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Lanthanide replacement in organic synthesis

Scientists form the UK have performed the Luche-type reduction of α,β-unsaturated ketones in the presence calcium triflate.

The reduction of α,β-unsaturated ketones to synthesize allylic alcohols is commonly performed with sodium borohydride in the presence of cerium(III) chloride, otherwise known as the Luche reduction.  However, trivalent lanthanide salts pose several disadvantages.  They are very expensive, and although generally non-toxic, if administered intravenously they are significantly toxic.

However, in this work scientists from Imperial College London and Pfizer Ltd in Sandwich, led by Matthew Fuchter, developed a route to give allylic alcohols from α,β-unsaturated ketones using calcium triflate to replace cerium(III) chloride.  This procedure also accomplished the regioselective 1,2-reduction of challenging α,β-unsaturated ketones such as 2-cyclopentenone with very good selectivity, and is suitable for the stereoselective reduction of α,β-aziridinyl ketones.

This article is free to access until the 23rd July 2012!  Click on the link below to find out more…

Lanthanide replacement in organic synthesis: Luche-type reduction of α,β-unsaturated ketones in the presence of calcium triflate, Nina V. Forkel, David A. Henderson and Matthew J. Fuchter, Green Chem., 2012, DOI: 10.1039/C2GC35619H

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Effective synthesis of 2,5-disubstituted tetrahydrofurans from glycerol by catalytic alkylation of ketones, Magnus Rueping and Vilas B. Phapale, Green Chem., 2012, 14, 55-57

Environmentally benign metal triflate-catalyzed reductive cleavage of the C–O bond of acetals to ethers, Yin-Jie Zhang, Wissam Dayoub, Guo-Rong Chen and Marc Lemaire, Green Chem., 2011, 13, 2737-2742

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Faster removal of cigarette filters from the environment

Cigarette filters that have been inappropriately discarded are a major environmental problem, making up a large proportion of litter, as the filters themselves can take years to degrade. In a bid to tackle this, researchers in the US have developed a cigarette filter with accelerated degradation.

Raymond Robertson from the acetate business of Celanese Corporation, Narrows, Virginia, has been working with colleagues to develop a filter that contains a controlled-release organic acid to catalyse the hydrolysis of the filter material – cellulose acetate polymer. ‘Our work focuses on expediting the filter degradation back to cellulose and acetic acid using edible materials, such as citric acid and ascorbic acid (vitamin C), to help promote the filter degradation rate,’ he says. ‘Increasing the degradation rate decreases the filter persistence in the environment.’

The weak organic acid is encapsulated in the filter paper to protect it from premature degradation and to prevent a decrease in the product’s shelf life. Once the cigarette is used and discarded, environmental water (such as rainwater) breaches the protective layer. This releases the acid, which migrates into the filter, lowering the pH and triggering hydrolysis.

Zhenjiang Li from Nanjing University of Technology, China, comments: ‘It is a remarkable breakthrough in addressing the cigarette filter pollution.’ A researcher in the fields of green chemistry and polymers, Li is impressed with the results. ‘The team have combined simple chemistry with current industrial processes.’

For Robertson, future developments involve refining the technology to suit a variety of environments, such as developing a coating and release technology that can work in very wet conditions.

Reproduced from a Chemistry World story written by Rebecca Brodie

This article is free to access for 6 weeks!  Click on the link below to find out more…

Accelerated degradation of cellulose acetate cigarette filters using controlled-release acid catalysis, Raymond M. Robertson, William C. Thomas, Jitendrakumar N. Suthar and David M. Brown, Green Chem., 2012, DOI: 10.1039/C2GC16635F

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Meet our Authors – Andrew Abbott

Andrew Abbott is a Professor of Physical Chemistry and Head of the Department of Chemistry at the University of Leicester, UK.  His research is based on the design, fundamental studies and applications of ionic liquids and deep eutectic solvents.  Andy took a few moments to chat to Green Chemistry

Who or what initially inspired you to become a chemist?

As with most chemists, I can trace my career in Chemistry to my chemistry teacher at school, Mr David Peacock at Abbotsfield School, West London. He used to take us to all kinds of demonstration lectures and he was a great inspiration.

