David B

Chemoselective Bromination of Dienoates

Chemoselective Bromination of Dienoates

One isomer or another! Chemo‐ and stereoselectivity of dienoates bromination depends strongly on the substituent nature in starting ester and reaction conditions.

A variety of tetra‐, di‐ and monobromo derivatives of dienoates were prepared from parent polyunsaturated esters under mild conditions. According to proposed protocol the target bromoesters were easily obtained as a rule in good yields and high selectivity.

Wiley: European Journal of Organic Chemistry: Table of Contents
Authors: Valentina A. Kobelevskaya, Alexander V. Popov, Sergey V. Zinchenko, Alexander Yu. Rulev
doi.org/10.1002/ejoc.202000893

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Divergent Synthesis of Monosubstituted and Unsymmetrical 3,6‐Disubstituted Tetrazines from Carboxylic Ester Precursors

Divergent Synthesis of Monosubstituted and Unsymmetrical 3,6‐Disubstituted Tetrazines from Carboxylic Ester Precursors

Divergent tetrazine synthesis : Described is a new strategy for the one‐pot synthesis of 3‐thiomethyltetrazines from carboxylic ester precursors, which provides a platform for the synthesis of unsymmetrical tetrazines through Pd‐catalyzed cross‐coupling and the first catalytic thioether reduction to access monosubstituted tetrazines.

Abstract

Since tetrazines are important tools to the field of bioorthogonal chemistry, there is a need for new approaches to synthesize unsymmetrical and 3‐monosubstituted tetrazines. Described here is a general, one‐pot method for converting (3‐methyloxetan‐3‐yl)methyl carboxylic esters into 3‐thiomethyltetrazines. These versatile intermediates were applied to the synthesis of unsymmetrical tetrazines through Pd‐catalyzed cross‐coupling and in the first catalytic thioether reduction to access monosubstituted tetrazines. This method enables the development of new tetrazine compounds possessing a favorable combination of kinetics, small size, and hydrophilicity. It was applied to a broad range of aliphatic and aromatic ester precursors and to the synthesis of heterocycles including BODIPY fluorophores and biotin. In addition, a series of tetrazine probes for monoacylglycerol lipase (MAGL) were synthesized and the most reactive one was applied to the labeling of endogenous MAGL in live cells.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Yixin Xie, Yinzhi Fang, Zhen Huang, Amanda M. Tallon, Christopher W. am Ende, Joseph M. Fox
doi.org/10.1002/anie.202005569

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Halogen Bonding Between Anions: Association of Anion Radicals of Tetraiodo‐p‐benzoquinone with Iodide Anions

Halogen Bonding Between Anions: Association of Anion Radicals of Tetraiodo‐p‐benzoquinone with Iodide Anions

Unconventionally attractive : Counter‐intuitive halogen bonding between tetraiodo‐p‐benzoquinone anion radicals I4Q and iodide anions was identified in crystals of (Et4N)2I⋅I4Q. Computational analysis related this seemingly antielectrostatic anion–anion bonding to the polarization of I4Q moieties by the iodide anions, leading to the appearance of an area of positive charge on the surface of the iodine substituents in p‐benzoquinone.

Abstract

Halogen bonding between two negatively charged species, tetraiodo‐p‐benzoquinone anion radicals (I4Q−.) and iodide anions, was observed and characterized for the first time. X‐ray structural and EPR/UV–Vis spectral studies revealed that the anion–anion bonding led to the formation of crystals comprising 2D layers of I4Q−. anion radicals linked by iodides and separated by Et4N+ counter‐ions. Computational analysis suggested that the seemingly antielectrostatic halogen bonds in these systems were formed via a combination of several factors. First, an attenuation of the interionic repulsion by the solvent facilitated close approach of the anions leading to their mutual polarization. This resulted in the appearance of positively charged areas (σ‐holes) on the surface of the iodine substituents in I4Q−. responsible for the attractive interaction. Finally, the solid‐state associations were also stabilized by multicenter (4:4) halogen bonding between I4Q−. and iodide.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Tristan Maxson, Almaz S. Jalilov, Matthias Zeller, Sergiy V. Rosokha
doi.org/10.1002/anie.202004384

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Homo‐ and Hetero‐dinuclear Arene‐Linked Osmium(II) and Ruthenium(II) Organometallics: Probing the Impact of Metal Variation on Reactivity and Biological Activity

Homo‐ and Hetero‐dinuclear Arene‐Linked Osmium(II) and Ruthenium(II) Organometallics: Probing the Impact of Metal Variation on Reactivity and Biological Activity

Dinuclear metallodrugs : A family of homo‐dinuclear and hetero‐dinuclear arene‐linked OsII‐OsII and OsII‐RuII organometallic complexes has been developed, and a comparative study with the isostructural RuII–RuII analogue, a chromatin‐modifying agent, is described.

