Archive for October, 2011

Further insight into aromatic borylation chemistry

Thorough characterisation of arene–borane Lewis acid contacts is essential for understanding the mechanistic pathway for aromatic borylation chemistry and by extension, electrophilic aromatic substitution. However, until now, structural determination of such arene–borane compounds has been somewhat ambiguous.

Simon Aldridge and his team have set out to fill this knowledge gap by reacting a sterically encumbered pyridine donor with BBr3 to yield a cationic tri-coordinate borane–arene complex. Employing crystallography and computational studies, the team found that a weak electrostatic interaction is responsible for the short contacts between the positively charged boron centre and the arene π system.

Read the ChemComm article to find out more…

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Metal evasion still leads to nitration

Researchers from Germany and China have designed a simple method for forming nitroarenes.

Aromatics substituted with nitro groups are ubiquitous motifs in important molecules required by the textiles, materials and pharmaceutical industries. 

However, installing nitro groups can be tricky because it requires the use of strong acids or dinitrogen peroxide. These harsh conditions are not commonly tolerated by sensitive functionality present in molecules, and problems of selectivity or over-nitration commonly arise.  Alternate methods use large quantities of silver salts or expensive palladium catalysts. 

Now Xiao-Feng Wu (Zhejiang Sci-Tech University, China), Matthias Beller (Leibniz Institute for Catalysis, Germany) and colleagues have designed a metal-free method for nitrating aryl boronic acids.

nitration of aryl boronic acids

The team used an alkyl nitrite at 80 ˚C to convert the boronic acid group to a nitro group. The reaction works in moderate to good yields for electron-rich and electron-neutral aryl boronic acids. Electron-poor aromatics are more challenging substrates, as the boronic acid are less reactive. 

While this method is not yet suitable for vinyl or hydroxy substituted aryl boronic acids, it offers an economically and operationally attractive method for synthesising nitro compounds.

Researcher’s perspective:Our initial investigations started with the use of a rhodium catalyst, because of rhodium’s known ability to transmetalate with arylboronic acid. Our target product, nitrobenzene, was formed but we found that the rhodium catalyst is not necessary for this transformation.

On one hand, we were disappointed, as our aim is to develop catalytic reactions; on the other hand, we are happy, because this reaction works so nicely.

Xiao-Feng Wu

Using this method, nitroarenes can be easily prepared from arylboronic acids without using catalyst and hazardous reagents.

More information can be found in the ChemComm communication, free to download for a limited period.

Posted on behalf of Alice E. Williamson, ChemComm web writer.

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Supramolecular assembly of polyoxometalate triangles

Polyoxometalates (POMs) are a diverse class of inorganic materials that are of great interest due to their exciting range of redox, conducting, magnetic and catalytic properties. Recent collaborative work from Professor Garry Hanan in Montreal and Professor Bernold Hasenknopf in Paris reports the inclusion of a Lindqvist-type hexavanadate POM as a component of a self-assembling supramolecular framework.

They designed ligand 1 utilising a triol motif to complex the POM in combination with pyridyl groups to serve as binding sites for a transition metal. The reaction of 1 with a suitable decavanadate yielded complex 2, a hexavanadate POM complex that is itself a structurally rigid and spatially well-defined bi-pyridyl ligand. The 60° angle between the coordination vectors of the pyridyl groups led the authors to predict that the coordination of a trans-PdCl2 unit by 2 would result in a supramolecular triangle.

supramolecular assembly of polyoxometalate triangles

Initially the reaction of 2 with [PdCl2(CH3CN)2] in DMAc yielded a complex mixture of products; however, heating to 80 °C for 48 hours led to just a single assembly. This was shown by a number of analytical techniques to be the predicted triangular assembly 3.

This work elegantly uses a classical motif for self-assembly to create a multi-component supramolecular architecture. It is a great step towards the goal of creating functional supramolecular arrays, integrating the desirable properties of POMs into a new framework and bridging the gap between solid state oxides and coordination chemistry.

