Angewandte Chemie International Edition

Upcoming Hot Papers

Hot Papers are chosen by the Editors for their importance in a rapidly evolving field of high current interest. Many of the "Very Important Papers" (VIPs) would certainly qualify to be included here, but such a duplication is avoided.

Porphyrin Analogues

Azacalixphyrin: The Hidden Porphyrin Cousin Brought to Light

Zhongrui Chen, Michel Giorgi, Denis Jacquemin*, Mourad Elhabiri, Olivier Siri*

No pyrrol: Azacalixphyrin (see picture), a novel isostructural and isoelectronic "pyrrol-free" analogue of porphyrins is easily prepared in two straightforward steps. The azacalixphyrin is aromatic, absorbs in the entire visible region, and is highly stable (even in the presence of water under air) owing to its unusual bis-zwitterionic character.

Coming soon.

 

Fluorogenic Probes

BODIPY–Tetrazine Derivatives as Superbright Bioorthogonal Turn-on Probes

Jonathan C. T. Carlson, Labros G. Meimetis, Scott A. Hilderbrand, Ralph Weissleder*

The fastest and the brightest: A new design that intimately connects tetrazine to a BODIPY fluorophore enables exceptionally efficient energy transfer and quenching. Upon reaction of the tetrazine, the brightness of the fluorophore increases more than a thousand-fold, which is a fluorogenic activation up to two orders of magnitude greater than previously described.

Coming soon.

 

Targeted Delivery

A Reactive Oxygen Species (ROS)-Responsive Polymer for Safe, Efficient, and Targeted Gene Delivery in Cancer Cells

Min Suk Shim, Younan Xia*

Stimuli-responsive release: The high levels of reactive oxygen species (ROS) in prostate cancer cells can be exploited to trigger cancer-targeted gene delivery. A ROS-responsive thioketal-based cationic polymer was synthesized and functionalization with a cancer-targeting peptide led to selective and enhanced gene transfection in prostate cancer cells (see scheme).

Coming soon.

 

Radical Chemistry

Single and Double N–H Bond Activation of Ammonia by [Al₂O₃]·⁺: Room Temperature Formation of the Aminyl Radical and Nitrene

Robert Kretschmer, Zhe-Chen Wang, Maria Schlangen, Drs. h. c. Helmut Schwarz*

Crime scene: N–H bond activation. When ammonia gets in the crosshairs of [Al₂O₃]·⁺ the reaction is not limited to a single hydrogen-atom transfer, double hydrogen abstraction takes place as well and free nitrene is liberated at room temperature. These results are confirmed by mass spectrometric and theoretical investigations.

Published online, DOI: 10.1002/anie.201302506 – Read now

 

Nitrous oxide

Oxidative Coupling Reactions of Grignard Reagents with Nitrous Oxide

Gregor Kiefer, Lo[iuml]c Jeanbourquin, Kay Severin*

Catalysis with laughing gas: N₂O in combination with transition-metal catalysts allow the oxidative homo- and cross-coupling of Grignard reagents. The reactions can be performed under mild conditions despite the inert character of N₂O.

Published online, DOI: 10.1002/anie.201302471 – Read now

 

Photoactivatable Lipids

The Fatty Acid Composition of Diacylglycerols Determines Local Signaling Patterns

André Nadler, Gregor Reither, Suihan Feng, Frank Stein, Sabine Reither, Rainer Müller, Carsten Schultz*

Caged compounds are designed to release biologically active signaling molecules with temporal, spatial, and even subcellular resolution. But how localized does the signal stay? Using the example of diacylglycerol, some signal responses (PKC) are shown to remain spatially distinct while other signals ([Ca²⁺]_i) spread across the entire cell. Surprisingly, this distribution patterns depend on the fatty acid composition of the lipid species.

Coming soon.

 

Ionic Silicon(II) Compounds

Silicon(II) Coordination Chemistry: N-Heterocyclic Carbene Complexes of Si²⁺ and SiI⁺

Alexander C. Filippou*, Yury N. Lebedev, Oleg Chernov, Martin Straßmann, Gregor Schnakenburg

Ligand swap: The exchange of N-heterocyclic carbene (NHC) ligands at Si^II centers is shown to provide access to a dicationic NHC complex of silicon(II), and an NHC adduct of the iodosilyliumylidene cation SiI⁺, [SiI(IiPr₂Me₂)(IDipp)]⁺ (see picture). Characterization studies led to the discovery of an unprecedented C–H···Si anagostic interaction for [SiI(IiPr₂Me₂)(IDipp)]⁺.

