Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

From pollution to solution

06.12.2010
‘Green’ catalysts transform carbon dioxide gas into valuable building blocks for organic synthesis

Chemists are helping to reduce heat-trapping carbon dioxide (CO2) emissions, which are a global concern. For example, they are devising new catalytic systems that would enable waste CO2 to be recycled as a non-toxic and practically free source of carbon for organic synthetic reactions. However, current CO2 conversion techniques require expensive metal catalysts or drawn-out procedures.

Now, Zhaomin Hou and colleagues from the RIKEN Advanced Science Institute in Wako have found a way to insert CO2 directly into the framework of aromatic molecules, turning them into carboxylic acid derivatives that are widely used as pharmaceuticals, agrichemicals, and dyes1. Importantly, this transformation can be achieved economically and with negligible environmental impact, thanks to a low cost copper complex bearing an organic ligand.

N-heterocyclic carbenes (NHCs) are molecules with near metal-like reactivity because of an electron-deficient carbon center. For the past two decades, scientists have used NHCs as organic replacements for metal catalysts and as ‘spectator’ ligands that attach to metal centers and influence their catalytic behavior. Hou and colleagues recently discovered that adding NHCs to copper, one of the most abundant metals in nature, created a complex that catalyzed CO2 addition to boron esters2—a trick the team hoped to repeat with aromatic hydrocarbons.

The most efficient way to incorporate CO2 into benzene-like molecules is by replacing one of the carbon–hydrogen (C–H) bonds on the outer ring; unfortunately, these bonds are notoriously unreactive. To overcome this problem, the researchers turned to benzoxazole: this double-ringed aromatic compound has a C–H bond situated between nitrogen and oxygen atoms, making it easier to chemically activate this position.

With just a pinch of the NHC–copper catalyst complex, the team found they could convert a mixture of CO2 and several different benzoxazole-based molecules into solid carboxylic acids and esters in excellent yields (Fig. 1). Carefully characterizing the crystal structures of several intermediate compounds revealed that CO2 inserted in between a copper–carbon bond formed at the benzoxazole C–H site, followed by a dissociation step that regenerated the catalyst.

According to Hou, the NHC ligand was essential in enabling CO2 capture. “The electron-donating ability of NHC could make the C–H activation and CO2 insertion steps easier, while its steric bulk brings stability to the active catalyst species,” he notes. The researchers now hope to extend this technique to less reactive C–H bonds by fine-tuning the catalyst complex and optimizing reaction conditions.

The corresponding author for this highlight is based at the Organometallic Chemistry Laboratory, RIKEN Advanced Science Institute

Journal information
1. Zhang, L., Cheng, J., Ohishi, T. & Hou, Z. Copper-catalyzed direct carboxylation of C–H bonds with carbon dioxide. Angewandte Chemie International Edition 49, 8670–8673 (2010). article

2. Ohishi, T., Nishiura, M. & Hou, Z. Carboxylation of organoboronic esters catalyzed by N-heterocyclic carbene copper(I) complexes. Angewandte Chemie International Edition 47, 5792–5795 (2008).

gro-pr | Research asia research news
Further information:
http://www.researchsea.com/html/article.php/eml/1/aid/5677/cid/1

More articles from Life Sciences:

nachricht Multi-institutional collaboration uncovers how molecular machines assemble
02.12.2016 | Salk Institute

nachricht Fertilized egg cells trigger and monitor loss of sperm’s epigenetic memory
02.12.2016 | IMBA - Institut für Molekulare Biotechnologie der Österreichischen Akademie der Wissenschaften GmbH

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

Im Focus: Fraunhofer ISE Develops Highly Compact, High Frequency DC/DC Converter for Aviation

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

UTSA study describes new minimally invasive device to treat cancer and other illnesses

02.12.2016 | Medical Engineering

Plasma-zapping process could yield trans fat-free soybean oil product

02.12.2016 | Agricultural and Forestry Science

What do Netflix, Google and planetary systems have in common?

02.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>