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Improved organocatalyst

12 Sep 2012

UK scientists have developed a scalable, resolution-free synthesis of a helical DMAP organocatalyst.

In 2011 Dave Carbery (University of Bath) and colleagues made a helicene catalyst that they say was the most active chiral DMAP-like nucleophilic catalyst (DMAP = 4-dimethylamino pyridine). It was an effective catalyst for the acylative kinetic resolution of chiral secondary alcohols. With it, the team achieved reactions on a gram scale using only 1mg of catalyst – a 0.05mol% loading. However, the catalyst needed HPLC resolution.

They are now able to make more than 1g of the helical DMAP without any resolution. They say that it is also possible to do late-stage functionalisation.

Link to journal article
Point-to-helical chirality transfer for a scalable and resolution-free synthesis of a helicenoidal DMAP organocatalyst
M R Crittall, N W G Fairhurst and D R Carbery
Chem. Commun., 2012, DOI: 10.1039/c2cc35583c

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Refinery test for mesostructured zeolite

12 Sep 2012

The Y zeolite is used as a catalyst for fluid catalytic cracking. It has a high surface area and large pores and is thermally and hydrothermally stable. But scientists are working on improving the catalyst for a better performance. One reason is that the 7.4Å micropores are limited in terms of size of hydrocarbon that they can take in. The process involves diffusion of large hydrocarbon molecules into the crystals and diffusion of the desired intermediate cracking products (diesel or light oil, gasoline and liquefied petroleum gases) out.

Introducing wider pores allows large hydrocarbon molecules to go through the process. Scientists from Spain had recently carried out a templating process (using a surfactant) to introduce highly controlled mesoporosity into zeolites. This led to improved catalytic selectivity, in which more gasoline, light oil and liquefied petroleum gas were obtained.

The team have now scaled up the catalyst and tested its hydrothermal stability and catalytic cracking performance in a refinery. The catalyst showed much better product selectivity compared to the current catalyst, says the team.

Link to journal article
A mesostructured Y zeolite as a superior FCC catalyst – from lab to refinery
J Garcia-Martinez, K Li and G Krishnaiah
Chem. Commun., 2012, DOI: 10.1039/c2cc35659g

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Nominations invited for ChemComm Emerging Investigator Lectureship 2013

05 Sep 2012

We are delighted to invite nominations for ChemComm Emerging Investigator Lectureship 2013. The lectureship, which is awarded annually, will recognise an emerging scientist in the early stages of their independent academic career.

To qualify
To be eligible for the ChemComm Emerging Investigator Lectureship, the candidate should have completed their PhD on or after 5th September 2004.

The candidate should also have published at least one article in ChemComm during the course of their independent career.

Award details
The recipient of the award will be invited to present a lecture at three different locations over a 12 month period. It is expected that at least one of the locations will be a conference. The recipient will receive a contribution of £1500 towards travel and accommodation costs. S/he will also be presented with a certificate and be asked to contribute a ChemComm Feature Article.

Nominations
Those wishing to make a nomination should send the following details to the ChemComm Editorial Office by 7th December 2012:

Recommendation letter, including the name, contact details and website URL of the nominee.
A one page CV for the nominee, including their date of birth, summary of education and career, list of up to five independent publications, total numbers of publications and patents and other indicators of esteem and evidence of independence.
A copy of the candidate’s best publication to date (as judged by the nominator).
Two supporting letters of recommendation from two independent referees. These should not be someone from the same institution or the candidate’s post doc or PhD supervisor.

The nominator and independent referees are requested to comment on the candidate’s presenting skills.

Please note that self nomination is not permitted.

Selection procedure
The ChemComm Editorial Board will draw up a short-list of candidates based on the information provided by the referees and nominator. Short-listed candidates will be asked to provide a supporting statement justifying why they deserve the award. The recipient of the award will then be selected and endorsed by the ChemComm Editorial Board.

Previous winners

	2012 Professor Hiromitsu Maeda (Ritsumeikan University, Japan) – he’ll be presented with his lecture certificate at ICPOC 21.
	2011 Dr Scott Dalgarno (Heriot-Watt University, Edinburgh, UK) – Find out about his Emerging Investigator Lecture tour in China.