Abstract

Dinuclear metallodrugs offer much potential in the development of novel anticancer chemotherapeutics as a result of the distinct interactions possible with bio‐macromolecular targets and the unique biological activity that can result. Herein, we describe the development of isostructural homo‐dinuclear OsII–OsII and hetero‐dinuclear OsII–RuII organometallic complexes formed from linking the arene ligands of [M(η6‐arene)(C2O4)(PTA)] units (M=Os/Ru; PTA=1,3,5‐triaza‐7‐phosphaadamantane). Using these complexes together with the known RuII–RuII analogue, a chromatin‐modifying agent, we probed the impact of varying the metal ions on the structure, reactivity and biological activity of these complexes. The complexes were structurally characterised by X‐ray diffraction experiments, their stability and reactivity were examined by using 1H and 31P NMR spectroscopy, and their biological activity was assessed, alongside that of mononuclear analogues, through MTT assays and cell‐cycle analysis (HT‐29 cell line). The results revealed high antiproliferative activity in each case, with cell‐cycle profiles of the dinuclear complexes found to be similar to that for untreated cells, and similar but distinct profiles for the mononuclear complexes. These results indicate these complexes impact on cell viability predominantly through a non‐DNA‐damaging mechanism of action. The new OsII–OsII and OsII–RuII complexes reported here are further examples of a family of compounds operating via mechanisms of action atypical of the majority of metallodrugs, and which have potential as tools in chromatin research.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Christopher S. Wilson, Timothy J. Prior, Jordon Sandland, Huguette Savoie, Ross W. Boyle, Benjamin S. Murray
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202002052

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Four‐Component Borocarbonylation of Vinylarenes Enabled by Cooperative Cu/Pd Catalysis: Access to β‐Boryl Ketones and β‐Boryl Vinyl Esters

Four‐Component Borocarbonylation of Vinylarenes Enabled by Cooperative Cu/Pd Catalysis: Access to β‐Boryl Ketones and β‐Boryl Vinyl Esters

Joint catalysis : The cooperative Cu/Pd‐catalyzed four‐component borocarbonylation of vinylarenes, aryl halides/triflates, B2Pin2, and CO generates β‐boryl ketones and β‐boryl vinyl esters in good to high yields. A rational mechanism was proposed for the synthesis of β‐boryl vinyl esters, which involves an acyl‐copper intermediate in the Cu cycle.

Abstract

We report here a general four‐component synthetic procedure for the preparation of β‐boryl ketones and β‐boryl vinyl esters. Joint catalyzed by palladium and copper catalysts, borocarbonylative reaction between vinylarenes, aryl halides/triflates, B2Pin2, and carbon monoxide proceed successfully. A variety of synthetically useful β‐boryl ketones were synthesized in good to high yields by using aryl iodides as the substrates. It is noteworthy that when aryl triflates were applied as the starting materials, β‐boryl vinyl esters were synthesized in a similar manner and with broad functional group tolerance. A rational mechanism for this reaction was also proposed.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Yang Yuan, Fu‐Peng Wu, Jian‐Xing Xu, Xiao‐Feng Wu
doi.org/10.1002/anie.202006427

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Atomic Layer Deposition of Cobalt Phosphide for Efficient Water Splitting

Atomic Layer Deposition of Cobalt Phosphide for Efficient Water Splitting

Cobalt phosphide is prepared by atomic layer deposition for the first time. The optimized recipe employs an extra H2 plasma step to remove excess phosphorus. The as‐deposited Co‐P films demonstrate significantly higher activities towards electrochemical and photoelectrochemical hydrogen evolution reaction than that prepared by a traditional method.

Abstract

Transition‐metal phosphides (TMP) prepared by atomic layer deposition (ALD) are reported for the first time. Ultrathin Co‐P films were deposited by using PH3 plasma as the phosphorus source and an extra H2 plasma step to remove excess P in the growing films. The optimized ALD process proceeded by self‐limited layer‐by‐layer growth, and the deposited Co‐P films were highly pure and smooth. The Co‐P films deposited via ALD exhibited better electrochemical and photoelectrochemical hydrogen evolution reaction (HER) activities than similar Co‐P films prepared by the traditional post‐phosphorization method. Moreover, the deposition of ultrathin Co‐P films on periodic trenches was demonstrated, which highlights the broad and promising potential application of this ALD process for a conformal coating of TMP films on complex three‐dimensional (3D) architectures.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Haojie Zhang, Dirk J. Hagen, Xiaopeng Li, Andreas Graff, Frank Heyroth, Bodo Fuhrmann, Ilya Kostanovskiy, Stefan L. Schweizer, Francesco Caddeo, A. Wouter Maijenburg, Stuart Parkin, Ralf B. Wehrspohn
doi.org/10.1002/anie.202002280