Researcher’s perspective:
The obtention of discrete coordination-driven POM-based arrays had so far eluded the community, with only a few well characterised coordination polymers. We started this challenging project of a molecular triangle by a simple drawing based on geometrical considerations. A range of conditions were explored, but most lead to complex mixtures except one. This identification of optimal conditions was our first satisfaction. However, we needed solid evidence of the triangular nature of the obtained array to validate our approach as a rational design: a combination of techniques confirmed the successful and selective synthesis of the triangle. As a student, I learnt a lot from the complementary competencies provided by the two groups on a project at the interface of inorganic, organic, supramolecular and coordination chemistry. Dealing with the specific difficulties of each domain has been an exciting challenge that has re-confirmed my choice in academic research. Marie-Pierre Santoni, a student in the research collaboration

To read more about Hanan and Hasenknopf’s work, download their ChemComm article.

Posted on behalf of Cally Haynes, ChemComm web writer.

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65 days until 100 issues…

….and did you know….?

There are 65 articles in ChemComm’s ‘Selective Catalysis for Organic Synthesis’ web themed issue. This was ChemComm’s first web theme, published back in 2009. Since then, we’ve published a host of exciting themes, all of which are available to browse on the ChemComm website.

Do you have an idea for a web theme? Get in touch with us by email, Twitter or leave your comments below.

Also of interest:
100 days to 100 issues
96 days until 100 issues…
93 days until 100 issues…
81 days until 100 issues…
72 days until 100 issues…

70 days until 100 issues…

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70 days until 100 issues…

….and did you know?….

I’ve been working for RSC Publishing for 70 months, during which time I’ve worked on Physical Chemistry Chemical Physics, Faraday Discussions, Organic & Biomolecular Chemistry and Natural Product Reports before my move to ChemComm, Chem Soc Rev and Chemical Science in 2009.

To learn more about the people that work on ChemComm, visit our staff webpage.

Find out more about the move to 100 issues >

Also of interest:
100 days to 100 issues
96 days until 100 issues…
93 days until 100 issues…
81 days until 100 issues…
72 days until 100 issues…

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Highlights in Chemistry: short reviews from the brightest scientists

As the nights are drawing in here in Cambridge, it is nice to bring a little light in to our lives in the form of Highlights in Chemistry. 

Commissioned to celebrate the International Year of Chemistry 2011, these short reviews cover the most significant advances in the chemical sciences since the millennium. The topics include photocatalytic hydrogen production, nucleic acid sequencing, antibiotic resistance mechanisms, molecular machines and metathesis, to name just a few. 

We’ve nearly published all the Highlights in Chemistry so take a look at the collection on the ChemComm website. There are some fun graphical abstracts to accompany the articles – can you guess who supplied the images I’ve used in this blog? Click on the images to find out.

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72 days until 100 issues…

Journal cover: ….and did you know?….

Back in ‘72, the journal changed its name from Journal of the Chemical Society D: Chemical Communications to Journal of the Chemical Society, Chemical Communications.

It looked pretty different back then – someone liked green!

Find out more about the move to 100 issues >

Also of interest:
100 days to 100 issues
96 days until 100 issues…
93 days until 100 issues…
81 days until 100 issues…

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Top ten most accessed articles in September

This month sees the following articles in ChemComm that are in the top ten most accessed:-

Two metal–organic frameworks based on a double azolium derivative: post-modification and catalytic activity
Guo-Qiang Kong, Xuan Xu, Chao Zou and Chuan-De Wu
Chem. Commun., 2011, 47, 11005-11007, DOI: 10.1039/C1CC14393J

Design and in situ synthesis of a Cu-based porous framework featuring isolated double chain magnetic character
Chandan Dey, Raja Das, Binoy Krishna Saha, Pankaj Poddar and Rahul Banerjee
Chem. Commun., 2011, 47, 11008-11010, DOI: 10.1039/C1CC13418C

Enzyme-free colorimetric assay of serum uric acid
Raj Kumar Bera, Anakuthil Anoop and C. Retna Raj
Chem. Commun., 2011, 47, 11498-11500, DOI: 10.1039/C1CC13349G