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Organometallics in catalysis: an article collection

31 Aug 2012

Perhaps the most well-known applications of organometallics in catalysis are the Ziegler–Natta catalysts which are used to generate polymers; the catalysts are made up of mixtures of transition metal halides and organo-aluminium complexes. Karl Ziegler and Giulio Natta were awarded the 1963 Nobel Prize in Chemistry for their discovery and development of the catalysts, which today are the most commonly used catalysts for the manufacture of polythene.

The esteemed history of organometallics is not to be under-estimated and includes Grignard’s reagents, the Heck reaction, Schrock catalysts, Grubbs’ catalysts and the Suzuki Coupling to name just a few. Organometallic compounds have revolutionised science and industry and to keep you up to date with the latest break-through research being made across all areas of organometallics in catalysis, we have made this cross-journal article collection free until 26^th September.

Organometallic hydrogen transfer and dehydrogenation catalysts for the conversion of bio-renewable alcohols, Andrew C. Marr, Catal. Sci. Technol., 2012, 2, 279-287

Synthesis of functionalized thiophenes and oligothiophenes by selective and iterative cross-coupling reactions using indium organometallics, M. Montserrat Martínez, Miguel Peña-López, José Pérez Sestelo and Luis A. Sarandeses, Org. Biomol. Chem., 2012, 10, 3892-3898

Homogeneous and heterogeneous catalysts for multicomponent reactions, Maria José Climent, Avelino Corma and Sara Iborra, RSC Adv., 2012, 2, 16-58

Amine directed Pd(II)-catalyzed C–H bond functionalization under ambient conditions, Benjamin Haffemayer, Moises Gulias and Matthew J. Gaunt, Chem. Sci., 2011, 2, 312-315

Metal–ligand bifunctional activation and transfer of N–H bonds, Kilian Muñiz, Anton Lishchynskyi, Jan Streuff, Martin Nieger, Eduardo C. Escudero-Adán and Marta Martínez Belmonte, Chem. Commun., 2011, 47, 4911-4913

Symmetrical and unsymmetrical pincer complexes with group 10 metals: synthesis via aryl C–H activation and some catalytic applications, Jun-Long Niu, Xin-Qi Hao, Jun-Fang Gong and Mao-Ping Song, Dalton Trans., 2011, 40, 5135-5150

Well-defined copper(I) complexes for Click azide–alkyne cycloaddition reactions: one Click beyond, Silvia Díez-González, Catal. Sci. Technol., 2011, 1, 166-178

Access to chiral α-bromo and α-H-substituted tertiary allylic alcohols via copper(I) catalyzed 1,2-addition of Grignard reagents to enones, Ashoka V. R. Madduri, Adriaan J. Minnaard and Syuzanna R. Harutyunyan, Org. Biomol. Chem., 2012, 10, 2878-2884

Catalytic versus stoichiometric dehydrocoupling using main group metals, Robert J. Less, Rebecca L. Melen and Dominic S. Wright, RSC Adv., 2012, 2, 2191-2199

An improved catalyst architecture for rhodium(III) catalyzed C–H activation and its application to pyridone synthesis, Todd K. Hyster and Tomislav Rovis, Chem. Sci., 2011, 2, 1606-1610

Continuous flow organometallic catalysis: new wind in old sails, Ulrich Hintermair, Giancarlo Franciò and Walter Leitner, Chem. Commun., 2011, 47, 3691-3701

Organometallic reactivity: the role of metal–ligand bond energies from a computational perspective, Natalie Fey, Benjamin M. Ridgway, Jesús Jover, Claire L. McMullin and Jeremy N. Harvey, Dalton Trans., 2011, 40, 11184-11191

An introduction to X-ray absorption spectroscopy and its in situ application to organometallic compounds and homogeneous catalysts, Ryan C. Nelson and Jeffrey T. Miller, Catal. Sci. Technol., 2012, 2, 461-470

Palladium-catalyzed cross-coupling reactions of organogold(I) phosphanes with allylic electrophiles, Miguel Peña-López, Miguel Ayán-Varela, Luis A. Sarandeses and José Pérez Sestelo, Org. Biomol. Chem., 2012, 10, 1686-1694

