The dearomatization of 3‐nitroindoles through a chiral‐phosphine‐mediated 3+2 annulation reaction is described. This method makes use of readily available 3‐nitroindoles as an aromatic feedstock and ...rapidly delivers a wide range of cyclopentaindoline alkaloid scaffolds in a highly enantioselective manner. Notably, phosphine‐triggered cyclization has not been utilized previously in a dearomatization process.
A disruptive influence: Variously substituted 3‐nitroindoles underwent dearomatization in a phosphine‐catalyzed asymmetric 3+2 annulation reaction with allenoates (see scheme). This method makes use of 3‐nitroindoles as a readily available aromatic feedstock and provides access to a wide range of cyclopentaindolines in a highly enantioselective manner.
Super-heptazethrene Zeng, Wangdong; Sun, Zhe; Herng, Tun Seng ...
Angewandte Chemie (International ed.),
July 18, 2016, Letnik:
55, Številka:
30
Journal Article
Recenzirano
The challenging synthesis of a laterally extended heptazethrene molecule, the super‐heptazethrene derivative SHZ‐CF3, is reported. This molecule was prepared using a strategy involving a multiple ...selective intramolecular Friedel–Crafts alkylation followed by oxidative dehydrogenation. Compound SHZ‐CF3 exhibits an open‐shell singlet diradical ground state with a much larger diradical character compared with the heptazethrene derivatives. An intermediate dibenzo‐terrylene SHZ‐2H was also obtained during the synthesis. This study provides a new synthetic method to access large‐size quinoidal polycyclic hydrocarbons with unique physical properties.
Expanding horizons: The complex polycyclic hydrocarbon super‐heptazethrene was synthesized using a strategy involving a selective multiple intramolecular Friedel–Crafts alkylation followed by oxidative dehydrogenation. Super‐heptazethrene displayed a much larger diradical character (y0) than heptazethrene.
A quantitative understanding of the electromagnetic response of materials is essential for the precise engineering of maximal, versatile, and controllable light-matter interactions. Material ...surfaces, in particular, are prominent platforms for enhancing electromagnetic interactions and for tailoring chemical processes. However, at the deep nanoscale, the electromagnetic response of electron systems is significantly impacted by quantum surface-response at material interfaces, which is challenging to probe using standard optical techniques. Here, we show how ultraconfined acoustic graphene plasmons in graphene-dielectric-metal structures can be used to probe the quantum surface-response functions of nearby metals, here encoded through the so-called Feibelman d-parameters. Based on our theoretical formalism, we introduce a concrete proposal for experimentally inferring the low-frequency quantum response of metals from quantum shifts of the acoustic graphene plasmons dispersion, and demonstrate that the high field confinement of acoustic graphene plasmons can resolve intrinsically quantum mechanical electronic length-scales with subnanometer resolution. Our findings reveal a promising scheme to probe the quantum response of metals, and further suggest the utilization of acoustic graphene plasmons as plasmon rulers with ångström-scale accuracy.
Historically, the field of plasmonics has been relying on the framework of classical electrodynamics, with the local-response approximation of material response being applied even when dealing with ...nanoscale metallic structures. However, when the confinement of electromagnetic radiation approaches atomic scales, mesoscopic effects are anticipated to become observable, e.g., those associated with the nonlocal electrodynamic surface response of the electron gas. Here, we investigate nonlocal effects in propagating gap surface plasmon modes in ultrathin metal-dielectric-metal planar waveguides, exploiting monocrystalline gold flakes separated by atomic-layer-deposited aluminum oxide. We use scanning near-field optical microscopy to directly access the near-field of such confined gap plasmon modes and measure their dispersion relation via their complex-valued propagation constants. We compare our experimental findings with the predictions of the generalized nonlocal optical response theory to unveil signatures of nonlocal damping, which becomes appreciable for few-nanometer-sized dielectric gaps.
Detailed radiation analysis of instruments flown in space is critical to ensure mission safety, often requiring the use of state-of-the-art particle transport simulation tools. Geant4 is one of the ...most powerful toolkits to simulate the interaction and the passage of particles through matter, but it is not prepared to receive Standard for The Exchange of Product data (STEP) files, the most versatile Computer-Aided Design (CAD) format, as input, requiring previous conversion to other CAD formats. This may lead to loss of detail and under or overestimation of the quantities under study, especially when the instruments have complex shapes, and/or a large number of volumes. Though several solutions have been proposed to import complex geometries from STEP files into Geant4, so far, only commercial options are available. In this paper we present a new tool, GUIMesh, that embeds FreeCAD libraries, an open-source CAD editor, to tessellate volumes, and convert them to Geometry Description Markup Language (GDML), a Geant4 readable format, in a straightforward way. Several degrees of freedom are given to the user regarding mesh precision and choice of material. Different geometries were tested for material definition, geometry and navigation errors, and the method used was successfully validated.