What has been the motivation behind your recent research?

My own research is in the area of sustainable solvents, particularly ionic liquids. I am interested in developing sustainable materials and we are focussing on metal deposition and dissolution which I feel are some of the most pressing issues in green chemistry. Reducing aqueous effluents of heavy metals are some of the most pressing issues because of the acute toxicity and large volumes of the processes. These are ubiquitous problems and all of the solutions tend to be end of pipe. Our approach is to use ionic media to avoid aqueous effluent. This also allows us to build in more energy efficient deposition processes. We have take a number of these to commercial scale. We produce our liquid systems with the catch phrase “benign by design”. We ensure that rather than looking for the perfect chemical system we start with the perfect environmental system and then tailor it to the application. Our work is also investigating novel starch based plastics building biodegradation in from the outset and attempting to modify to material to obtain the optimum mechanical properties.

What do you see as the main challenges facing research in this area?

The main challenge facing Green Chemistry is the conservative tendency in manufacturing which leads to small incremental change. The challenge from an academic point of view is retaining credibility for new technologies. We still tend to go in fads such as supercritical fluids or ionic liquids and see them as a panacea. Process design tends to be lacking from many approaches. There is also a tendency to claim that something is Green as if it is an absolute that can be achieved. We need to focus on relative improvements in green metrics.

Where do you see the field of Green Chemistry being in 5 or 10 years time?

One of the challenges in Green Chemistry over the next 10 years is retaining credibility and building successful case studies. It should be seen as a goal in all processes to improve the green metrics and it should be a key goal to develop simple criteria that are non-quantitative but are highly indicative of the relative improvements that a process makes over existing technology. A simple scale or traffic light scheme which quantified changes in key indicators such as the scale of the process, the relative change in the hazard, environmental impact, and the practicality of the methodology.

And finally…

If you could not be a scientist, but could be anything else, what would you be?

Chemistry was always my fallback position. I always wanted to be an artist and had it not been for my lack of talent I would have surely made it. Recently I fulfilled a personal challenge to combine both areas and I devised a public lecture on the chemists role in art entitled “From Test Tube to Turner” which I gave at Burlington House. Even in this lecture there is still some Green Chemistry where I discuss the chemists desire to remove toxic heavy metals from the artists palette.

A couple of Andy’s recent Green Chemistry articles are currently free to access until the 18th July 2012:

Salt modified starch: sustainable, recyclable plastics, Andrew P. Abbott, Andrew D. Ballantyne, Jesus Palenzuela Conde, Karl S. Ryder and William R. Wise, Green Chem., 2012, 14, 1302-1307

Processing of metals and metal oxides using ionic liquids, Andrew P. Abbott, Gero Frisch, Jennifer Hartley and Karl S. Ryder, Green Chem., 2011, 13, 471-481

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Elimination of the negative effect of nitrogen compounds by CO2–water in the hydrocracking of anthracene

Chinese scientists have developed an effective was to remove the negative effects of nitrogen compounds in the hydrocracking of anthracene.

Although there are moves towards utilizing oils from renewable resources, petroleum-based hydrocarbon fuels will still be used in the immediate future.  Hydrocracking of heavy oils is an important way to produce high-value liquid fuels due to the low H/C atomic ratio of the initial feedstock.  However, heavy oils contact considerable amounts of nitrogen compounds which have significant negative effects on the reaction, primarily due to poisoning of the catalysts.

In this work, scientists led by Buxing Han from the Institute of Chemistry, Chinese Academy of Sciences, Beijing, China, present an effect method to overcome the effects of nitrogen compounds on the hydrocracking reaction.  By investigating the effects of water and CO2 on the hydrocracking of anthracene, the team found that a water-CO2 mixture could eliminate the negative effects induced by the presence of nitrogen compounds and even enhance the efficiency of the reaction.  The authors believe this is due to the buffer system that is created between the nitrogen compounds-water-CO2.