Hydrogen bonded supramolecular polymers in moderately polar solvents
Farid Ouhib, Matthieu Raynal, Benjamin Jouvelet, Benjamin Isare and Laurent Bouteiller
Chem. Commun., 2011, 47, 10683-10685, DOI: 10.1039/C1CC14590H

Enantioselective synthesis of 2-methyl indolines by palladium catalysed asymmetric C(sp3)–H activation/cyclisation
Saithalavi Anas, Alex Cordi and Henri B. Kagan
Chem. Commun., 2011, 47, 11483-11485, DOI: 10.1039/C1CC14292E

Highly tunable arylated cinchona alkaloids as bifunctional catalysts
Cormac Quigley, Zaida Rodríguez-Docampo and Stephen J. Connon
Chem. Commun., 2012, Advance Article, DOI: 10.1039/C1CC14684J

A FRET-based indicator for imaging mitochondrial zinc ions
Kesavapillai Sreenath, John R. Allen, Michael W. Davidson and Lei Zhu
Chem. Commun., 2011, 47, 11730-11732, DOI: 10.1039/C1CC14580K

Photo-driven anti-Markovnikov alkyne hydration in self-assembled hollow complexes
Takashi Murase, Hiroki Takezawa and Makoto Fujita
Chem. Commun., 2011, 47, 10960-10962, DOI: 10.1039/C1CC14523A

Nitroolefin-based coumarin as a colorimetric and fluorescent dual probe for biothiols
Yuan-Qiang Sun, Maliang Chen, Jing Liu, Xin Lv, Jun-fei Li and Wei Guo
Chem. Commun., 2011, 47, 11029-11031, DOI: 10.1039/C1CC14299B

Potassium tert-butoxide mediated Heck-type cyclization/isomerization–benzofurans from organocatalytic radical cross-coupling reactions
Magnus Rueping, Matthias Leiendecker, Arindam Das, Thomas Poisson and Lan Bui
Chem. Commun., 2011, 47, 10629-10631, DOI: 10.1039/C1CC14297F

Why not take a look at the articles today and blog your thoughts and comments below.

Fancy submitting an article to ChemComm? Then why not submit to us today or alternatively contact us your suggestions.

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Worm-like peptides form gels at physiological pH

Salt can induce gelation of functionalised dipeptides at high pH, say a team of scientists from the UK and France. The finding will significantly expand the utility of hydrogels, they claim. 

Hydrogels are formed when molecules assemble into nanofibres, which then entangle and form a gel matrix. They can be used for a variety of applications, including drug delivery and scaffolds for tissue engineering. Peptide-based gelators are of particular interest at present, in part because they are potentially biocompatible. 

Gelation is commonly triggered by pH, temperature or solvent composition. Dave Adams, at the University of Liverpool, and colleagues discovered that functionalised dipeptides that adopt a worm-like micelle structure at high pH form gels when salts are added to them. High pH is normally outside the window for gelation so the finding could be very useful for the field. Importantly, now that these gels can be made at physiological pH, they should find increased use in bioapplications.

Graphical abstract: Salt-induced hydrogelation of functionalised-dipeptides at high pH

Read more in Adams’ ChemComm communication, free to access for a limited period.

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Easy xenon capture and release using MOFs

Graphical abstract: Facile xenon capture and release at room temperature using a metal–organic framework: a comparison with activated charcoalXenon is naturally present in very small amounts in the atmosphere but radioactive forms are released following nuclear detonations, reprocessing and explosions, such as the recent catastrophe at Fukushima Daiichi Nuclear Power Plant in Japan. Xenon is also used in a variety of other applications, from lighting to medical imaging, so capturing and separating it (from its sister noble gas krypton) is important for both commercial uses and atmospheric monitoring.

Praveen Thallapally, at Pacific Northwest National Laboratory, Richland, US, and colleagues made two well-known metal–organic frameworks (MOFs) known as MOF-5 and NiDOBDC and compared their ability to capture and separate xenon with activated carbon. They found that NiDOBDC adsorbs significantly more xenon than MOF-5, and is more selective for xenon over krypton than activated carbon.

To find out more, download Dr Thallapally’s ChemComm communication.

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