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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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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.

You can also follow your favourite publications on twitter and sign up to the e-alert service!

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Yong-Qiang Tu joins the ChemComm Editorial Board

30 Jul 2012

On behalf of the ChemComm Editorial Board, I am delighted to welcome Professor Yong-Qiang Tu as the new ChemComm Associate Editor for organic chemistry.

Professor Tu is a council member of Chinese Chemistry Society and the president of Gansu Chemistry Society. His current research interests centre on tandem rearrangement reactions and their application to the total syntheses of bioactive alkaloids, synthetic studies of biologically active natural products, and the construction of C-C and C-N bonds via C-H functionalisations.

Professor Tu’s editorial office is now open for submissions, welcoming urgent communications highlighting the latest advances in organic chemistry.

Find out more about Professor Tu’s research by reading these exciting articles:

Total synthesis of (±)-maistemonine and (±)-stemonamide
Zhi-Hua Chen, Yong-Qiang Zhang, Zhi-Min Chen, Yong-Qiang Tu and Fu-Min Zhang
Chem. Commun., 2011,47, 1836-1838, DOI: 10.1039/C0CC02612C, Communication

Enantioselective bromination/semipinacol rearrangement for the synthesis of β-bromoketones containing an all-α-carbon quaternary center
Hui Li , Fu-Min Zhang , Yong-Qiang Tu , Qing-Wei Zhang , Zhi-Min Chen , Zhi-Hua Chen and Jian Li
Chem. Sci., 2011,2, 1839-1841, DOI: 10.1039/C1SC00295C

Are you an organic chemist based in North America? Submit your research to Michael Krische, ChemComm North American Associate Editor for organic chemistry.

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Quick and clean way to make intermediates for dyes and pharmaceuticals

30 Jul 2012

Scientists in China have developed a quick and clean way to reduce nitroarenes to aminoarenes, which are common intermediates for making dyestuffs, pharmaceuticals and agricultural chemicals.

Sodium borohydride and molecular hydrogen are commonly used for this reaction but their hydrogen elements cannot reduce nitroarenes under mild reaction conditions. Usually, expensive noble-metal catalysts are necessary to activate the hydrogen elements in the reductants.

Here, the researchers have used a vanadium-doped porous TiO₂ with highly active hydrogen, which can instantly (<10s) and selectively reduce nitroarenes to aminoarenes under ambient conditions without catalysts. After being consumed by nitroarenes, the active hydrogen species can be regenerated by irradiating the V-doped TiO₂ with UV light.

Link to journal article
Porous vanadium-doped titania with active hydrogen: a renewable reductant for chemoselective hydrogenation of nitroarenes at ambient condition
J Su et al
Chem. Commun., 2012, DOI: 10.1039/c2cc33969b

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Film to aid drug metabolism study

05 Jul 2012

A way to study drug metabolism using cytochrome P450 enzymes (which are involved in the metabolism of over 60% of clinically used drugs) has been developed by scientists in China.

The team made a film of indium tin oxide nanoparticles (they have good conductivity) and cytochrome P450s encapsulated by chitosan (which are biocompatible) on a carbon electrode. They were able to bioelectronically initiate cytochrome P450 catalysis by replacing electron donation from expensive nicotinamide adenine dinucleotide phosphate with electrodes.

The system has potential for applications in drug discovery and development by monitoring substrate metabolism and enzyme inhibition. Other applications include biosensors for toxicity analysis and bioreactors for chemical synthesis.

Link to journal article
Electrochemically Driven Drug Metabolism via Cytochrome P450 2C9 Isozyme Microsomes with Cytochrome P450 Reductase and Indium Tin Oxide Nanoparticle Composites
X Xu et al
Chem. Commun., 2012, DOI: 10.1039/c2cc33575a

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Deadline Approaching – ICPOC 21 poster abstracts

29 Jun 2012

There is still just time to submit your poster abstract to the 21st IUPAC International Conference on Physical Organic Chemistry (ICPOC 21) but don’t delay.

The deadline date of 13 July is for both poster abstracts and early bird registrations.

Why join ICPOC21?

Professor Hiromitsu Maeda, Ritsumeikan University, Japan has won the 2012 ChemComm Emerging Investigator Lectureship and will delivering his lecture at ICPOC 21.

This annual award recognises an emerging scientist in the early stages of their independent academic career. Professor Maeda’s has been particularly commended for his contributions to the fields of organic chemistry, supramolecular chemistry and materials science.

In addition to the outstanding plenary sessions, there will be three parallel sessions over the five days comprising invited lectures and contributed talks, as well as poster sessions.

A broad range of scientists from across the whole community who share a quantitative perspective on chemistry will be there, providing an opportunity to discuss and celebrate the current status, development, and the future of physical organic chemistry.

Make sure you are one of them! Don’t miss the poster abstract submission and early bird registration deadline – 13 July.