Coming soon.

 

Conducting Materials

Using Stable Radicals To Protect Pentacene Derivatives from Photodegradation

Yusuke Kawanaka, Akihiro Shimizu, Tetsuro Shinada, Rika Tanaka, Yoshio Teki*

A radical solution: The photochemical instability and insolubility in organic solvents of pentacene derivatives prevent their use in molecular electronics. These issues were solved by using pentacene derivatives with stable radicals (Y=radical moiety, 2 and 4) that have a lifetime of 2077 min in organic solvents under ambient light. The corresponding nonradical pentacene derivatives (Y=radical precursor, 1 and 3) decay on exposure to light.

Published online, DOI: 10.1002/anie.201300595 – Read now

 

Stereoselective Rearrangement

Stereoselective Rearrangements with Chiral Hypervalent Iodine Reagents

Umar Farid, Florence Malmedy, Romain Claveau, Lena Albers, Thomas Wirth*

I likes rearrangements: Hypervalent iodine compounds can be used as environmentally friendly, mild, and selective reagents for highly enantioselective rearrangements of alkenes. For the first time, rearrangements to α-arylated ketones can be performed enantioselectively using lactic acid-based iodine(III) reagents.

Published online, DOI: 10.1002/anie.201302358 – Read now

 

Polymer Capsules

Preparation of Nano- and Microcapsules by Electrophoretic Polymer Assembly

Joseph J. Richardson, Hirotaka Ejima, Samuel L. Lörcher, Kang Liang, Philipp Senn, Jiwei Cui, Frank Caruso*

Slipping into a comfortable routine: Multilayered polymer thin films were assembled on particles immobilized in agarose by electrophoresis on the basis of various interactions. Core removal then led to robust capsules with different polymer compositions (see fluorescence image). This approach enables the versatile and routine assembly of nanometer- and micron-sized capsules and coated particles with very few processing steps.

Published online, DOI: 10.1002/anie.201302092 – Read now

 

Organozinc Reagents

Functionalized Alkenylzinc Reagents Bearing Carbonyl Groups: Preparation by Direct Metal Insertion and Reaction with Electrophiles

Christoph Sämann, Matthias A. Schade, Shigeyuki Yamada, Paul Knochel*

Highly functionalized cyclic and acyclic alkenylzinc reagents bearing functional groups such as aldehyde, keto, and ester groups were readily prepared by either direct zinc insertion in the presence of LiCl or by magnesium insertion in the presence of LiCl and ZnCl₂. Subsequent functionalization reactions like Negishi cross-couplings, acylations, and allylations were performed, furnishing polyfunctional compounds in excellent yields.

Published online, DOI: 10.1002/anie.201302058 – Read now

 

Heterogeneous Photocatalysis

Oxidation of Water under Visible-Light Irradiation over Modified BaTaO₂N Photocatalysts Promoted by Tungsten Species

Kazuhiko Maeda*, Daling Lu, Kazunari Domen*

Water splitting: In heterogeneous photocatalysis, it has been believed that doping transition-metal cations having partly filled d orbitals into semiconductor photocatalysts results in a significant drop in photocatalytic activity. Nevertheless, it was found that the activity for the water oxidation of BaTaO₂N could be improved by seven times upon modification by pentavalent W species (see picture).

Published online, DOI: 10.1002/anie.201301357 – Read now

 

Gold Catalysis

Gold(I)-Catalyzed Cascade Cycloadditions between Allenamides and Carbonyl-Tethered Alkenes: An Enantioselective Approach to Oxa-Bridged Medium-Sized Carbocycles

Hélio Faustino, Isaac Alonso, José L. Mascareñas*, Fernando López*

Gold standard: Allenamides react with aldehydes or ketones having γ, δ, or [epsiv] alkenyl groups, upon activation with suitable gold catalysts, to provide oxa-bridged systems containing seven- to nine-membered carbocycles, in a formal cascade cycloaddition. By using chiral phosphoramidite/gold or bisphosphine/gold catalysts it is possible to obtain the oxa-bridged seven- and eight-membered rings with good to high enantioselectivities.