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Electron Microscopy Studies of Local Structural Modulations in Zeolite Crystals

Electron Microscopy Studies of Local Structural Modulations in Zeolite Crystals

Local structure modulations deviating from ideal framework‐type structures are important fine‐structural features within zeolite frameworks. By using (S)TEM with diffraction and imaging approaches, point, column and planar modulations can be observed in both reciprocal and real space.

Abstract

Zeolites are widely used in catalysis, gas separation, ion exchange, etc. due to their superior physicochemical properties, which are closely related to specific features of their framework structures. Although more than two hundred different framework types have been recognized, it is of great interest to explore from a crystallographic perspective, the atomic positions, surface terminations, pore connectivity and structural defects that deviate from the ideal framework structures, namely local structural modulation. In this article, we review different types of local modulations in zeolite frameworks using various techniques, especially electron microscopy (EM). The most recent advances in resolving structural information at the atomic level with aberration corrected EM are also presented, commencing a new era of gaining atomic structural information, not only for all tetrahedral atoms including point vacancies in framework but also for extra‐framework cations and surface terminations.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Qing Zhang, Alvaro Mayoral, Junyan Li, Juanfang Ruan, Viveka Alfredsson, Yanhang Ma, Jihong Yu, Osamu Terasaki
doi.org/10.1002/anie.202007490

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Self‐Sorting Supramolecular Polymerization: Helical and Lamellar Aggregates of Tetra‐Bay‐Acyloxy Perylene Bisimide

Self‐Sorting Supramolecular Polymerization: Helical and Lamellar Aggregates of Tetra‐Bay‐Acyloxy Perylene Bisimide

Cool down : Depending on the cooling rate, a monomeric perylene bisimide equipped with four acyloxy bay substituents self‐assembles into two distinct polymorphs that exhibit distinctive optical properties and packing arrangements. The interchromophoric arrangement was elucidated in the liquid‐crystalline state, demonstrating the effect of homo‐ versus heterochiral self‐sorting, directing self‐assembly into one‐ or two‐dimensional structures, respectively.

Abstract

A new perylene bisimide (PBI), with a fluorescence quantum yield up to unity, self‐assembles into two polymorphic supramolecular polymers. This PBI bears four solubilizing acyloxy substituents at the bay positions and is unsubstituted at the imide position, thereby allowing hydrogen‐bond‐directed self‐assembly in nonpolar solvents. The formation of the polymorphs is controlled by the cooling rate of hot monomer solutions. They show distinctive absorption profiles and morphologies and can be isolated in different polymorphic liquid‐crystalline states. The interchromophoric arrangement causing the spectral features was elucidated, revealing the formation of columnar and lamellar phases, which are formed by either homo‐ or heterochiral self‐assembly, respectively, of the atropoenantiomeric PBIs. Kinetic studies reveal a narcissistic self‐sorting process upon fast cooling, and that the transformation into the heterochiral (racemic) sheetlike self‐assemblies proceeds by dissociation via the monomeric state.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Markus Hecht, Pawaret Leowanawat, Tabea Gerlach, Vladimir Stepanenko, Matthias Stolte, Matthias Lehmann, Frank Würthner
doi.org/10.1002/anie.202006744

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Tetrazine Carbon Nanotubes for Pretargeted In Vivo “Click‐to‐Release” Bioorthogonal Tumour Imaging

Tetrazine Carbon Nanotubes for Pretargeted In Vivo “Click‐to‐Release” Bioorthogonal Tumour Imaging

Pretarget then activate : Functionalization of single‐walled carbon nanotubes (SWCNTs) with tetrazines led to a stable and biocompatible material that undergoes a rapid inverse‐electron‐demand Diels–Alder reaction with trans‐cyclooctene caged molecules. This approach enables bioorthogonal activation of responsive drugs or probes in solid tumours in a strictly controlled manner.

