Ediacaran Obduction of a Fore-Arc Ophiolite in SW Iberia: A Turning Point in the Evolving Geodynamic Setting of Peri- Gondwana

The Calzadilla Ophiolite is an ensemble of mafic and ultramafic rocks that represents the transition between lower crust and upper mantle of a Cadomian (peri-Gondwanan) fore arc. Mapping and structural analysis of the ophiolite demonstrates that it was obducted in latest Ediacaran times, because the Ediacaran-Early Cambrian sedimentary series (Malcocinado Formation) discordantly covers it. The ophiolite and emplacement-related structures are affected by Variscan deformation (Devonian-Carboniferous), which includes SW verging overturned folds (D1) and thrusts (D2), upright folds (D3), extensional faults (D4), and later faults (D5). These phases of deformation are explained in the context of Variscan tectonics as the result of the progressive collision between Gondwana and Laurussia. Qualitative unstraining of Variscan deformation reveals the primary geometry of Ediacaran-Cambrian structures and uncovers the generation of east verging thrusts as responsible for the primary obduction of the Calzadilla Ophiolite. Restoration of planar and linear structures associated with this event indicates an Ediacaran, east directed obduction of the ophiolite, that is, emplacement of the Cadomian fore arc onto inner sections of the northern margin of Gondwana. According to regional data, the obduction separates two extension-dominated stages in the tectonic evolution of the African margin of northern Gondwana preserved in southern Europe. Preobduction extension brought about the onset and widening of fore-arc and back-arc basins in the external part of the continent, while postobduction extension facilitated the formation of extensional migmatitic domes, an oceanward migration of back-arc spreading centers across peri-Gondwana, and the eventual opening of a major basin such as the Rheic Ocean

Peralkaline and alkaline magmatism of the Ossa-Morena zone (SW Iberia): Age, source, and implications for the Paleozoic evolution of Gondwanan lithosphere

The Ossa-Morena zone in SW Iberia represents a section of the northern margin of West Gondwana that formed part of a Cordilleran-type orogenic system during the Neoproterozoic (Cadomian orogeny). The crustal section in this zone preserves the record of rifting that led to the opening of the Rheic Ocean in the early Paleozoic and the collision of Gondwana and Laurussia in the late Paleozoic (Variscan orogeny). We present U-Pb zircon data from three alkaline to peralkaline syenites that intruded Neoproterozoic and Cambrian strata and give crystallization ages ranging between ca. 490 Ma and 470 Ma. Lu/Hf isotopic data from these zircons give positive initial εHf values (0 ≤ εHf(t) ≤ +11.5) that approach the model values for the depleted mantle at the time of crystallization. This suggests that a significant proportion of the magma was derived from the mantle, with limited mixing/assimilation with crustal-derived melts. Alkaline/peralkaline magmatic suites of similar age and chemical composition intruded other sections of the northern margin of West Gondwana and along the boundaries of the continental blocks that today make up Iberia. These blocks are further characterized by the presence of high-pressure metamorphic belts that formed during accretion and subsequent collision of peri-Gondwanan domains against Laurussia during the Devonian and Carboniferous (Variscan orogeny). Our U-Pb and Lu-Hf data set indicates that during the Cambrian−Ordovician transition, lithosphere extension reached a stage of narrow intracontinental rifting, where deeply sourced magmas, probably coming from the lower crust and/or the upper mantle, intruded continental upper crust across various sections of previously stretched crust. We propose that necking of the Gondwana lithosphere into several continental microblocks with fertile mantle beneath them compartmentalized extension (multiblock model), which favored the onset of early Paleozoic peralkaline and alkaline magmas. The boundaries of microblocks represent zones of inherited crustal weakness that were later reactivated during the late Paleozoic as major accretionary faults related to the amalgamation of Pangea during the Variscan orogeny. Our dynamic model provides an explanation for the unusual spatial relationship between peralkaline and alkaline igneous provinces (usually shallow in the crust) and the occurrence of high-pressure rocks. Our observations suggest that Cordilleran-type orogens subjected to extension after long-lived subduction can develop wide continental platforms that feature multiple continental blocks. In addition, the formation of sequenced high-pressure belts in collisional orogens can be explained as the ultimate consequence of multiple necking events within continental lithosphere during previous collapse of a Cordilleran-type orogen

Dynamic necking in materials with strain induced martensitic transformation

This work investigates the interplay between inertia and strain induced martensitic transformation (SIMT) on necking inception and energy absorption in dynamically stretched cylindrical rods. For that task a linear stability technique, derived within a quasi-1D framework and specifically accounting for SIMT, has been developed. Likewise, finite element simulations have been performed, using a specific constitutive equation to consider SIMT. Stability analysis and numerical simulations demonstrate that, at high strain rates, inertia may take the dominant role in stabilizing the material, on top of the transformation hardening effects. Furthermore, under certain loading conditions the martensitic transformation may penalize either ductility or energy absorption capacity.Ministerio de Ciencia e Innovación de España (Projects DPI/2011-24068 and DPI/2011-23191)Publicad

Regioselective synthesis of elusive 4,9-Dihydro-1H-Carbazoles by gold-catalyzed cycloisomerization of 3-Allenylmethylindoles

A general and efficient synthesis of 4,9-dihydro- 1H-carbazoles from 3-allenylmethylindoles is reported. The process, catalyzed by a cationic gold(I) complex, involves a formal C2−H bond activation of the indole unit by reaction with the allene. The nature of the substituents at the allylic and terminal positions of the allene moiety has a crucial effect on the regioselectivity of the cyclization, which is also influenced by the catalyst and the solvent employed. Moreover, some evidence of the contribution of different reaction routes is provided, which led us to propose a plausible multipathway mechanism consistent with all of the results described.MICINN and FEDER (CTQ2010-15358 and CTQ2009-09949/BQU) for financial support. E.A. thanks MEC for an FPU predoctoral fellowship. P.G.-G. and M.A.F.-R. thank MICINN for "Juan de la Cierva" and "Ramon y Cajal" contractsThis document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of organic chemistry, copyright © American Chemical Society after peer review and technical editing by the publisher

