gem-selective cross-dimerization and cross-trimerization of alkynes with silylacetylenes promoted by a Rhodium-Pyridine-N-heterocyclic carbene catalyst

The gem-selective cross-dimerization and -trimerization of silylacetylenes with alkynes through C[BOND]H activation using a rhodium(I)–pyridine–N-heterocyclic carbene catalyst have been developed. This reaction is applied to various aliphatic or aromatic terminal alkynes, internal alkynes, and gem-1,3-disubsituted enynes to afford the corresponding enynes and dienynes with high regio- and stereoselectivities and in good isolated yields (up to 91 %).Financial support from the Spanish Ministerio de Economía y Competitividad (MEC/FEDER) of Spain Project (CTQ2010-15221), the Diputación General de Aragón (E07), the KFUPMUNIZAR agreement, and CONSOLIDER INGENIO-2010, under the Project MULTICAT (CSD2009-00050) are gratefully acknowledged. L. R.-P. thanks CONACyT (Mexico, 186898 and 204033) for a postdoctoral fellowship.Peer Reviewe

Rhodium(I)-N-heterocyclic carbene catalyst for selective coupling of N-vinylpyrazoles with alkynes via C-H activation

The complex [Rh(μ-Cl)(IPr)(η2-coe)]2 {IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-carbene, coe = cis-cyclooctene} efficiently catalyzes the coupling of alkynes and N-vinylpyrazole via C–H activation, leading to Markovnikov-selective butadienylpyrazole derivatives under mild conditions. A straightforward approach to cross-conjugated acyclic trienes is also operative through a one-pot alkyne dimerization-hydrovinylation tandem reaction. The proposed mechanism involves C–H activation of vinylpyrazole directed by nitrogen coordination to the metallic center. Subsequent alkyne coordination, insertion, and reductive elimination steps lead to the coupling products. Several key intermediates participating in the catalytic cycle have been detected and characterized, including a κ-N, η2-C═C coordinated vinylpyrazole complex and a RhIII-hydride-alkenyl species resulting from the C–H activation of the vinylpyrazole.Financial support from the Spanish Ministerio de Economía y Competitividad (MEC/FEDER) of Spain Projects (CTQ2010-15221), the Diputación General de Aragón (E07), the ARAID Foundation, and CONSOLIDER INGENIO-2010, under the Project MULTICAT (CSD2009-00050) are gratefully acknowledged. L. R.-P. thanks CONACyT (Mexico, 186898 and 204033) for a postdoctoral fellowship.Peer Reviewe

Effects of the Menstrual Cycle on Jumping, Sprinting and Force-Velocity Profiling in Resistance-Trained Women: A Preliminary Study

The aim of this study was to examine the effects of the menstrual cycle on vertical jumping, sprint performance and force-velocity profiling in resistance-trained women. A group of resistancetrained eumenorrheic women (n = 9) were tested in three phases over the menstrual cycle: bleeding phase, follicular phase, and luteal phase (i.e., days 1–3, 7–10, and 19–21 of the cycle, respectively). Each testing phase consisted of a battery of jumping tests (i.e., squat jump [SJ], countermovement jump [CMJ], drop jump from a 30 cm box [DJ30], and the reactive strength index) and 30 m sprint running test. Two different applications for smartphone (My Jump 2 and My Sprint) were used to record the jumping and sprinting trials, respectively, at high speed (240 fps). The repeated measures ANOVA reported no significant differences (p ≥ 0.05, ES < 0.25) in CMJ, DJ30, reactive strength index and sprint times between the different phases of the menstrual cycle. A greater SJ height performance was observed during the follicular phase compared to the bleeding phase (p = 0.033, ES = −0.22). No differences (p ≥ 0.05, ES < 0.45) were found in the CMJ and sprint force-velocity profile over the different phases of the menstrual cycle. Vertical jump, sprint performance and the force-velocity profiling remain constant in trained women, regardless of the phase of the menstrual cycle.Pre-competitive Projects for Early Stage Researchers Programme from the University of Granada (ref: PPJIA2020.03

Clima escolar y percepciones del profesorado tras la implementación de un programa de convivencia escolar