Abstract

The bioorthogonal inverse‐electron‐demand Diels–Alder (IEDDA) cleavage reaction between tetrazine and trans‐cyclooctene (TCO) is a powerful way to control the release of bioactive agents and imaging probes. In this study, a pretargeted activation strategy using single‐walled carbon nanotubes (SWCNTs) that bear tetrazines (TZ@SWCNTs) and a TCO‐caged molecule was used to deliver active effector molecules. To optimize a turn‐on signal by using in vivo fluorescence imaging, we developed a new fluorogenic near‐infrared probe that can be activated by bioorthogonal chemistry and image tumours in mice by caging hemicyanine with TCO (tHCA). With our pretargeting strategy, we have shown selective doxorubicin prodrug activation and instantaneous fluorescence imaging in living cells. By combining a tHCA probe and a pretargeted bioorthogonal approach, real‐time, non‐invasive tumour visualization with a high target‐to‐background ratio was achieved in a xenograft mice tumour model. The combined advantages of enhanced stability, kinetics and biocompatibility, and the superior pharmacokinetics of tetrazine‐functionalised SWCNTs could allow application of targeted bioorthogonal decaging approaches with minimal off‐site activation of fluorophore/drug.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: He Li, João Conde, Ana Guerreiro, Gonçalo J. L. Bernardes
doi.org/10.1002/anie.202008012

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Proving and Probing the Presence of the Elusive C−H⋅⋅⋅O Hydrogen Bond in Liquid Solutions at Room Temperature

Proving and Probing the Presence of the Elusive C−H⋅⋅⋅O Hydrogen Bond in Liquid Solutions at Room Temperature

Weak bonds : Evidence of the presence of weak hydrogen bonds between the highly polarized C−H of chloroform and a carbonyl oxygen atom at room temperature was obtained using ultrafast two‐dimensional infrared spectroscopy (2DIR). The signature of the making and breaking of these weak hydrogen bonds, as well as its approximate 4 ps time scale was derived from the crosspeak growth in the 2DIR spectrum.

Abstract

Hydrogen bonds (H bonds) play a major role in defining the structure and properties of many substances, as well as phenomena and processes. Traditional H bonds are ubiquitous in nature, yet the demonstration of weak H bonds that occur between a highly polarized C−H group and an electron‐rich oxygen atom, has proven elusive. Detailed here are linear and nonlinear IR spectroscopy experiments that reveal the presence of H bonds between the chloroform C−H group and an amide carbonyl oxygen atom in solution at room temperature. Evidence is provided for an amide solvation shell featuring two clearly distinguishable chloroform arrangements that undergo chemical exchange with a time scale of about 2 ps. Furthermore, the enthalpy of breaking the hydrogen bond is found to be 6–20 kJ mol−1. Ab‐initio computations support the findings of two distinct solvation shells formed by three chloroform molecules, where one thermally undergoes hydrogen‐bond making and breaking.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Susith R. Galle Kankanamge, Jianbo Ma, Robert T. Mackin, Fedra M. Leonik, Carol M. Taylor, Igor V. Rubtsov, Daniel G. Kuroda
doi.org/10.1002/anie.202006210

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A Robust Porous Quinoline Cage: Transformation of a [4+6] Salicylimine Cage by Povarov Cyclization

A Robust Porous Quinoline Cage: Transformation of a [4+6] Salicylimine Cage by Povarov Cyclization

Cage to cage : Soluble, porous, and chemically stable quinoline cages are synthesized from salicylimine cages in one post‐synthetic step. The cages show characteristic acidochromic behavior in bulk and solution, and as thin‐films.

Abstract

Porous shape‐persistent organic cages have become the object of interest in recent years because they are soluble and thus processable from solution. A variety of cages can be achieved by applying dynamic covalent chemistry (DCC), but they are less chemically stable. Here the transformation of a salicylimine cage into a quinoline cage by a twelve‐fold Povarov reaction as the key step is described. Besides the chemical stability of the cage over a broad pH regime, it shows a unique absorption and emission depending on acid concentration. Furthermore, thin films for the vapor detection of acids were investigated, showing color switches from pale‐yellow to red, and characteristic emission profiles.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Pierre‐Emmanuel Alexandre, Wen‐Shan Zhang, Frank Rominger, Sven M. Elbert, Rasmus R. Schröder, Michael Mastalerz
doi.org/10.1002/anie.202007048

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BIMP‐Catalyzed 1,3‐Prototropic Shift for the Highly Enantioselective Synthesis of Conjugated Cyclohexenones

BIMP‐Catalyzed 1,3‐Prototropic Shift for the Highly Enantioselective Synthesis of Conjugated Cyclohexenones

Get a shift on : An enantioselective bifunctional iminophosphorane (BIMP)‐catalysed 1,3‐prototropic shift of structurally diverse β,γ‐unsaturated cyclohexenones is reported. The reaction is high yielding (up to 99 %) in a short time span and proceeds with a high level of selectivity (up to 99 % ee ) on a wide range of substrates. To complement the experimental data, in‐depth computational studies were undertaken, including multivariate linear regression of TS energy.

