properties of the observed signals. Indirect evaluation, by competition experiments, allows the determination of K D, as long as a ligand of known affinity is available for the protein under study. Herein, we present a novel protocol based on STD NMR spectroscopy for the direct measurements of receptorligand dissociation constants (K D) from single-ligand titration experiments. The influence of several experimental factors on STD values has been studied in detail, confirming the marked impact on standard determinations of proteinligand affinities by STD NMR spectroscopy. These factors, namely, STD saturation time, ligand residence time in the complex, and the intensity of the signal, affect the accumulation of saturation in the free ligand by processes closely related to fast protein-ligand rebinding and longitudinal relaxation of the ligand signals. The proposed method avoids the dependence of the magnitudes of ligand STD signals at a given saturation time on spurious factors by constructing the binding isotherms using the initial growth rates of the STD amplification factors, in a similar way to the use of NOE growing rates to estimate cross relaxation rates for distance evaluations. Herein, it is demonstrated that the effects of these factors are cancelled out by analyzing the protein-ligand association curve using STD values at the limit of zero saturation time, when virtually no ligand rebinding or relaxation takes place. The approach is validated for two well-studied protein-ligand systems: the binding of the saccharides GIcNAc and GIcNAcβl,4GIcNAc (chitobiose) to the wheat germ agglutinin (WGA) lectin, and the interaction of the amino acid L-tryptophan to bovine serum albumin (BSA). In all cases, the experimental KD measured under different experimental conditions converged to the thermodynamic values. The proposed protocol allows accurate determinations of protein-ligand dissociation constants, extending the applicability of the STD NMR spectroscopy for affinity measurements, which is of particular relevance for those proteins for which a ligand of known affinity is not available. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim binding constants binding isotherms. dissociation constants. NMR spectroscopy. proteins.


Grirrane A.,Polytechnic University of Valencia | Garcia H.,Polytechnic University of Valencia | Corma A.,Polytechnic University of Valencia | Alvarez E.,Institute Investigaciones Quimicas Csic Us
ACS Catalysis | Year: 2011

Bulky Au(I) biphenylphosphine complexes form with phenylacetylene isolable digold complexes under conditions of the room-temperature intermolecular [2 + 2] cycloaddition of phenylacetylene and α-methylstyrene. Single-crystal X-ray diffraction (XRD) of two digold complexes show the presence of Au atoms connected to the C≡C triple bond of a phenylacetylene subunit through a σ and a π bond. The two Au atoms are fluxional and undergo exchange even at -80 °C. These digold complexes exhibit as catalysts almost complete selectivity toward the intermolecular cycloaddition and higher final yield to the corresponding cyclobutene than the corresponding mono Au(I) complex precursor. The difference in selectivity between the commercial mono Au(I) complex and the corresponding digold-phenylacetylene complex was found to be due to the generation of Brönsted acids of the counteranion [HSbF6 or HN(CF3SO2)2 in the cases studied] that are formed by replacement of the C≡C-H by a C≡C-Au bond. This Brönsted acid causes α-methylstyrene dimerization and degradation of the cyclobutene, two processes that do not occur when the reaction is promoted by the digold complex. © 2011 American Chemical Society.


Grirrane A.,Polytechnic University of Valencia | Garcia H.,Polytechnic University of Valencia | Corma A.,Polytechnic University of Valencia | Alvarez E.,Institute Investigaciones Quimicas Csic Us
Chemistry - A European Journal | Year: 2012

Two birds, one nanoparticle: A highly efficient and selective tandem reaction comprising C-N and C-C cross-coupling of iodoanilines to form styrylguanidines by using a recyclable, heterogeneous, supported palladium nanoparticle catalyst is reported (see scheme). A mechanistic proposal based on coordination of palladium nanoparticles to the basic N atoms of aniline and guanidine is supported by isolation of palladium complexes with aniline or guanidine. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Grirrane A.,Polytechnic University of Valencia | Alvarez E.,Institute Investigaciones Quimicas Csic Us | Garcia H.,Polytechnic University of Valencia | Corma A.,Polytechnic University of Valencia
Angewandte Chemie - International Edition | Year: 2014

Care should be exercised when using CH2Cl2 as a solvent for reactions in which amines are a reagent, since undesirable deactivation of cationic copper(I) and gold(I) catalysts to form the corresponding inactive neutral chloride complexes [LMCl] (M=Cu or Au) can occur as a result of the generation of hydrogen chloride in the medium. CuI and AuI deactivation has been proved for the Mannich three-component coupling reaction. A series of CuI and AuI complexes with potential mechanistic implications were isolated and characterized by X-ray crystallography. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Grirrane A.,Polytechnic University of Valencia | Garcia H.,Polytechnic University of Valencia | Corma A.,Polytechnic University of Valencia | Alvarez E.,Institute Investigaciones Quimicas Csic Us
Chemistry - A European Journal | Year: 2013

Two for one gold: Factors governing the formation of isolable digold(I) σ,π-acetylide complexes are given (see scheme), indicating the general tendency of phosphine-AuI precatalysts to form this type of complexes, which are involved as reaction intermediates in gold(I)-catalyzed reactions. Mechanistic insights into the intermolecular hydroamination of aniline and terminal alkynes catalyzed by gold(I) have shown the role of a fluxional, cationic σ,π-digold alkynide complex as one of the intermediates in the formation of imines. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Grirrane A.,Polytechnic University of Valencia | Garcia H.,Polytechnic University of Valencia | Alvarez E.,Institute Investigaciones Quimicas Csic Us
Beilstein Journal of Organic Chemistry | Year: 2013

In the context of palladium-catalyzed guanylation of anilines herein, we have been able to characterize and isolate bis(anilino) and bis(guanidino)Pd(II) complexes using reaction conditions under which stoichiometric amounts of palladium salts are used. Characterization of these palladium complexes strongly supports a mechanistic proposal for the catalytic guanylation of anilines using PdCl2 (NCCH3)2 as catalyst that involves the intermediacy of these Pd(II) complexes. © 2013 Grirrane et al.

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