Carbon dioxide has become notorious as a troublesome greenhouse gas produced by burning fossil fuels. Now, this gas could also offer a cheap, abundant and nontoxic source of carbon for the chemical reactions that synthesize products such as plastics and pharmaceuticals.
Only a few industrial processes currently use carbon dioxide as a reagent because it takes a lot of energy to break its strong chemical bonds. For example, to synthesize salicylic acid, a precursor of aspirin, carbon dioxide must be squeezed to 100 times atmospheric pressure and the reaction mixture heated to 125 ºC.
Hung Duong of the A*STAR Institute of Chemical and Engineering Sciences in Singapore and co-workers have shown that a copper catalyst can incorporate carbon dioxide into organic molecules under much milder conditions1. The commercially available catalyst consists of a copper atom joined to a bulky ligand called 1,3-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr).
Some reactions involving carbon dioxide require high-energy starting materials that contain reactive metals such as lithium or magnesium. However, these metals often destroy other sensitive chemical groups in the molecule during the reaction. Milder starting materials that contain tin tend to be highly toxic, “so we looked at the use of more environmentally benign organoborons,” says Duong.
The researchers tested a range of molecules that feature a carbon–carbon double bond close to a boron-containing chemical group. They assumed that the copper catalyst works by knocking the boron group off the molecule and briefly taking its place so that it can shepherd carbon dioxide into the right position to bond with the molecule. The products of the reaction contain a carbon–carbon double bond and a carboxylic acid group, arranged in a very predictable pattern. “These are highly versatile building blocks for organic synthesis,” explains Duong.
The reaction generally produced good yields of products when run at just 70 ºC and atmospheric pressure, although it was less successful in those cases where particularly large chemical groups were attached to one end of the starting material.
The reaction also needed relatively large amounts of catalyst – roughly one catalyst molecule for every 10 to 20 molecules of the starting material. “That amount is still too high for industrial use and needs further improvement,” says Duong.
His team now aims to expand the range of reactions that their catalyst can assist. “We are currently looking at exploiting the high reactivity of the copper catalyst toward carbon dioxide to prepare other valuable organic compounds under mild conditions,” he says.
The A*STAR-affiliated researchers contributing to this research are from the Institute of Chemical and Engineering Sciences.
Duong, H. A., Huleatt, P. B., Tan, Q.-W. & Shuying, E. L. Regioselective copper-catalyzed carboxylation of allylboronates with carbon dioxide. Organic Letters 15, 4034–4037, 2013.
MACC1 Gene Is an Independent Prognostic Biomarker for Survival in Klatskin Tumor Patients
31.08.2015 | Max-Delbrück-Centrum für Molekulare Medizin in der Helmholtz-Gemeinschaft
Fish Oil-Diet Benefits May be Mediated by Gut Microbes
28.08.2015 | University of Gothenburg
Longer, more severe, and hotter droughts and a myriad of other threats, including diseases and more extensive and severe wildfires, are threatening to transform some of the world's temperate forests, a new study published in Science has found. Without informed management, some forests could convert to shrublands or grasslands within the coming decades.
"While we have been trying to manage for resilience of 20th century conditions, we realize now that we must prepare for transformations and attempt to ease...
A University of Oklahoma astrophysicist and his Chinese collaborator have found two supermassive black holes in Markarian 231, the nearest quasar to Earth, using observations from NASA's Hubble Space Telescope.
The discovery of two supermassive black holes--one larger one and a second, smaller one--are evidence of a binary black hole and suggests that supermassive...
A team of European researchers have developed a model to simulate the impact of tsunamis generated by earthquakes and applied it to the Eastern Mediterranean. The results show how tsunami waves could hit and inundate coastal areas in southern Italy and Greece. The study is published today (27 August) in Ocean Science, an open access journal of the European Geosciences Union (EGU).
Though not as frequent as in the Pacific and Indian oceans, tsunamis also occur in the Mediterranean, mainly due to earthquakes generated when the African...
In mountainous regions earthquakes often cause strong landslides, which can be exacerbated by heavy rain. However, after an initial increase, the frequency of these mass wasting events, often enormous and dangerous, declines, in fact independently of meteorological events and aftershocks.
These new findings are presented by a German-Franco-Japanese team of geoscientists in the current issue of the journal Geology, under the lead of the GFZ...
Bacteria do not cease to amaze us with their survival strategies. A research team from the University of Basel's Biozentrum has now discovered how bacteria enter a sleep mode using a so-called FIC toxin. In the current issue of “Cell Reports”, the scientists describe the mechanism of action and also explain why their discovery provides new insights into the evolution of pathogens.
For many poisons there are antidotes which neutralize their toxic effect. Toxin-antitoxin systems in bacteria work in a similar manner: As long as a cell...
20.08.2015 | Event News
20.08.2015 | Event News
19.08.2015 | Event News
31.08.2015 | Awards Funding
31.08.2015 | Materials Sciences
31.08.2015 | Materials Sciences