Abstract

A bifunctional iminophosphorane (BIMP)‐catalysed enantioselective synthesis of α,β‐unsaturated cyclohexenones through a facially selective 1,3‐prototropic shift of β,γ‐unsaturated prochiral isomers, under mild reaction conditions and in short reaction times, on a range of structurally diverse substrates, is reported. α,β‐Unsaturated cyclohexenone products primed for downstream derivatisation were obtained in high yields (up to 99 %) and consistently high enantioselectivity (up to 99 % ee ). Computational studies into the reaction mechanism and origins of enantioselectivity, including multivariate linear regression of TS energy, were carried out and the obtained data were found to be in good agreement with experimental findings.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Jonathan C. Golec, Eve M. Carter, John W. Ward, William G. Whittingham, Luis Simón, Robert S. Paton, Darren J. Dixon
doi.org/10.1002/anie.202006202

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Synthesis of 1,3‐Bis‐(boryl)alkanes through Boronic Ester Induced Consecutive Double 1,2‐Migration

Synthesis of 1,3‐Bis‐(boryl)alkanes through Boronic Ester Induced Consecutive Double 1,2‐Migration

Two is better than one : Commercially available ICH2Bpin reacts with readily prepared vinylboron ate complexes under practical conditions to valuable 1,3‐bis‐(boryl)alkanes. The cascade proceeds through two subsequent 1,2‐metallate rearrangements of boronate complexes, with the second boronate being form in the initial 1,2‐migration step.

Abstract

A general and efficient approach for the preparation of 1,3‐bis‐(boryl)alkanes is introduced. It is shown that readily generated vinylboron ate complexes react with commercially available ICH2Bpin to valuable 1,3‐bis‐(boryl)alkanes. The introduced transformation, which is experimentally easy to conduct, shows broad substrate scope and high functional‐group tolerance. Mechanistic studies reveal that the reaction does not proceed via radical intermediates. Instead, an unprecedented boronic ester induced sequential bis‐1,2‐migration cascade is suggested.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Cai You, Armido Studer
doi.org/10.1002/anie.202007541

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The Sphingosine and Acyl Chains of Ceramide [NS] Show Very Different Structure and Dynamics That Challenge Our Understanding of the Skin Barrier

The Sphingosine and Acyl Chains of Ceramide [NS] Show Very Different Structure and Dynamics That Challenge Our Understanding of the Skin Barrier

Dynamic chains in a rigid matrix : While the sphingosine chains of ceramide molecules in the outermost human skin layer were originally assumed to be fully rigid, spectroscopic data reveals that they display a complex dynamic behavior. These new insights will help fine‐tune the molecular model of the skin lipid barrier.

Abstract

The lipid phase of the uppermost human skin layer is thought to comprise highly rigid lipids in an orthorhombic phase state to protect the body against the environment. By synthesizing sphingosine‐d28 deuterated N‐lignoceroyl‐d ‐erythro‐sphingosine (ceramide [NS]), we compare the structure and dynamics of both chains of that lipid in biologically relevant mixtures using X‐ray diffraction, 2H NMR analysis, and infrared spectroscopy. Our results reveal a substantial fraction of sphingosine chains in a fluid and dynamic phase state at physiological temperature. These findings prompt revision of our current understanding of the skin lipid barrier, where an extended ceramide [NS] conformation is preferred and a possible domain structure is proposed. Mobile lipid chains may be crucial for skin elasticity and the translocation of physiologically important molecules.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Oskar Engberg, Andrej Kováčik, Petra Pullmannová, Martin Juhaščik, Lukáš Opálka, Daniel Huster, Kateřina Vávrová
doi.org/10.1002/anie.202003375

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Self‐Assembly of Perovskite CsPbBr3 Quantum Dots Driven by a Photo‐Induced Alkynyl Homocoupling Reaction

Self‐Assembly of Perovskite CsPbBr3 Quantum Dots Driven by a Photo‐Induced Alkynyl Homocoupling Reaction

Under UV irradiation, the homocoupling reaction between two alkynyl groups of a surfactant molecule, 1‐alkynyl acid, is effectively catalyzed by CsBr, the byproduct formed during CsPbBr3 perovskite quantum‐dot (PQD) synthesis. This further drives the self‐assembly of PQDs and leads to the formation of 3D perovskite supercrystals.

