In chemistry, the nitro group (O-N=O) has a formidable reputation. The high reactivity that makes some nitro-bearing molecules potent explosives—think nitroglycerin or trinitrotoluene (TNT)—also enables NO2 to be extremely versatile in organic synthesis. Chemists can transform nitro groups into numerous other functionalities, such as biologically important amines or carbonyl compounds, providing a constant demand for new, efficient reactions involving these compounds.
Now, researchers led by Mikiko Sodeoka from the RIKEN Advanced Science Institute in Wako have developed an innovative way to connect organic molecules known as nitroalkenes and α-ketoesters together with precisely controlled geometries1. Because this synthesis uses an ‘environmentally friendly’ catalytic system, it can help create a broad range of molecules, including therapeutic natural products, under mild conditions.
Typically, reactions between nitroalkenes and α-ketoesters require hazardous liquids, generous quantities of catalysts, and very low temperatures to be successful. Instead, Sodeoka and her team were able to complete this chemical transformation at room temperature, with a non-toxic propanol solvent, by using small amounts of a nickel acetate catalyst —an advance with significant cost-saving and environmental-hazard reducing potential.
According to Yoshitaka Hamashima, a co-author of the paper, this discovery originated in the team’s previous finding that certain palladium complexes are stable and active catalysts, even in water2. After several trials, the researchers determined that nickel catalysts, which share similar properties to palladium materials, allowed the α-ketoesters to add to nitroalkenes with high yields and purity; over 90% of the final product corresponded to a specific stereoisomer, a molecule with a hard-to-achieve, geometrically distinct structure.
Hamashima explains that the nickel complexes are particularly effective because they recognize specific carbon atoms on the α-ketoesters and chemically activate them, generating products with precise frameworks. Furthermore, nickel has the right properties to maintain a delicate catalytic balance. “Nickel has a reasonable—not too strong, but not too weak—affinity towards nitro groups,” says Hamashima. “This affinity enabled the facile dissociation of the product from the catalyst, allowing high catalytic turnover.”
The high selectivity of this process, when combined with the mild reaction conditions, allowed the researchers to perform similar reactions on a broad range of molecules—including a highly efficient synthesis of the natural product kainic acid analog, a chemical that can bind to glutamate receptors within neuronal cells.
“Such selective activations are key to the success of our reaction,” says Hamashima. “Otherwise, undesired side reactions would occur when compounds with various functional groups are used as substrates.”
The corresponding author for this highlight is based at the Synthetic Organic Chemistry Laboratory, RIKEN Advanced Science Institute
Journal information1. Nakamura, A., Lectard, S., Hashizume, D., Hamashima, Y. & Sodeoka, M. Diastereo- and enantioselective conjugate addition of α-ketoesters to nitroalkenes catalyzed by a chiral Ni(OAc)2 complex under mild conditions. Journal of the American Chemical Society 132, 4036–4037 (2010)
2. Sodeoka, M. & Hamashima, Y. Chiral Pd aqua complex-catalyzed asymmetric C–C bond-forming reactions: a Brønsted acid–base cooperative system. Chemical Communications 5787–5798 (2009).
gro-pr | Research asia research news
Individual Receptors Caught at Work
19.10.2017 | Julius-Maximilians-Universität Würzburg
Rapid environmental change makes species more vulnerable to extinction
19.10.2017 | Universität Zürich
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.
It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...
17.10.2017 | Event News
10.10.2017 | Event News
10.10.2017 | Event News
19.10.2017 | Materials Sciences
19.10.2017 | Materials Sciences
19.10.2017 | Physics and Astronomy