Transition metal complexes with strong absorption of visible light and long-lived triplet excited states: from molecular design to applications, Jianzhang Zhao, Shaomin Ji, Wanhua Wu, Wenting Wu, Huimin Guo, Jifu Sun, Haiyang Sun, Yifan Liu, Qiuting Li and Ling Huang, RSC Adv., 2012, 2, 1712-1728

Mechanism of the gold-catalyzed cyclopropanation of alkenes with 1,6-enynes, Patricia Pérez-Galán, Elena Herrero-Gómez, Daniel T. Hog, Nolwenn J. A. Martin, Feliu Maseras and Antonio M. Echavarren, Chem. Sci., 2011, 2, 141-149

A dual organic/organometallic approach for catalytic ring-opening polymerization, Estefanía Piedra-Arroni, Pierre Brignou, Abderrahmane Amgoune, Sophie M. Guillaume, Jean-François Carpentier and Didier Bourissou, Chem. Commun., 2011, 47, 9828-9830

Half-titanocenes for precise olefin polymerisation: effects of ligand substituents and some mechanistic aspects, Kotohiro Nomura and Jingyu Liu, Dalton Trans., 2011, 40, 7666-7682

Exploring the versatility of a bis(phosphinimine) pincer ligand: effect of sterics on structure and lactide polymerization activity of cationic zinc complexes, Craig A. Wheaton and Paul G. Hayes, Catal. Sci. Technol., 2012, 2, 125-138

Enantioselective Friedel–Crafts alkylation of indole derivatives catalyzed by new Yb(OTf)3-pyridylalkylamine complexes as chiral Lewis acids, Guillaume Grach, Aurelia Dinut, Sylvain Marque, Jérôme Marrot, Richard Gil and Damien Prim, Org. Biomol. Chem., 2011, 9, 497-503

Mononuclear and dinuclear complexes of manganese(III) and Iron(III) supported by 2-salicyloylhydrazono-1,3-dithiane ligand: synthesis, characterization and magnetic properties, Weiwei Zuo, Vitor Rosa, Clarisse Tourbillon, David Specklin, Cheaib Khaled, Mohamedally Kurmoo and Richard Welter, RSC Adv., 2012, 2, 2517-2526

Design and Preparation of New Palladium Precatalysts for C-C and C-N Cross-Coupling Reactions, Nicholas Bruno, Stephen Buchwald and Matthew T Tudge, Chem. Sci., 2012, Accepted Manuscript

Negishi cross-coupling of secondary alkylzinc halides with aryl/heteroaryl halides using Pd–PEPPSI–Ipent, Selçuk Çalimsiz and Michael G. Organ, Chem. Commun., 2011, 47, 5181-5183

Catalytic dehydrogenation of dimethylamine borane by group 4 metallocene alkyne complexes and homoleptic amido compounds, Torsten Beweries, Sven Hansen, Monty Kessler, Marcus Klahn and Uwe Rosenthal, Dalton Trans., 2011, 40, 7689-7692

Bimetallic aluminium(acen) complexes as catalysts for the synthesis of cyclic carbonates from carbon dioxide and epoxides, Michael North and Carl Young, Catal. Sci. Technol., 2011, 1, 93-99

Planar chiral (η5-cyclohexadienyl)- and (η6-arene)-tricarbonylmanganese complexes: synthetic routes and application, Francoise Rose-Munch and Eric Rose, Org. Biomol. Chem., 2011, 9, 4725-4735

Iron-catalysed reduction of carbonyls and olefins, Bryden A. F. Le Bailly and Stephen P. Thomas, RSC Adv., 2011, 1, 1435-1445

Palladium-catalyzed selective oxidative olefination and arylation of 2-pyridones, Yuye Chen, Fen Wang, Aiqun Jia and Xingwei Li, Chem. Sci., 2012, Advance Article

Hydrogenation of imino bonds with half-sandwich metal catalysts, Chao Wang, Barbara Villa-Marcos and Jianliang Xiao, Chem. Commun., 2011, 47, 9773-9785

Rational design of diphosphorus ligands – a route to superior catalysts, Jason A. Gillespie, Deborah L. Dodds and Paul C. J. Kamer, Dalton Trans., 2010, 39, 2751-2764

For even more articles, take a look at the Dalton Transactions Themed Issue d0 organometallics in catalysis or browse through over 30 RSC Journals covering topics across the chemical sciences.