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A new catalyst for asymmetric aziridination

26 Jun 2012

Aziridines are used extensively as intermediates for organic synthesis. The strained three-membered heterocycles reveal amino groups on ring-opening and therefore provide access to a variety of useful products. Enantioselective methods for forming aziridine rings are highly desirable because enantiopure amino-compounds represent important targets for both natural product synthesis and in the discovery of novel therapeutics.

Researchers from Kyushu University in Japan have reported a newly designed Ru(CO)salen complex (4), which acts as an efficient catalyst for asymmetric aziridination of alkenes.

Reaction of olefinic substrates (1) with 2-(trimethylsilyl)ethanesulfonyl (SES) protected azide (2) in the presence of the Ru(CO)salen complex 4 afforded enantioenriched aziridine products. 4 efficiently decomposes azides under ambient conditions and also catalyses asymmetric aziridination.

Judicious selection of an appropriate azide protecting-group also influenced the design of the catalyst. The researchers chose to include an appropriately located C–F bond within the ligand in order to improve tolerance of 4 to reacting electrophiles.

Low catalyst loadings enabled the highly enantioselective azirdination of a variety of substrates possessing conjugated or non-conjugated terminal or cyclic olefins.

Find out more – download the communication for free for a limited period.

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Additional benefit of cancer drug

21 Jun 2012

A new clinically used cancer drug thought to work by inhibiting kinase enzymes also strongly inhibits carbonic anhydrase (CA) enzymes, reveal scientists in Italy.

Scientists did not evaluate the CA inhibition activity of pazopanib before its approval for the treatment of a variety of different cancers, including lung, breast and ovarian cancers. But Claudiu Supuran and colleagues recognised part of the drug’s structure – a primary sulfonamide moiety – is often found in drugs that can inhibit CAs. So they tested pazopanib along with some other related structures and found that the drug did indeed inhibit CAs. They estimate that a significant proportion of the drug’s therapeutic effect on hypoxic tumors is due to its strong CA inhibitory properties.

Link to journal article
Polypharmacology of sulfonamides: Pazopanib, a multitargeted receptor tyrosine kinase inhibitor in clinical use, potently inhibits several mammalian carbonic anhydrases
J-Y Winum et al
Chem. Commun., 2012, DOI: 10.1039/c2cc33415a

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Outstanding organocatalysis – An article collection

13 Jun 2012

Catalysts are key to some of the most important reactions on the planet; a world without the Haber process or catalysts to crack crude oil is difficult to imagine. Not to mention the enzymatic reactions that are crucial to all life on earth.

Organocatalysts are an important class of catalyst and consist of carbon-based molecules often functionalised with oxygen, sulfur, nitrogen or phosphorus. They have shown promise in a range of reactions including hydrogenation, Diels-Alder, Michael and Mannich reactions, and are of particular interest in asymmetric reactions.

To help keep you up-to-date with the latest in cutting-edge organocatalytic research we have made the following articles free to access until 9^th July. After reading all these there will be little you won’t know about the exciting world of organocatalysis!

Click here for the full list of free articles

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Chiral Control for the Future?

24 May 2012

Tragedies such as the thalidomide scandal led to a re-think as to how pharmaceutical drugs are tested and examined before their sale to the public. Prior to this, racemic mixtures were often administered yet sometimes only one enantiomer of the compound gave the therapeutic properties while the other caused serious side effects. For this reason, huge interest developed in controlling reactions so that only enantiomer would be formed – not a trivial task for the many millions of molecules tumbling around in a round bottom flask! Such is the significance of this problem that the 2001 Nobel Prize for Chemistry was awarded to Sharpless, Noyori and Knowles for work in this field.

: Figure 1: Preparation of chiral-at-copper complexes

Many of the methods to obtain this selectivity focus on controlling the orientation of the molecule by building a bulky pocket around the reaction site. Doing so means a reaction can only occur on one side and, as a result, only one enantiomer is created. While this technique has been shown to work well, an alternative approach is to create a reaction site which itself can control the orientation of the molecule. It is exactly this that Paul Newman, Kingsley Cavell and Benson Kariuki at Cardiff University have achieved.

The idea behind the concept is that the reaction site itself is a more efficient way of transferring the control of the chirality. To do this they have created a ‘chiral-at-metal’ Cu(I) complex (Figure 1) which is itself very rare due to the instability of these types of compounds. The characterisation of such an exciting complex is certainly worthy of rapid communication but I hope to see further papers on this work in the near future, giving us an insight into how well this complex performs as a catalyst and how effective it is at transferring chirality. Over time, the catalyst will surely undergo many subtle alterations to improve its performance but only time will tell if this is truly going to be the most effective method of controlling chirality.

Keen to read more? Download this ChemComm article here.

Posted on behalf of Ruaraidh McIntosh, Chemical Communications web writer.

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