Abstract

Herein, we report the facile growth of three‐dimensional CsPbBr3 perovskite supercrystals (PSCs) self‐assembled from individual CsPbBr3 perovskite quantum dots (PQDs). By varying the carbon chain length of a surface‐bound ligand molecule, 1‐alkynyl acid, different morphologies of PSCs were obtained accompanied by an over 1000‐fold photoluminescence improvement compared with that of PQDs. Systematic analyses have shown, for the first time, that under UV irradiation, CsBr, the byproduct formed during PQDs synthesis, could effectively catalyze the homocoupling reaction between two alkynyl groups, which further worked as a driving force to push forward the self‐assembly of PQDs.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Hongbo Li, Xiangdong Liu, Qifei Ying, Chao Wang, Wei Jia, Xing Xing, Lisha Yin, Zhenda Lu, Kun Zhang, Yue Pan, Zhan Shi, Ling Huang, Dianzeng Jia
doi.org/10.1002/anie.202004947

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Synthesis and Post‐Synthesis Transformation of Germanosilicate Zeolites

Synthesis and Post‐Synthesis Transformation of Germanosilicate Zeolites

Recent advances in synthesis of germanosilicate zeolites and their post‐synthesis transformations to novel porous materials are reviewed. The structure‐directing effect of Ge allows the synthesis of new zeolite structures with labile Ge−O bonds in aqueous solutions.

Abstract

Zeolites are one of the most important heterogeneous catalysts, with a high number of large‐scale industrial applications. While the synthesis of new zeolites remain rather limited, introduction of germanium has substantially increased our ability to not only direct the synthesis of zeolites but also to convert them into new materials post‐synthetically. The smaller Ge‐O‐Ge angles (vs. Si‐O‐Si) and lability of the Ge−O bonds in aqueous solutions account for this behaviour. This Minireview discusses critical aspects of germanosilicate synthesis and their post‐synthesis transformations to porous materials.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Maksym Opanasenko, Mariya Shamzhy, Yunzheng Wang, Wenfu Yan, Petr Nachtigall, Jiří Čejka
doi.org/10.1002/anie.202005776

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Handling (Nano)Silver as Antimicrobial Agent: Therapeutic Window, Dissolution Dynamics, Detection Methods and Molecular Interactions

Handling (Nano)Silver as Antimicrobial Agent: Therapeutic Window, Dissolution Dynamics, Detection Methods and Molecular Interactions

Friend or foe? Rarely has a biologically active element discussed so controversially been discussed than silver in ionic or nano form. This Review draws together literature from chemistry, materials and environmental sciences, biology and medicine to give insight into the activity and mechanism of silver in biological media, be it in contact with bacteria or cells.

Abstract

Silver is an antimicrobial agent well known since antiquity. With the emergence of multiresistant bacteria, it has come back into the focus of research, and ionic as well as nano‐sized silver have been studied in vitro and in vivo. The results are controversial, silver being discussed as the “silver bullet” or a “wolf in sheep’s clothing”. A thorough search of literature from chemistry, materials and environmental science, biology and medicine led to this Review which summarizes the potential use of silver and its compounds in medicine, ongoing processes of dissolution and the different methods by which this usefulness can be evaluated. It also highlights the therapeutic window of silver, mechanistic interactions of silver and biological media as well as best practices for handling silver in a biomedical environment. This Review reflects the current knowhow and observations, and may thus give hints and guidelines to understand and interpret the observed effects.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Sarah‐Luise Abram, Katharina M. Fromm
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202002143

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N‐Heterocyclic Carbenes Reduce and Functionalize Copper Oxide Surfaces in One Pot

N‐Heterocyclic Carbenes Reduce and Functionalize Copper Oxide Surfaces in One Pot

Monolayers : For the first time, a simultaneous etch‐functionalize protocol has been developed for oxidized copper surfaces using N‐heterocyclic carbenes. These results demonstrate the dual functionality of N‐heterocyclic carbenes when applied to more reactive metal surfaces that are prone to oxidation and offers a new strategy for chemical etching that avoids dangerous reagents. This work also provides an opportunity to replace precious metals, such as gold, with more abundant metals, such as copper, in organic‐on‐metal devices.

Abstract

Benzimidazolium hydrogen carbonate salts have been shown to act as N‐heterocyclic carbene precursors, which can remove oxide from copper oxide surfaces and functionalize the resulting metallic surfaces in a single pot. Both the surfaces and the etching products were fully characterized by spectroscopic methods. Analysis of surfaces before and after NHC treatment by X‐ray photoelectron spectroscopy demonstrates the complete removal of copper(II) oxide. By using 13C‐labelling, we determined that the products of this transformation include a cyclic urea, a ring‐opened formamide and a bis‐carbene copper(I) complex. These results illustrate the potential of NHCs to functionalize a much broader class of metals, including those prone to oxidation, greatly facilitating the preparation of NHC‐based films on metals other than gold.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Alex J. Veinot, Abrar Al‐Rashed, J. Daniel Padmos, Ishwar Singh, Dianne S. Lee, Mina R. Narouz, Paul A. Lummis, Christopher J. Baddeley, Cathleen M. Crudden, J. Hugh Horton
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202002308