Published online, DOI: 10.1002/anie.201302713 – Read now

 

Nanoparticles for Stem Cells

Multimodal Magnetic Core–Shell Nanoparticles for Effective Stem-Cell Differentiation and Imaging

Birju Shah, Perry T. Yin, Shraboni Ghoshal, Ki-Bum Lee*

Special delivery! The title system, composed of a highly magnetic core surrounded by a thin uniform gold shell, has been synthesized and applied to the magnetically facilitated delivery of genetic material (siRNA or plasmid DNA) into neural stem cells (NSCs) for controlling their neural differentiation in a spatiotemporally controlled, biocompatible manner.

Published online, DOI: 10.1002/anie.201302245 – Read now

 

Micromotors

Chemotactic Behavior of Catalytic Motors in Microfluidic Channels

Larysa Baraban, Stefan M. Harazim, Samuel Sanchez*, Oliver G. Schmidt

Chemotaxis in practice: Two different artificial catalytic micromotors (tubular and spherical, see scheme) show chemotactic behavior in microfluidic channels demonstrating that catalytic micromotors can sense the gradient of chemical fuel in their environment and be directed towards desired locations.

Published online, DOI: 10.1002/anie.201301460 – Read now No. 21/2013.

 

Lithium Ion Battery

Catalyst-free Direct Growth of a Single to a Few Layers of Graphene on a Germanium Nanowire for the Anode Material of a Lithium Battery

Hyungki Kim, Yoonkook Son, Chibeom Park, Jaephil Cho*, Hee Cheul Choi*

Direct growth of a single to a few layers of graphene on a germanium nanowire (Gr/Ge NW; see picture) was achieved by a metal-catalyst-free chemical vapor deposition (CVD) process. The Gr/Ge NW was used as anode in a lithium ion battery. This material has a specific capacity of 1059 mA h g⁻¹ at 4.0 C, a long cycle life over 200 cycles, and a high capacity retention of 90 %.

Published online, DOI: 10.1002/anie.201300896 – Read now

 

Cooperative Catalysis

An Efficient Approach to the Securinega Alkaloids Empowered by Cooperative N-Heterocyclic Carbene/Lewis Acid Catalysis

Adel M. ElSohly, Daniel A. Wespe, Tyler J. Poore, Scott A. Snyder*

Folding it all together: Most of the syntheses developed for the securinega alkaloid class require lengthy sequences to create their bridging butenolide domains. A novel approach uses
N-heterocyclic carbenes (NHCs) and Lewis acids to forge the entire domain in a single step from appropriate precursors, showing that ynal-derived homoenolates can participate as nucleophiles in intramolecular settings (see scheme).

Published online, DOI: 10.1002/anie.201301849 – Read now No. 22/2013.

 

Fluorinated Compounds

Manganese-Catalyzed Oxidative Benzylic C–H Fluorination by Fluoride Ions

Wei Liu, John T. Groves*

An efficient protocol for the selective fluorination of benzylic C–H bonds is described. The process is catalyzed by manganese salen complexes and uses nucleophilic fluorine sources, such as triethylamine trihydrofluoride and KF. Reaction rates are sufficiently high (30 min) to allow adoption for the incorporation of ¹⁸F fluoride sources for PET imaging applications.

Published online, DOI: 10.1002/anie.201301097 – Read now

 

Cleaving Amines by Water

Direct Deamination of Primary Amines by Water to Produce Alcohols

Julia R. Khusnutdinova, Yehoshoa Ben-David, David Milstein*

Just add water! The title reaction is catalyzed by an acridine-based pincer complex (1, see scheme). This one-step transformation uses water as the only reagent in the absence of additional bases, oxidants, or reductants. Cyclization of 1,4-diaminobutane and 1,6-diaminohexane catalyzed by 1 leads to the formation of pyrrolidine and azepane, respectively.

Published online, DOI: 10.1002/anie.201301000 – Read now

 

Asymmetric Synthesis

Cinchona Alkaloid Amide/Copper(II) Catalyzed Diastereo- and Enantioselective Vinylogous Mannich Reaction of Ketimines with Siloxyfurans

Masashi Hayashi, Masahide Sano, Yasuhiro Funahashi, Shuichi Nakamura*

Managing the Mannich: The first enantioselective vinylogous Mannich reaction of siloxyfurans with ketimines derived from unactivated ketones has been developed. Excellent yields and enantioselectivities were obtained using a new class of readily accessible cinchona alkaloid amide/Cu(OAc)₂ catalysts on a range of substrates.

