Mechanistic Studies on Gold-Catalyzed Direct Arene C–H Bond Functionalization by Carbene Insertion: The Coinage-Metal Effect

The catalytic functionalization of the Csp 2-H bond of benzene by means of the insertion of the CHCO2Et group from ethyl diazoacetate (N2=CHCO2Et) has been studied with the series of coinage metal complexes IPrMCl (IPr = IPr = 1,3-bis(diisopropylphenyl)imidazol-2-ylidene) and NaBArF 4 (BArF 4 = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate). For Cu and Ag, these examples constitute the first of such metals toward this transformation, that also provides ethyl cyclohepta-2,4,6-trienecarboxylate as by-product from the so-called Buchner reaction. In the case of methyl-substituted benzenes, the reaction exclusively proceeds onto the aromatic ring, the Csp 3-H bond remaining unreacted. A significant coinage metal effect has been observed, since the gold catalyst favors the formation of the insertion product into Csp 2-H bond whereas copper and silver preferentially induce the formation of the cycloheptatriene derivative. Experimental studies and theoretical calculations have explained the observed selectivity in terms of the formation of a common Wheland intermediate, resembling an electrophilic aromatic substitution, from which the reaction pathway evolves into two separate routes to each product.We thank the Spanish MINECO for CTQ2014-52769-C3-1-R, CTQ2014-57761-R, RED INTECAT CTQ2014-52974-REDC and Severo Ochoa Excellence Accreditation 2014-2018 SEV-2013-0319 and the ICIQ Foundation for financial support

A Quantitative Model for Alkane Nucleophilicity Based on C−H Bond Structural/Topological Descriptors

A first quantitative model for calculating the nucleophilicity of alkanes is described. A statistical treatment was applied to the analysis of the reactivity of 29 different alkane C−H bonds towards in situ generated metal carbene electrophiles. The correlation of the recently reported experimental reactivity with two different sets of descriptors comprising a total of 86 parameters was studied, resulting in the quantitative descriptor‐based alkane nucleophilicity (QDEAN) model. This model consists of an equation with only six structural/topological descriptors, and reproduces the relative reactivity of the alkane C−H bonds. This reactivity can be calculated from parameters emerging from the schematic drawing of the alkane and a simple set of sums.We thank MINECO for support with Grants CTQ2017-82893-C2- 1-R, CTQ2015-73693-JIN, CTQ2017-87792-R and Red Intecat (CTQ2016-81923-REDC). Junta de Andalucía is also acknowledged for Grant P12-FQM-1765. R. G. and A. O. thank MINECO for FPI and Juan de la Cierva fellowships, respectively

Pensar, sentir y hacer la escuela secundaria posible

Fil: Ferreyra, Horacio Ademar. Universidad Católica de Córdoba. Facultad de Educación; Argentin

Escuela secundaria posible

Fil: Ferreyra, Horacio Ademar. Universidad Católica de Córdoba. Facultad de Educación; Argentin

Escuela secundaria posible

REPENSAR LA EDUCACIÓN SECUNDARIA Colección de infografías II Parte Seguimiento de medios de comunicación 2017-2019Fil: Ferreyra, Horacio Ademar. Universidad Católica de Córdoba. Facultad de Educación; ArgentinaFil: Di Francesco, Adriana Carlota. Universidad Católica de Córdoba. Facultad de Educación; ArgentinaFil: Equipo de investigación en educación de adolescentes y jóvenes. Unidad Asociada CONICET. Universidad Católica de Córdoba. Facultad de Educación; Argentina

Two Copper-Carbenes from One Diazo Compound

Many transition-metal complexes MLn decompose diazo compounds N2-CR1R2 generating metal-carbenes LnM-CR1R2 which transfer the carbene group to other substrates, constituting an important tool in organic synthesis. All previous reports have shown that the CR1R2 fragment at the metal-carbene remains intact from the parent diazo compound. Herein we report the detection and isolation of a monosubstituted copper carbene where the CR1R2 ligand has undergone a modification from the initial diazo reagent. When TpMsCu(THF) (TpMs = hydrotris(3-mesityl)pyrazolylborate ligand) was reacted with N,N-diethyl diazoacetamide [N2-C(H)(CONEt2)], the stable copper carbene TpMsCu-C(H)(NEt2) was isolated, resulting from a decarbonylation process, with carbon monoxide being trapped as TpMsCu(CO). The simultaneous observation of products derived from the intramolecular carbene insertion reaction into C–H bonds demonstrates that the expected TpMsCu-C(H)(CONEt2) complex is also formed. Experimental data, DFT calculations, and microkinetic models allow us to propose that the latter undergoes CO loss en route to the former.We dedicate this work to the memory of Professor Victor Riera, one of the pioneers of organometallic chemistry in Spain. We acknowledge financial support from the Ministerio de Ciencia e Innovación (CTQ2017-82893-C2-1-R, CTQ2017- 87792-R, P. O. Feder UHU-1260216 and P. O. Feder UHU- 1254043, and Red Intecat CTQ2016-81923-REDC)Funding for open access charge: Universidad de Huelva / CBUAFunding for open access charge: Universidad de Huelva / CBU