This article is currently free to access until the 13th July 2012!  Click on the link below to find out more…

Elimination of the negative effect of nitrogen compounds by CO2–water in the hydrocracking of anthracene, Honglei Fan, Qian Wang, Jin Guo, Tao Jiang, Zhaofu Zhang, Guanying Yang and Buxing Han, Green Chem., 2012, DOI: 10.1039/C2GC35424A

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Water as an additive to enhance the ring opening of naphthalene, Qian Wang, Honglei Fan, Suxiang Wu, Zhaofu Zhang, Peng Zhang and Buxing Han, Green Chem., 2012, 14, 1152-1158

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Green Chemistry article in C&EN – Catalytic conversion of biomass using solvents derived from lignin

A recently published Green Chemistry article by Editorial Board member James Dumesic (University of Wisconsin-Madison, USA) and colleagues has just been featured in the latest issue of Chemical & Engineering News.

The paper reports the  use of depolymerised lignin as a solvent in the conversion of hemicellulose and cellulose biomass fractions into high value platform chemicals and transportation fuels via a catalytic process.  The use of lignin-derived alkylphenols as solvents in this process (carried out in a biphasic reactor) minimized side-reactions in the aqueous phase and enabled recycling of the mineral acid catalysts. 

This article is free to access for 2 weeks!  Click on the link below to find out more…

Catalytic conversion of biomass using solvents derived from lignin, Pooya Azadi, Ronald Carrasquillo-Flores, Yomaira J. Pagán-Torres, Elif I. Gürbüz, Ramin Farnood and James A. Dumesic, Green Chem., 2012, 14, 1573-1576

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“On water” direct Pd-catalysed C–H arylation of thiazolo[5,4-d]pyrimidine derivatives

Chinese scientists have developed a new method for synthesising 2-arylsubstituted thiazolo[5,4-d]pyrimidine derivatives under mild conditions.

2-Arylsubstituted thiazolo[5,4-d]pyrimidine derivatives are the main motif in many pharmacologically relevant compounds including Tie-2 inhibitors and immunosuppressive agents.  Given the interest in these compounds, finding a mild and effective route to synthesis them is important.  Existing methods involve the use of toxic reagents and harsh conditions which limit their applications.  In this work, Tu-Yan Li, Li-Ping Sun and colleagues from China Pharmaceutical University, Nanjing, China, have developed a procedure for the direct arylation of thiazolo[5,4-d]pyrimidine derivatives with aryl iodides.  They employ a combination of Pd(Ph3)4 and Ag2CO3 used exclusively in water at 60 °C, giving the products in good to excellent yields.

This article is free to access until the 6th July 2012!  Click on the link below to find out more…

“On water” direct Pd-catalysed C–H arylation of thiazolo[5,4-d]pyrimidine derivatives, Ye-Xiang Su, Ya-Hui Deng, Ting-Ting Ma, Yu-Yan Li and Li-Ping Sun, Green Chem., 2012, DOI: 10.1039/C2GC35399G

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Efficient and convenient C-3 functionalization of indoles through Ce(OAc)3/TBHP-mediated oxidative C–H bond activation in the presence of β-cyclodextrin, Yu Lin Hu, Hui Jiang and Ming Lu, Green Chem., 2011, 13, 3079-3087

Greener solvents for ruthenium and palladium-catalysed aromatic C–H bond functionalisation, Cedric Fischmeister and Henri Doucet, Green Chem., 2011, 13, 741-753

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Meet our Authors: Michael Meier

Michael Meier is a Professor at the Karlsruhe Institute of Technology (KIT), Germany.  His research interests are utilizing plant oil derived fatty acids and terpenes etc., to prepare (novel) monomers study their subsequent polymerisation to obtain a variety of renewable polymers.  Michael took a few moments away from his work to talk to Green Chemistry

Who or what initially inspired you to become a chemist?

I was certainly inspired to become a chemist by my high-school chemistry teacher. Apart from being a great teacher in the class room, he offered voluntary lab-courses (which are still uncommon in Germany at this stage of education) and I will never forget making my first batch of Aspirin there. Without his excellent introduction to chemistry, I would probably have chosen another subject to study. Thank you Mr. Stegmüller!

What was the motivation behind the research described in your recent Green Chemistry article?