1,3-Dien-5-ynes: Versatile Building Blocks for the Synthesis of Carbo- and Heterocycles

1,3-Dien-5-ynes have been extensively used as starting materials for the synthesis of a wide number of different carbo- and heterocycles. The aim of this review is to give an overview of their utility in organic synthesis, highlighting the variety of compounds that can be directly accessed from single reactions over these systems. Thus, cycloaromatization processes are initially commented, followed by reactions directed toward the syntheses of five-membered rings, other carbocycles and, finally, heterocycles. The diverse methodologies that have been developed for the synthesis of each of these types of compounds from 1,3-dien-5-ynes are presented, emphasizing the influence of the reaction conditions and the use of additional reagents in the outcome of the transformations.Ministerio de Economía y Competitividad (MINECO) and FEDER (CTQ2013-41336-P, CTQ2013- 48937-C2-1-P, and CTQ2014-52488-R), Universidad de Alcalá (CCG2015/EXP-003) and Junta de Castilla y León (BU237U13

Approaches to the Synthesis of 2,3-Dihaloanilines. Useful Precursors of 4-Functionalized-1H-indoles§

2,3-Dihaloanilines have been proved as useful starting materials for synthesizing 4-halo-1H-indoles. Subsequent or in situ functionalization of the prepared haloindoles allows the access to a wide variety of 2,4- or 2,3,4-regioselectively functionalized indoles in good overall yields. As no efficient synthetic routes to 2,3-dihaloanilines have been described in the literature, different approaches to the preparation of these 1,2,3-functionalized aromatic precursors are now presented. The most general one involves a Smiles rearrangement from the corresponding 2,3-dihalophenols and allows the preparation of 2,3-dihaloanilides in a straightforward and synthetically useful manner.Ministerio de Ciencia e Innovacion (MICINN) and FEDER (CTQ2010-15358) and Junta de Castilla y Leon (BU021A09 and GR-172) for financial support. V.G. thanks Ministerio de Educacion y Ciencia for a MEC-FPU predoctoral fellowship. P.G.-G. and M.A.F.-R. thank MICINN for "Juan de la Cierva" and "Ramon y Cajal" contracts.This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of organic chemistry, copyright © American Chemical Society after peer review and technical editing by the publisher

Brønsted acid−catalyzed synthesis of tetrasubstituted allenes and polysubstituted 2H-chromenes from tertiary propargylic alcohols

A practical and environmentally benign Brønsted acid−catalyzed protocol for the preparation of all-carbon tetrasubstituted allenes, consisting in the direct SNˈ addition of tri- or dimethoxy arenes or allyltrimethylsilane to tertiary propargylic alcohols, has been developed. In addition, a straightforward synthesis of densely substituted 2H-chromenes by metal-free tandem allenylation/heterocyclization reaction of methoxyphenols and tertiary alkynols is presented.Junta de Castilla y León and FEDER (BU291P18) and Ministerio de Economía y Competitividad (MINECO) and FEDER (CTQ2016-75023-C2-1-P

Estrategia medioambiental de la empresa exportadora gallega: ventajas e inconvenientes percibidos

La importancia que gran parte de la población mundial concede a la conservación del medio ambiente supone un nuevo reto para la empresa. Por otra parte, en un mundo globalizado como el actual resulta evidente la importancia que poseen las empresas exportadoras como motor de crecimiento de las economías de los diferentes países del mundo. Con este punto de partida, el objetivo que se persigue en el presente trabajo consiste en evaluar las percepciones de las empresas exportadoras de Galicia en torno a las ventajas e inconvenientes derivados de la implantación de una estrategia medioambiental.Nowadays, most of the population gives a lot of importance to environment conservation, which is a new challenge for the firms. On the other hand, in a world with increasing globalization, the export firms are important to the economic growth of the countries. With this starting point, the objective of this work is to evaluate the perceptions of the Galician export firm about the advantages and disadvantages of the implantation of an environmental strategy

Straightforward Synthesis of Dihydrobenzo[a]fluorenes through Au(I)-Catalyzed Formal [3 + 3] Cycloadditions

Dihydrobenzo[a]fluorene derivatives have been prepared by a formal intramolecular [3 + 3] cycloaddition of o-alkynylstyrenes bearing a secondary alkyl group at the β-position of the styrene moiety. The process, catalyzed by a cationic gold(I) complex, involves a 1,2-hydride migration as the key step. 6,11-Dihydro-5H-benzo[a]fluorenes could be obtained from the initially generated 6,6a-dihydro-5H-benzo[a]fluorenes by subsequent heating of the reaction mixture under gold(I) or Brønsted acid catalysis or directly by conducting the reactions at high temperatureMICINN and FEDER (CTQ2010-15358 and CTQ2009-09949/BQU) and Junta de Castilla y Leon (BU021A09 and GR-172) for financial support. A.M.S. thanks Junta de Castilla y Leon (Consejeria de Educacion) and Fondo Social Europeo for a PIRTU contract. M.A.R. thanks MEC for a "Young Foreign Researchers" contract (SB2009-0186). P.G.-G. and M.A.F.-R. thank MICINN for "Juan de la Cierva" and "Ramon y Cajal" contractsThis document is the Accepted Manuscript version of a Published Work that appeared in final form in Organic Letters, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://pubs.acs.org/page/policy/articlesonrequest/index.htm