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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. Source


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. Source


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. Source


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. Source


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. Source

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