Published online, DOI: 10.1002/anie.201301917 – Read now No. 21/2013.

 

Dye-Sensitized Solar Cells

Stable Dye-Sensitized Solar Cell Electrolytes Based on Cobalt(II)/(III) Complexes of a Hexadentate Pyridyl Ligand

Muhammad K. Kashif, Michael Nippe, Noel. W. Duffy, Craig M. Forsyth, Christopher J. Chang*, Jeffrey R. Long*, Leone Spiccia*, Udo Bach*

Energy conversion: A cobalt redox mediator, [Co(bpyPY4)]^2+/3+, based on a hexadentate polypyridyl ligand, was developed. Dye-sensitized solar cells (DSCs) made with this redox mediator showed improved stability and slightly higher efficiencies compared to [Co(bpy)₃]^2+/3+-based devices. Long-term stability evaluation of DSCs based on [Co(bpyPY4)]^2+/3+ revealed excellent stability under full irradiation conditions (see picture).

Published online, DOI: 10.1002/anie.201300070 – Read now No. 21/2013.

 

Internalization Sensor

A Programmable Sensor to Probe the Internalization of Proteins and Nanoparticles in Live Cells

Haiyin Liu, Angus P. R. Johnston*

A molecular sensor has been developed to probe the internalization of proteins and nanoparticles into live cells. This simple, high-throughput technique is compatible with cell phenotyping and is independent of the cellular fate of the material.

Published online, DOI: 10.1002/anie.201301243 – Read now No. 22/2013.

 

Carbon–Carbon Bond Cleavage

Silver-Catalyzed Nitrogenation of Alkynes: A Direct Approach to Nitriles through C≡C Bond Cleavage

Tao Shen, Teng Wang, Chong Qin, Ning Jiao*

Three in one blow! A novel direct transformation of alkynes into nitriles by a silver-catalyzed nitrogenation reaction through C≡C bond cleavage has been developed. This research provides both a new application for alkynes in organic synthesis, and valuable mechanistic insights into nitrogenation chemistry.

Published online, DOI: 10.1002/anie.201300193 – Read now

 

Quantum Simulator

Hexamethoxyphenalenyl as a Possible Quantum Spin Simulator: An Electronically Stabilized Neutral π Radical with Novel Quantum Coherence Owing to Extremely High Nuclear Spin Degeneracy

Akira Ueda, Shuichi Suzuki, Kenta Yoshida, Kozo Fukui, Kazunobu Sato, Takeji Takui*, Kazuhiro Nakasuji, Yasushi Morita*

A phenalenyl radical with six methoxy groups, which were introduced symmetrically, has been synthesized. The extensively delocalized and highly symmetric electronic-spin system was studied with advanced cw-/pulsed-ESR techniques, thereby giving an experimental model to explore molecular quantum spin simulators with novel quantum coherence attributable to the extremely high degeneracy of the nuclear spin states owing to the eighteen equivalent protons.

Published online, DOI: 10.1002/anie.201301435 – Read now

 

Homogeneous Catalysis

A General Catalytic Methylation of Amines Using Carbon Dioxide

Yuehui Li, Xianjie Fang, Kathrin Junge, Matthias Beller*

Putting CO₂ to work: Carbon dioxide is shown to be a general and selective methylating reagent for secondary and primary, aromatic and aliphatic amines under reductive conditions. A variety of tertiary amines are obtained from CO₂ and commercially available silanes in high yields with good tolerance to nitrile, olefin, ether, ester, and hydroxy groups.

Published online, DOI: 10.1002/anie.201301349 – Read now

 

Protein Array in Cells

A Protein-Interaction Array Inside a Living Cell

Silke Gandor, Stephanie Reisewitz, Muthukumaran Venkatachalapathy, Giuseppe Arrabito, Martina Reibner, Hendrik Schröder, Katharina Ruf, Christof M. Niemeyer, Philippe I. H. Bastiaens*, Leif Dehmelt*

Taking the bait: Protein interaction arrays were generated in living cells by the interaction of bait-presenting artificial receptor constructs (bait-PARCs) with micrometer-scaled antibody surface patterns (see figure). This method was applied to simultaneously monitor the interaction kinetics of a prey protein with two distinct bait proteins in individual living cells.

Published online, DOI: 10.1002/anie.201209127 – Read now