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Magnetic mixed-metal molecules

22 Aug 2012

The first Re(IV) system incorporating a 4f ion has been reported by Martínez-Lillo and colleagues at the University of Edinburgh.

At present, molecular magnetism in heavy 4d, 5d and 4f-type metal ions is heavily researched since most known systems only involve 3d ions. Attempts to extend this research into the unexplored area of mixed 5d-4f systems has paid off with this discovery of a mixed Re(IV)-Gd(III) system.

Single crystals of the new compound, (NBu₄)₅[Gd{ReBr₄(μ-ox)}₄(H₂O)]·H₂O, were analysed at the ESRF to obtain a crystal structure. Magnetic studies were performed on the new compound, and significant intramolecular antiferromagnetic interactions were found to occur unambiguously between Re(IV) and Gd(III).

Further work on the preparation of the parent Re(IV)-Ln(III) complex will be carried out in the near future.

To read more about this new compound, its crystal structure and its intramolecular antiferromagnetic coupling, check out this HOT article (free to access for a limited period).

A heteropentanuclear oxalate-bridged [Re^IVGd^III] complex: synthesis, crystal structure and magnetic properties

José Martínez-Lillo, Laura Cañadillas-Delgado, Joan Cano, Francesc Lloret, Miguel Julve and Juan Faus

Posted on behalf of Katie Renouf, Chemical Communications web science writer.

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Supramolecular splicing: Catalytic fusion of supramolecules

22 Aug 2012

Non-covalent interactions dictate the assembly of many of nature’s most elegant structures. Similarly, supramolecular chemists have long been intrigued by the challenge of designing functional structures that spontaneously self-assemble from simpler fragments which mutually recognise each other.

A popular self-assembly approach is to produce coordination compounds from transition metal salts with rigid organic ligands. Directional bonding around transition metal centres allows the production of predictable and controllable shapes. Michael Schmittel’s group at the University of Siegen have been exploring a newer approach. They prepared two assemblies, a 2-component triangle T1 and a 3-component rectangle R1. The transition metal “corner” arrangements in T1 and R1 are disfavoured, so if the two assemblies are combined the components re-shuffle to form a more favourable assembly- the 5-component triangle T2. The transformation occurs at room temperature, and can be completed in just 1 hour in the presence of a catalyst, which accelerates the re-shuffling by labilising the metal-ligand bonds.

Supramolecular splicing: Catalytic fusion of supramolecules: re-shuffling of a 2-component triangle and a 3-component rectangle to give a more favoured supramolecular 5-component triangle

Unlike previous examples, the conditions needed for the transformation are very mild. The authors compare the process to gene shuffling, the combination of dissimilar genes to form new genetic material. The strategy could be considered a first step towards the evolution of supramolecular architectures, and a great route to more complex supramolecular assemblies with higher information content.

The full communication can be downloaded here (free to access for a limited period).

Cally Haynes

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Overcoat makes carbon quantum dots biocompatible

22 Aug 2012

Quantum dots are currently being developed for a variety of applications, including as sensors and cellular tags. Semiconductor quantum dots are attractive for their high fluorescence quantum yields but the toxicity of some of the metals involved, such as cadmium, pose a problem for biological applications.

Carbon quantum dots (CQDs) offer an alternative however when transferred into aqueous solution they possess low quantum yields. The problem is how do you harness the higher fluorescence of CQDs prepared in an organic solvent for biological applications?

To answer this question John Callan and his team have employed an amphiphilic polymer to act as an overcoat and transfer agent for the CQDs. Surprisingly they found that the transfer actually improved the quantum yield rather than the normally expected repression when ligand exchange is used. These aqueous carbon quantum dots were taken up into cells and were found to be non-toxic.

The development of inexpensive and biocompatible quantum dots with an improved quantum yield holds great potential for a wide range of future biological applications.

To find out more, download the ChemComm article today (free to access for a limited period).

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High yielding catenane synthesis? Surely not!

