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
Brought to light – chromobodies reveal changes in endogenous protein concentration in living cells
21.09.2018 | NMI Naturwissenschaftliches und Medizinisches Institut an der Universität Tübingen
A one-way street for salt
21.09.2018 | Julius-Maximilians-Universität Würzburg
The building blocks of matter in our universe were formed in the first 10 microseconds of its existence, according to the currently accepted scientific picture. After the Big Bang about 13.7 billion years ago, matter consisted mainly of quarks and gluons, two types of elementary particles whose interactions are governed by quantum chromodynamics (QCD), the theory of strong interaction. In the early universe, these particles moved (nearly) freely in a quark-gluon plasma.
This is a joint press release of University Muenster and Heidelberg as well as the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt.
Then, in a phase transition, they combined and formed hadrons, among them the building blocks of atomic nuclei, protons and neutrons. In the current issue of...
Thin-film solar cells made of crystalline silicon are inexpensive and achieve efficiencies of a good 14 percent. However, they could do even better if their shiny surfaces reflected less light. A team led by Prof. Christiane Becker from the Helmholtz-Zentrum Berlin (HZB) has now patented a sophisticated new solution to this problem.
"It is not enough simply to bring more light into the cell," says Christiane Becker. Such surface structures can even ultimately reduce the efficiency by...
A study in the journal Bulletin of Marine Science describes a new, blood-red species of octocoral found in Panama. The species in the genus Thesea was discovered in the threatened low-light reef environment on Hannibal Bank, 60 kilometers off mainland Pacific Panama, by researchers at the Smithsonian Tropical Research Institute in Panama (STRI) and the Centro de Investigación en Ciencias del Mar y Limnología (CIMAR) at the University of Costa Rica.
Scientists established the new species, Thesea dalioi, by comparing its physical traits, such as branch thickness and the bright red colony color, with the...
Scientists have succeeded in observing the first long-distance transfer of information in a magnetic group of materials known as antiferromagnets.
An international team of researchers has mapped Nemo's genome, providing the research community with an invaluable resource to decode the response of fish to...
21.09.2018 | Event News
03.09.2018 | Event News
27.08.2018 | Event News
21.09.2018 | Physics and Astronomy
21.09.2018 | Life Sciences
21.09.2018 | Event News