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Asymmetric Hydrogenation of Cationic Intermediates for the Synthesis of Chiral N,O‐Acetals

Asymmetric Hydrogenation of Cationic Intermediates for the Synthesis of Chiral N,O‐Acetals

Chiral N , O ‐acetals have been prepared with remarkably high enantioselectivities from both N‐ and O‐acetylsalicylamides by the asymmetric hydrogenation of cationic intermediates under acidic conditions. The catalytic system employed shows high chemoselectivity. Mechanistic studies support the in situ formation of a cationic sp2‐carbon intermediate that was subsequently reduced by an outer‐sphere hydride transfer.

Abstract

For over half a century, transition‐metal‐catalyzed homogeneous hydrogenation has been mainly focused on neutral and readily prepared unsaturated substrates. Although the addition of molecular hydrogen to C=C, C=N, and C=O bonds represents a well‐studied paradigm, the asymmetric hydrogenation of cationic species remains an underdeveloped area. In this study, we were seeking a breakthrough in asymmetric hydrogenation, with cationic intermediates as targets, and thereby anticipating applying this powerful tool to the construction of challenging chiral molecules. Under acidic conditions, both N‐ or O‐acetylsalicylamides underwent cyclization to generate cationic intermediates, which were subsequently reduced by an iridium or rhodium hydride complex. The resulting N ,O‐acetals were synthesized with remarkably high enantioselectivity. This catalytic strategy exhibited high efficiency (turnover number of up to 4400) and high chemoselectivity. Mechanistic studies supported the hypothesis that a cationic intermediate was formed in situ and hydrogenated afterwards. A catalytic cycle has been proposed with hydride transfer from the iridium complex to the cationic sp2 carbon atom being the rate‐determining step. A steric map of the catalyst has been created to illustrate the chiral environment, and a quantitative structure–selectivity relationship analysis showed how enantiomeric induction was achieved in this chemical transformation.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Yongjie Sun, Qingyang Zhao, Heng Wang, Tilong Yang, Jialin Wen, Xumu Zhang
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202002930

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Benzosiloles with Crystallization‐Induced Emission Enhancement of Electrochemiluminescence: Synthesis, Electrochemistry, and Crystallography

Benzosiloles with Crystallization‐Induced Emission Enhancement of Electrochemiluminescence: Synthesis, Electrochemistry, and Crystallography

The photoluminescence and electrochemiluminescence (ECL) of two benzosiloles are significantly enhanced upon their crystallization. The developed ECL system with crystallization‐induced emission enhancement is clearly differentiated from ECL systems with aggregation‐induced emission enhancement, and it is also anticipated to find applications in ECL sensing and optoelectronics (see figure).

Abstract

Crystallization‐induced emission enhancement (CIEE) was demonstrated for the first time for electrochemilunimescence (ECL) with two new benzosiloles. Compared with their solution, the films of the two benzosiloles gave CIEE of 24 and 16 times. The mechanism of the CIEE‐ECL was examined by spooling ECL spectroscopy, X‐ray crystal structure analysis, photoluminescence, and DFT calculations. This CIEE‐ECL system is a complement to the well‐established aggregation‐induced emission enhancement (AIEE) systems. Unique intermolecular interactions are noted in the crystalline chromophore. The first heterogeneous ECL system is established for organic compounds with highly hydrophobic properties.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Liuqing Yang, Donghyun Koo, Jackie Wu, Jonathan M. Wong, Tyler Day, Ruizhong Zhang, Harshana Kolongoda, Kehan Liu, Jian Wang, Zhifeng Ding, Brian L. Pagenkopf
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202002647

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Hydrolysis of Peptide Bonds in Protein Micelles Promoted by a Zirconium(IV)‐Substituted Polyoxometalate as an Artificial Protease

Hydrolysis of Peptide Bonds in Protein Micelles Promoted by a Zirconium(IV)‐Substituted Polyoxometalate as an Artificial Protease

The hydrolysis of hydrophobic and unstructured proteins is difficult due to their poor solubility in aqueous solutions. This study demonstrates the ability of ZrIV‐substituted Keggin polyoxometalate (Et2NH2)10[Zr(α‐PW11O39)2] to promote selective hydrolysis of β‐casein, an intrinsically unstructured protein consisting of 209 amino acids. The amphipathic nature of β‐casein causes it to assemble into large micelles, in which the hydrophilic part of the protein is solvent exposed and able to interact with Zr‐POM that activates peptide bonds towards hydrolysis. More information can be found in the Full Paper by T. N. Parac‐Vogt et al. (DOI: doi.org/10.1002/chem.20200192010.1002/chem.202001920).