As for all research we do, our motivation is to find sustainable alternatives to existing chemistry. More importantly, we focus on a feedstock-shift from fossil resources to renewable ones. In our latest contribution, we used organocatalysis to develop new efficient procedures for the synthesis of organic carbonates and renewable polycarbonates. Catalysis is one aspect of the sustainability of this approach, but probably more important is the use of dimethyl carbonate as a non-toxic and potentially renewable alternative to phosgene for these reactions.

What do you see as the main challenges facing research in this area?

In my opinion, a major challenge will be the implementation of all the new and exciting findings that are described in the context of Green Chemistry into the chemical industry. Only then will chemistry have a chance to actually contribute to a sustainable development of our future. This is certainly one of my goals. In order to reach this, in my opinion chemistry does not only have to be sustainable, but also simple, broadly applicable and robust.

Where do you see the field of Green Chemistry being in 5 or 10 years time?

The field will definitely keep on growing. More and more research groups are joining the field, the younger generation is more aware of ecological problems and sustainability in general, and also industry has learned that sustainability often goes along with cost-savings. I thus look forward to a bright future of the field that will hopefully see many paradigm-changing and stimulating new results.

If you could not be a scientist, but could be anything else, what would you be?

If I would not be a scientist, I would probably run a coffee shop with the best cappuccino in town and homemade (organic of course) bagels and cakes. I actually thought about this option during my studies in Regensburg, because back then coffee-shops basically did not exist in Germany. But as you can guess from reading this, chemistry has won.

A couple of Michael’s recent Green Chemistry articles are currently free to access until the 2nd July 2012:

TBD catalysis with dimethyl carbonate: a fruitful and sustainable alliance, Hatice Mutlu, Johal Ruiz, Susanne C. Solleder and Michael A. R. Meier, Green Chem., 2012, 14, 1728-1735

Thiol-ene vs. ADMET: a complementary approach to fatty acid-based biodegradable polymers, Oĝuz Türünç and Michael A. R. Meier, Green Chem., 2011, 13, 314-320

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Encaged palladium catalyst for Suzuki-Miyaura cross-coupling reaction in aqueous media

Encaging the complex PdCl2(py)2 gave a highly efficient and reusable catalyst for the Suzuki-Miyaura cross-coupling reaction.

Tao Li and colleagues from Huazhong University of Science and Technology, China, successfully encaged the PdCl2(py)2 complex in the interior space of hollow silicate-1 spheres.  This new material was then applied to the Suzuki-Miyaura cross-coupling reaction of various aryl halides and arylboronic acids in aqueous media.  Even at Pd loadings of 0.0188 mol%, the catalyst gave fast conversions to the desired products under mild conditions.  Notably, due to the ‘anti-leaching’ effect of the zeolitic shell surrounding the Pd species, the catalyst showed excellent stability and reusability and could be reused 10 times without any appreciable loss of activity. 

This article is free to access until the 29th June 2012!  Click on the link below to find out more…

PdCl2(py)2encaged in monodispersed zeolitic hollow spheres: a highly efficient and reusable catalyst for Suzuki–Miyaura cross-coupling reaction in aqueous media, Zhenhong Guan, Jianglin Hu, Yanlong Gu, Haojun Zhang, Guangxing Li and Tao Li, Green Chem., 2012, DOI: 10.1039/C2GC35302D

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Heterogeneous catalytic synthesis using microreactor technology, Christopher G. Frost and Lynsey Mutton, Green Chem., 2010, 12, 1687-1703

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Green Chemistry issue 6 – now online!

The latest issue of Green Chemistry is now available online.

The front cover of this issue features work by João Coutinho and colleagues from the University of Aveiro, Portugal, who report investigations into the activity of the commercial enzyme Candida antarctica lipase B (CaLB) in aqueous solutions of ionic liquid.  The group observed that it was possible to induce superactivity in CaLB by using a long chain ionic liquid, 1-decyl-3-methylimidazolium chloride.  This increase in activity did not result from changes in the reaction mechanism or in the structure of the enzyme induced by the ionic liquid.  Instead, this phenomenon may be explained by the formation of microemulsions due to self-aggregation of the ionic liquid chain. 

