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.
Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides
16.07.2018 | Tokyo Institute of Technology
The secret sulfate code that lets the bad Tau in
16.07.2018 | American Society for Biochemistry and Molecular Biology
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
16.07.2018 | Life Sciences
16.07.2018 | Earth Sciences
16.07.2018 | Physics and Astronomy