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Thomas Quanten, Nada D. Savić, Tatjana N. Parac‐Vogt
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202003297

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Single Peptide Backbone Surrogate Mutations to Regulate Angiotensin GPCR Subtype Selectivity

Single Peptide Backbone Surrogate Mutations to Regulate Angiotensin GPCR Subtype Selectivity

Single peptide backbone surrogate 1,2,3‐triazole mutations can regulate angiotensin GPCR subtype selectivity. [Y]6‐Angiotensin II analogs with amide bonds replaced by 1,4‐disubstituted isosteres illustrated enhanced AT2R/AT1R subtype selectivity and enhanced neurite growth in embryonic mouse cortical cells (E15). Neurite outgrowth (red color) was visualized using an anti‐MAP2 antibody. Nuclei, in blue, were stained with DAPI. Photos were taken using an epifluorescence microscope at ×20. More information can be found in the Communication by T. L. Mindt, A. G. Tzakos, et al. (DOI: doi.org/10.1002/chem.20200092410.1002/chem.202000924).

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Eirinaios I. Vrettos, Ibai E. Valverde, Alba Mascarin, Patrick N. Pallier, Linda Cerofolini, Marco Fragai, Giacomo Parigi, Baydaa Hirmiz, Nick Bekas, Nathalie M. Grob, Evgenios Κ. Stylos, Hamidreza Shaye, Mark Del Borgo, Marie‐Isabel Aguilar, Francesca Magnani, Nelofer Syed, Timothy Crook, Emal Waqif, Essam Ghazaly, Vadim Cherezov, Robert E. Widdop, Claudio Luchinat, Adina T. Michael‐Titus, Thomas L. Mindt, Andreas G. Tzakos
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202003569

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Synthetic Approaches to Fluoroalkyltelluryl‐Substituted Compounds

Synthetic Approaches to Fluoroalkyltelluryl‐Substituted Compounds

CF3O, CF3S, and CF3Se chemistries have been widely described in the last years. Tellurium is the following chalcogen but the CF3Te chemistry remains poorly described. This review presents the different strategies and methods currently available.

Fluorinated substituents confer specific properties to molecules. In the last years, the merging of chalcogenes with trifluoromethyl or fluoroalkyl moieties has known a growing interest. However, the last non‐radioactive family member, namely tellurium, did not receive much attention. This review will present and discuss the state of the art chemistry of RFTe, to describe the available methods and highlight the future developments to consider.

Wiley: European Journal of Organic Chemistry: Table of Contents
Authors: Kevin Grollier, Alexis Taponard, Thierry Billard
doi.org/10.1002/ejoc.202000839

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KI‐Mediated One‐Pot Transition‐Metal‐Rree Synthesis of 4‐Phenylpyrrolo[1,2‐a]quinoxalines

KI‐Mediated One‐Pot Transition‐Metal‐Rree Synthesis of 4‐Phenylpyrrolo[1,2‐a]quinoxalines

This protocol offered an eco‐friendly and convenient method for the synthesis of pyrrolo[1,2‐a ]quinoxalines. In this process, new C=N and C–C bond were formed in mild conditions. A series of pyrrolo[1,2‐a ]quinoxaline derivatives were obtained in moderate to good yields.

An efficient and eco‐friendly method for the synthesis of pyrrolo[1,2‐a ]quinoxalines is presented. Compared to previous methods, this protocol is transition‐metal‐free and only potassium iodide is required. A series of substituted 4‐phenylpyrrolo[1,2‐a ]quinoxalines are obtained in moderate to good yields.

Wiley: European Journal of Organic Chemistry: Table of Contents
Authors: Shichen Li, Caixia Xie, Xianglong Chu, Zhen Dai, Lei Feng, Chen Ma
doi.org/10.1002/ejoc.202000791

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Sublimation Kinetics for Individual Graphite and Graphene Nanoparticles (NPs): NP-to-NP Variations and Evolving Structure-Kinetics and Structure-Emissivity Relationships

TOC Graphic

Journal of the American Chemical Society

Journal of the American Chemical Society: Latest Articles (ACS Publications)
Authors: Bryan A. Long, Chris Y. Lau, Daniel J. Rodriguez, Susanna An Tang, and Scott L. Anderson*
feedproxy.google.com/~r/acs/jacsat/~3/qev2pAXA-do/jacs.0c01720

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