En este estudio se evalúa la percepción del clima escolar de dos grupos de profesores de dos centros educativos. El primer grupo (grupo experimental) ha implantado un programa de convivencia escolar, el otro (grupo de control) no. En esta investigación participaron 48 profesores que cumplimentaron la Escala de Percepción del Clima y del Funcionamiento del Centro (24 del centro experimental y 24 del centro que sirvió como grupo de control). Se encontraron diferencias estadísticamente significativas a favor del centro experimental en diferentes ítems de la escala, así como en dos de los seis factores evaluados. En líneas generales, los docentes perciben un mejor clima y un mejor funcionamiento en el centro experimental.The aim of this work was to assess the perceptions about school climate in two groups of teachers from two different primary schools. The first group (experimental group) has implemented a program of school coexistence, the other (control group) did not. This research involved 48 teachers who completed the Perception Scale Climate (24 from experimental center and 24 from control group). Statistically significant differences were found in favor of experimental center. Differences between the experimental center and control group were found in different scale items, as well as in two of the six evaluated factors. In general, teachers from the experimental group perceived better school climate than teachers from control group

A new access to 4 H-quinolizines from 2-vinylpyridine and alkynes promoted by rhodium-N-heterocyclic-carbene catalysts

Forging the lock that autolocks! Rh-NHC catalysts promote a new access to 4 H-quinolizine species from 2-vinylpyridine and terminal and internal alkynes through C-H activation and C-C coupling reactions (see figure). N-Bridgehead heterocycle formation is favored for internal- over terminal-substituted butadienylpyridine derivatives in a thermal 6π-electrocyclization process. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Financial support from the Ministerio de Economía y Competitividad of Spain Project CTQ2010–15221), the Diputación General de Aragón (E07), the ARAID Foundation under the program “Jóvenes Investigadores”, and CONSOLIDER INGENIO-2010, under the Project MULTICAT (CSD2009–00050) are gratefully acknowledged.Peer Reviewe

Rhodium (I)-N-heterocyclic carbene catalyst for selective coupling of aromatic heterocycles with olefins and alkynes by C-H activation

Resumen del póster presentado al Organometallic Chemistry Directed Towards Organic Synthesis (OMCOS) IUPAC International Symposium, celebrado en Sitges-Barcelona (España) del 28 de junio al 2 de julio de 2015.The development of new and selective catalytic methodologies has been the focus of intense research. Particularly, rhodium catalyzed C-C bond formation via C-H activation continues to be a powerful tool in organic shynthesis. Substitution of classical ligands such as phosphines by NHC carbene ligands in the metal center has a significant influence on the selectivity control over the catalytic outcome. Herein, we present the selective coupling of heteroarenes with alkenes and alkynes mediated by a Rh[sup]I[/sup]-NHC catalyst. The proposed mechanism involves C-H activation, migratory insertion reactions and reductive elimination steps (Scheme 1 - Control of selectivity in the aromatic heterocycles functionalization).Peer Reviewe

Pyridine-enhanced head-to-tail dimerization of terminal alkynes by a rhodium-N-heterocyclic-carbene catalyst

A general regioselective rhodium-catalyzed head-to-tail dimerization of terminal alkynes is presented. The presence of a pyridine ligand (py) in a Rh-N-heterocyclic-carbene (NHC) catalytic system not only dramatically switches the chemoselectivity from alkyne cyclotrimerization to dimerization but also enhances the catalytic activity. Several intermediates have been detected in the catalytic process, including the π-alkyne-coordinated RhI species [RhCl(NHC)(η2-HC ≡CCH2Ph)(py)] (3) and [RhCl(NHC){η2-C(tBu) ≡C(E)CH=CHtBu}(py)] (4) and the RhIII-hydride-alkynyl species [RhClH{-C ≡CSi(Me) 3}(IPr)(py)2] (5). Computational DFT studies reveal an operational mechanism consisting of sequential alkyne Ci£ H oxidative addition, alkyne insertion, and reductive elimination. A 2,1-hydrometalation of the alkyne is the more favorable pathway in accordance with a head-to-tail selectivity.Financial support from the Spanish Ministerio de Economía y Competitividad (MEC/FEDER) Projects (CTQ2010-15221, CTQ2012-35665), the Diputación General de Aragón (E07), the ARAID Foundation under the program “Jóvenes Investigadores”, and CONSOLIDER INGENIO-2010 under the Project MULTICAT (CSD2009-00050) is gratefully acknowledged. L.R.-P. thanks CONACyT (Mexico, 186898) for a postdoctoral fellowship.Peer Reviewe