Ionic liquids microemulsions: the key to Candida antarcticalipase B superactivity, Sónia P. M. Ventura, Luísa D. F. Santos, Jorge A. Saraiva and João A. P. Coutinho, Green Chem., 2012, 14, 1620-1625

The inside front cover of this issue highlights work by Alexis Bell and colleagues from the University of California, Berkeley, USA, who have developed a low energy intensive process for the production of diesel fuels from 5-(hydroxymethyl)furfural (HMF) and D-(–)-fructose.  Alcoholic solutions of these chemicals in the presence of solid acid catalysts produced a variety of potential bio-diesel candidates, with Amberlyst-15 and Dowex DR2030 catalysts showing exceptional reactivity and selectivity.  The distribution of products could be altered by varying the reaction conditions, i.e.by raising or lowering the reaction temperature.  Metal catalysed hydrogenation of HMF using platinum gave exclusive selectivity for reduction of the carbonyl functionality of HMF. 

Etherification and reductive etherification of 5-(hydroxymethyl)furfural: 5-(alkoxymethyl)furfurals and 2,5-bis(alkoxymethyl)furans as potential bio-diesel candidates, Madhesan Balakrishnan, Eric R. Sacia and Alexis T. Bell, Green Chem., 2012, 14, 1626-1634

These articles are free to access for 6 weeks!

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Membrane technologies in sustainable chemistry

Membranes and membrane technologies are quickly finding applications in sustainable chemical processes.  These range from easy separation of products from reaction mixtures and purification of solvents, to the recovery of reagents or catalysts from reaction mixtures for reuse. 

Green Chemistry is an excellent forum for work in this field and a selection of recent high quality articles has been collated below.  These articles are all free to access until the 25th June 2012, so why not take a look…

Keep up-to-date with the latest reviews and primary research in this field by registering for our e-alerts today!

High performance membranes based on ionic liquid polymers for CO2 separation from the flue gas, Pei Li, D. R. Paul and Tai-Shung Chung, Green Chem., 2012, 14, 1052-1063

Direct transformation of ethanol into ethyl acetate through catalytic membranes containing Pd or Pd-Zn: comparison with conventional supported catalysts, Adriana Bonilla Sánchez, Narcís Homs, Sylvain Miachon, Jean-Alain Dalmon, José Luis G. Fierro and Pilar Ramírez de la Piscina, Green Chem., 2011, 13, 2569-2575

Enzyme immobilization on/in polymeric membranes: status, challenges and perspectives in biocatalytic membrane reactors (BMRs), Peter Jochems, Yamini Satyawali, Ludo Diels and Winnie Dejonghe, Green Chem., 2011, 13, 1609-1623

Environmentally friendly route for the preparation of solvent resistant polyimide nanofiltration membranes, Iwona Soroko, Yogesh Bhole and Andrew Guy Livingston, Green Chem., 2011, 13, 162-168

Continuous biocatalytic synthesis of (R)-2-octanol with integrated product separation, Christina Kohlmann, Susanne Leuchs, Lasse Greiner and Walter Leitner, Green Chem., 2011, 13, 1430-1436

Sustainable recovery of pure natural vanillin from fermentation media in a single pervaporation step, Carla Brazinha, Dalje S. Barbosa and João G. Crespo, Green Chem., 2011, 13, 2197-2203

Recent advances in the recycling of homogeneous catalysts using membrane separation, Michèle Janssen, Christian Müller and Dieter Vogt, Green Chem., 2011, 13, 2247-2257

Performance of solvent resistant nanofiltration membranes for purification of residual solvent in the pharmaceutical industry: experiments and simulation, Siavash Darvishmanesh, Loghman Firoozpour, Johan Vanneste, Patricia Luis, Jan Degrève and Bart Van der Bruggen, Green Chem., 2011, 13, 3476-3483

Challenges for recycling ionic liquids by using pressure driven membrane processes, Kurt Haerens, Stephanie Van Deuren, Edward Matthijs and Bart Van der Bruggen, Green Chem., 2010, 12, 2182-2188

Product recovery from ionic liquids by solvent-resistant nanofiltration: application to ozonation of acetals and methyl oleate, Charlie Van Doorslaer, Daan Glas, Annelies Peeters, Angels Cano Odena, Ivo Vankelecom, Koen Binnemans, Pascal Mertens and Dirk De Vos, Green Chem., 2010, 12, 1726-1733

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