Program Title: GUIMesh
Program Files doi: http://dx.doi.org/10.17632/c3c9xbspzp.1
Licensing provisions: GNU General Public License 3 (GPLv3)
Programming language: Python
Nature of problem: No open-source software allows to import STEP geometries intro Geant4, one of the most powerful toolkits to simulate radiation interaction with matter. Since CAD software is extensively used in the design of particle and radiation detection instruments, it is highly desirable for physicists that STEP geometries can be imported to Geant4 with little effort instead of having to code structures made of a very large number of solid volumes which are difficult to accurately reproduce with Geant4 C++ classes.
Solution method: STEP geometries are converted to tessellated volumes (with some margin of error) using FreeCAD libraries. A Python script then writes GDML files based on the results allowing users to import these geometries with Geant4. A graphical user interface provides several options to the user, including material assignment and mesh precision setting for each volume.
Substituted cyclohexylamines are becoming increasingly important in drug discovery. Asymmetric Heck insertion/amination of nonconjugated cyclodienes proceeds to give 5‐aryl cyclohexenylamines with ...good enantioselectivity and exclusive trans configurations. Primary and secondary anilines, indoline, and benzylamines are suitable amines. The weakly donating diphosphite Kelliphite forms a deep unsymmetrical pocket, which is essential for stereoselective anti attack of amines.
Deep pockets: Heck arylation of nonconjugated dienes under palladium catalysis produces π‐allyl complexes, which can be trapped by various amines to give substituted cyclohexenylamines with good enantioselectivity and exclusively trans configuration. The weakly donating diphosphate ligand Kelliphite forms a deep unsymmetrical pocket, which is essential for stereoselective anti attack of amines.
Monazite is a common accessory phase in felsic granulite ribbon mylonites exposed in the Upper Deck domain of the Athabasca granulite terrane, western Canadian Shield. Field relationships, bulk rock ...geochemistry and phase equilibria modelling in the Na2O–CaO–K2O–FeO–MgO–Al2O3–SiO2–H2O–TiO2–Fe2O3 system are consistent with the garnet‐rich rocks representing the residual products of ultrahigh temperature melting of biotite‐bearing paragneisses driven by intraplating of mafic magma in continental lower crust. The c. 2.64–2.61 Ga Y‐rich resorbed monazite cores included in garnet are interpreted as relicts of detrital grains deposited on the Earth's surface after c. 2.61 Ga. Yttrium‐poor monazite domains in garnet are depleted in Sm and Gd and linked to fluid‐absent melting of biotite + plagioclase + quartz ± sillimanite during a prograde loading path from ≤0.8 to ≥1.4 GPa. The c. 2.61–2.55 Ga Y‐depleted, Th‐rich monazite domains crystallized in the presence of garnet + ternary feldspar ± orthopyroxene + peraluminous melt. The c. 2.58–2.52 Ga monazite rims depleted in Th + Ca and enriched in Eu are linked to localized melt extraction synchronous with growth of high‐pressure (HP) grossular‐rich garnet at the expense of plagioclase during crustal thickening, culminating at >950 °C. Re‐heating and dextral transpressive lower crustal reactivation at c. 1.9 Ga resulted in syn‐kinematic growth of (La + Ce)‐enriched monazite and a second generation of garnet, concurrent with recrystallization of feldspar and orthopyroxene at 1.0–1.2 GPa and 600–700 °C. Monazite grains in this study are marked by positive Eu‐anomalies relative to chondrite. A direct link is implied between Y, Sm, Eu and Gd in monazite and two major phases in continental lower crust: garnet and plagioclase. Positive Eu‐anomalies in lower crustal monazite associated with modally abundant garnet appear to be directly related to Eu‐enrichment and depletions of Y, Sm and Gd that are consequences of garnet growth and plagioclase breakdown during HP melting of peraluminous bulk compositions.
Introduction In December 2019, an outbreak of the novel coronavirus, the coronavirus disease 2019 (COVID-19) probably occurred in Wuhan, China. By March 2020, the World Health Organization (WHO) had ...declared a pandemic. Containment measures such as social distancing and hand hygiene were recommended. In this study, we start from the hypothesis that engaging with containment measures in a pandemic situation should be more comfortable for some people than for other people. Thus, individual differences should be associated with engagement with containment measures. Objective To investigate to what extent two personality traits, extroversion and conscientiousness, are associated with engagement with two containment measures (social distancing and handwashing). Methods The sample consisted of 715 Brazilian adults aged 18-78 years, who answered the Big Five Inventory 2 Short (BFI-2-S) and factors from the Dimensional Clinical Personality Inventory 2 (IDCP-2). Results Higher scores for extroversion were associated with lower means for social distancing (p < 0.001) and higher scores for conscientiousness were associated with higher means for social distancing and handwashing (p < 0.05). Conclusion The findings indicate the importance of acknowledging extroversion and conscientiousness traits as relevant to people's engagement with the measures recommended for COVID-19 containment.
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