Implementació de l'avaluació de competències transversals i específiques

En el marc de l'EEES el procés d'aprenentatge dels estudiant s'avalua per mitjà de l'assoliment de competències. La transició d'un model docent basat en el professor vers un model centrat en l'estudiant té una certa complexitat, degut al bagatge dels professors i la manca d'eines per a avaluar competències de manera sistemàtica. En l'article presentem la implementació de l'avaluació per competències en una assignatura del grau d'Informació i Documentació de la UOC mitjançant l'eina Rubrick.In the context of the EHEA, the student learning process is evaluated using competency-based assessment. The move from a teaching model focusing on the teacher to a student-centred model is somewhat complex given the baggage the teachers bring with them and the lack of tools to assess competencies systematically. This article presents how competency-based assessment using the Rubrick to

Intermolecular Allene Functionalization by Silver-Nitrene Catalysis

Under silver catalysis conditions, using [Tp*,BrAg]2 as the catalyst precursor, allenes react with PhI═NTs in the first example of efficient metal-mediated intermolecular nitrene transfer to such substrates. The nature of the substituent at the allene seems crucial for the reaction outcome since arylallenes are converted into azetidine derivatives, whereas methylene aziridines are the products resulting from alkylallenes. Mechanistic studies allow proposing that azetidines are formed through unstable cyclopropylimine intermediates, which further incorporate a second nitrene group, both processes being silver-mediated. Methylene aziridines from alkylallenes derive from catalytic nitrene addition to the allene double bonds. Both routes have resulted to be productive for further synthetic transformations affording aminocyclopropanes.Support for this work was provided by the MINECO (CTQ2017-82893-C2-1-R, CTQ2017-87792-R and Red Intecat CTQ2016-81923-REDC) and Universidad de Huel va (PO FEDER 2014-2020-UHU-1254043). MR thanks MINECO for a predoctoral fellowship

Mechanism for Hydride-Assisted Rearrangement from Ethylidene to Ethylene in Iridium Cationic Complexes

6 páginas, 3 figuras, 5 esquemas.The cationic hydride alkylidene complexes [TpMe2Ir(═CH−CH3)(H)(PMe3)]+ and [Cp*Ir(═CH−CH3)(H)(PMe3)]+ (TpMe2 = hydrotris(3,5-dimethyl-1-pyrazolyl)borate; Cp* = pentamethylcyclopentadienyl) are experimentally known to tautomerize to the corresponding hydride alkene species. Our computational study on the mechanism shows that the reaction takes place through formation of the corresponding alkyl intermediates, with participation of species involving α- and β-CH agostic interactions. Computed energy barriers reproduce the available experimental kinetic data and agree with a much faster process in the Cp* system. The highest stabilization of the hydride alkylidene complex (the reactant) in the TpMe2 system appears as the main reason for the higher barrier found. The difference between the two complexes is due to the steric effects of the spectator ligands.We thank the ICIQ Foundation, the Spanish Ministerio de Ciencia e Innovacion (Consolider Ingenio 2010 CSD2006-0003 and CSD2007-000006; projects CTQ2007-62814, CTQ2008-06866-CO2-01/BQU, CTQ2008-06866-CO2-02/BQU, and CTQ2008-03077/BQU, FEDER support), Generalitat de Catalunya (grants 2009SGR0259 and XRQTC), and Junta de Andalucia (project numbers FQM-315 and FQM-67). M.B. thanks the Spanish Ministerio de Ciencia e Innovacion for a “Juan de la Cierva” grant.Peer reviewe

Mechanism for Hydride-Assisted Rearrangement from Ethylidene to Ethylene in Iridium Cationic Complexes

6 páginas, 3 figuras, 5 esquemas.The cationic hydride alkylidene complexes [TpMe2Ir(═CH−CH3)(H)(PMe3)]+ and [Cp*Ir(═CH−CH3)(H)(PMe3)]+ (TpMe2 = hydrotris(3,5-dimethyl-1-pyrazolyl)borate; Cp* = pentamethylcyclopentadienyl) are experimentally known to tautomerize to the corresponding hydride alkene species. Our computational study on the mechanism shows that the reaction takes place through formation of the corresponding alkyl intermediates, with participation of species involving α- and β-CH agostic interactions. Computed energy barriers reproduce the available experimental kinetic data and agree with a much faster process in the Cp* system. The highest stabilization of the hydride alkylidene complex (the reactant) in the TpMe2 system appears as the main reason for the higher barrier found. The difference between the two complexes is due to the steric effects of the spectator ligands.We thank the ICIQ Foundation, the Spanish Ministerio de Ciencia e Innovacion (Consolider Ingenio 2010 CSD2006-0003 and CSD2007-000006; projects CTQ2007-62814, CTQ2008-06866-CO2-01/BQU, CTQ2008-06866-CO2-02/BQU, and CTQ2008-03077/BQU, FEDER support), Generalitat de Catalunya (grants 2009SGR0259 and XRQTC), and Junta de Andalucia (project numbers FQM-315 and FQM-67). M.B. thanks the Spanish Ministerio de Ciencia e Innovacion for a “Juan de la Cierva” grant.Peer reviewe