16 Aug 2012

Rapid thermally assisted donor–acceptor catenation

The X-ray crystal structures of two azide-functionalised catenanes

Entropy is not a friend of the macrocyclic chemist because creating large cyclic molecules by tying together several building blocks creates a high thermodynamic hurdle to cross. Nature has been forming these types of molecules for many millions of years and has provided inspiration for chemists to overcome these synthetic challenges. Perhaps purely for the academic interest, work began on investigating if it was possible to interlock two of these cyclic molecules together and form what is known as a catenane. Imagine a pot of spaghetti cooking and think of the strands tumbling around in the boiling water. Now imagine trying to tie all the ends together at the same time. Most will form individual rings but statistically a small number of those rings will be linked together. Conceptually this sounds easy but the reality is not so straight forward. A secondary problem is that only very small amounts of the linked rings are formed which means most of the starting material is wasted.

As interest in these curious molecules grew their potential application as switches for molecular electronics and sensors became apparent. However, if these applications were ever to be realised the cost of their formation would need to be feasible on a commercial scale. Macrocyclic chemists dream of yields over 50%, yet most chemists would be embarrassed to report a yield like this! However, we must remember that these reactions are inherently unfavourable so to achieve respectable yields we need to ‘stack the deck in our favour’ and try to make the interlocking of the rings more favourable.

Deceptively simple but incredibly effective ways of using what are commonly thought of as weak interactions have been used to hold the two fragments together, making the subsequent formation of the interlocked rings (rather than two separate rings) much more likely. In a recent report in Chemical Communications, Fraser Stoddart and co-workers at Northwestern University, Texas A&M University and the King Abdullah City for Science and Technology report a significant development in catenane synthesis whereby yields of almost 90% are possible. As almost quantitative conversions are now being reported the commercial application of these molecules, which has for so long been discussed, moves another step closer.

Rapid thermally assisted donor–acceptor catenation
Albert C. Fahrenbach, Karel J. Hartlieb, Chi-Hau Sue, Carson J. Bruns, Gokhan Barin, Subhadeep Basu, Mark A. Olson, Youssry Y. Botros, Abdulaziz Bagabas, Nezar H. Khdary and J. Fraser Stoddart
Chem. Commun., 2012,48, 9141-9143
DOI: 10.1039/C2CC34427K

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Lab-in-a-syringe approach to separating biomarkers from blood samples

16 Aug 2012

Scientists in China have developed a novel method to prepare ordered mesoporous silica fibres. The fibres can enrich endogenous peptides in under three minutes with a lab-in-syringe approach. The technique does not need electrical devices such as a centrifugal machine or vortex shaker.

The team says that the lab-in-syringe approach could be applied to separation sciences and it could be used in drug delivery, catalysis, and sensor and optical devices.

Electrospinning-based synthesis of highly ordered mesoporous silica fiber for lab-in-syringe enrichment of plasma peptides
Gangtian Zhu, Xiao-Shui Li, Xiao-Meng Fu, Juan-Yuan Wu, Bi-Feng Yuan and Y.-Q. Feng
DOI: 10.1039/C2CC34761J

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Cheaper dye-sensitised solar cells

16 Aug 2012

Scientists in Germany and Switzerland have used metal-free plastic cathodes to replace expensive transparent conducting oxide-coated electrodes in dye-sensitised solar cells.

The team says that a record metal-free plastic cathode cell performance of 4.22% can be achieved at full sun, which is 27% less than the standard value of platinised transparent conducting oxide-coated electrodes, but at a fraction of the cost.

Towards flexibility: Metal free plastic cathodes for Dye sensitized solar cells
Shahzada Ahmad, Elisa Dell’Orto, Jun-Ho Yum, Florian Kessler, Mohammad Khaja Nazeeruddin and Michael Gratzel
DOI: 10.1039/C2CC35038F

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Chemical Communications Blog

Archive for the ‘News’ Category

Improved organocatalyst

Refinery test for mesostructured zeolite

Nominations invited for ChemComm Emerging Investigator Lectureship 2013

Organometallics in catalysis: an article collection

Magnetic mixed-metal molecules

Supramolecular splicing: Catalytic fusion of supramolecules

Overcoat makes carbon quantum dots biocompatible

High yielding catenane synthesis? Surely not!

Lab-in-a-syringe approach to separating biomarkers from blood samples

Cheaper dye-sensitised solar cells

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