Divergent reactivity of 2-vinylpyridine and 1-vinylpyrazole in rhodium-phosphine systems: C-H activation and dinuclear chemistry

[EN]: The RhI-RhIII mixed valence dinuclear complex Rh2- Cl2(μ-H)(μ-η2,κ2-C,N-NC5H4-2-(Z)CH=CH)(PPhMe2)3 has been prepared by reaction of [Rh(μ-Cl)(η2-coe)2]2 with 2-vinylpyridine in the presence of dimethylphenylphosphine as a result of C-H activation of the terminal olefinic proton. The X-ray structure presents anagostic Rh···HC and π-π interactions between aromatic rings. In contrast, 1-vinylpyrazole does not undergo a C-H activation process, resulting in the formation of dinuclear species supported by 1-vinylpyrazole bridges. Anagostic Rh···HC interactions and CH···Cl hydrogen bonds are responsible for the 3D packing of the complex.[ES]: El complejo dinuclear de valencia mixta RhI-RhIII Rh2-Cl2(μ-H)(μ-η2,κ2-C,N-NC5H4-2-(Z)CH=CH)(PPhMe2)3 ha sido preparado por reacción de [Rh(μ-Cl)(η2-coe)2]2 con 2-vinilpiridina en presencia de dimetilfenilfosfina, como resultado de la activación C-H del protón terminal de la olefina. La estructura de rayos-X presenta enlaces anagósticos Rh···HC, así como interacciones π-π entre anillos aromáticos. Por otro lado, la reacción con 1-vinilpirazol no da lugar a una activación C-H sino que se observa la formación de una especie dinuclear soportada por ligandos 1-vinilpirazol puente. Diferentes interacciones anagósticas Rh···HC y de enlace de hidrógeno CH···Cl son responsables del empaquetamiento tridimensional del complejo.Financial support from the Ministerio de Economía y Competitividad (MINECO/FEDER) of Spain (Proyect CTQ2013-42532-P), the Diputación General de Aragón and Fondo Social Europeo (DGA/FSE-E07), and CONSOLIDER INGENIO-2010 under the Project MULTICAT (CSD2009-00050) is gratefully acknowledged.Peer Reviewe

Preparation of butadienylpyridines by iridium-NHC-catalyzed alkyne hydroalkenylation and quinolizine rearrangement

Iridium(I) N-heterocyclic carbene complexes of formula Ir(κ2O,O’-BHetA)(IPr)(η2-coe) [BHetA=bis-heteroatomic acidato, acetylacetonate or acetate; IPr=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-carbene; coe=cyclooctene] have been prepared by treating Ir(κ2O,O’-BHetA)(η2-coe)2 complexes with IPr. These complexes react with 2-vinylpyridine to afford the hydrido-iridium(III)-alkenyl cyclometalated derivatives IrH(κ2O,O’-BHetA)(κ2N,C-C7H6N)(IPr) through the iridium(I) intermediate Ir(κ2O,O’-BHetA)(IPr)(η2-C7H7N). The cyclometalated IrH(κ2O,O’-acac)(κ2N,C–C7H6N)(IPr) complex efficiently catalyzes the hydroalkenylation of aromatic and aliphatic terminal alkynes and enynes with 2-vinylpyridine to afford 2-(4R-butadienyl)pyridines with Z,E configuration as the major reaction products (yield up to 89 %). In addition, unprecedented (Z)-2-butadienyl-5R-pyridine derivatives have been obtained as minor reaction products (yield up to 21 %) from the elusive 1Z,3gem-butadienyl hydroalkenylation products. These compounds undergo a thermal 6π-electrocyclization to afford bicyclic 4H-quinolizine derivatives that, under catalytic reaction conditions, tautomerize to 6H-quinolizine to afford the (Z)-2-(butadienyl)-5R-pyridine by a retro-electrocyclization reaction.Financial support from the Spanish Ministerio de Ciencia e Innovación (MICINN/FEDER) under Project PID2019-103965GB-I00, and the Departamento de Ciencia, Universidad y Sociedad del Conocimiento del Gobierno de Aragón (group E42_20R) is gratefully acknowledged. I.G. thanks the Humboldt Foundation for a research fellowship.Peer reviewe