Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Economizing chemistry, atom by atom

06.02.2012
Industrial chemistry is set to improve from novel rare-earth metal catalysts that reduce waste and improve aromatic bond-forming reactions

In chemistry, downsizing can have positive attributes. Reducing the number of steps and reagents in synthetic reactions, for example, enables chemists to boost their productivity while reducing their environmental footprint. This type of ‘atom economy’ could soon improve, thanks to a new rare-earth metal catalyst developed by Zhaomin Hou and colleagues at the RIKEN Advanced Science Institute, Wako1. Their catalyst makes it simpler to modify aromatic carbon–hydrogen (C–H) bonds with silicon-bearing silyl ligands—a reaction step critical to pharmaceutical and materials science manufacturers alike.

Silicon, which is less electronegative than carbon or hydrogen atoms, can significantly alter the electronic characteristics of an organic molecule. Replacing the hydrogen atoms of an aromatic C–H group with silyl groups has emerged as an important strategy in industrial-scale chemical synthesis because these substituents can tune molecular reactivity, enabling construction of elaborate chemical frameworks.

Chemists normally use transition metals such as platinum or rhodium to catalyze aromatic silylation reactions. But to achieve high conversions, these catalysts need to be mixed with additional hydrogen acceptor reagents, which can generate unwanted waste products, including alkanes.

Hou and colleagues have pioneered studies into rare-earth metals, such as scandium, which have different catalytic properties to transition metals. Recently, they found that ‘half-sandwich’ scandium complexes, bonded on one side by a flat organic ring, showed unique activity and selectivity in the presence of carbon double bonds2. This made investigations of unsaturated aromatic molecules a natural next step.

When the researchers mixed a methoxy–benzene compound called anisole with the half-sandwich scandium catalyst and a phenylsilane, they found that the silyl group substituted onto the aromatic ring with excellent selectivity and yields (Fig. 1). Furthermore, the catalyst did not require hydrogen acceptor reagents, and generated only H2 gas as a by-product. Hou notes that this reaction is highly advantageous in terms of atom economy.

X-ray and spectroscopic measurements revealed that the working form of the catalyst, which contained a pair of ‘bridging’ hydrogen atoms, activated the reaction by coordinating the anisole’s methoxy group to the rare-earth metal. According to Hou, this relatively strong interaction directs silylation to occur almost exclusively at the position adjacent to the methoxy unit on the aromatic ring—a ‘regioselectivity’ that outshines that of transition metal catalysts, whose weak oxygen–metal interactions often produce an undesirable mix of silylation isomers.

The team will continue to explore new approaches to improving catalytic sustainability and selectivity by tapping into the extraordinary properties of rare-earth metals.

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

gro-pr | Research asia research news
Further information:
http://www.riken.jp
http://www.researchsea.com

More articles from Life Sciences:

nachricht Molecular motors run in unison in a metal-organic framework
20.03.2019 | University of Groningen

nachricht Active substance from plant slows down aggressive eye cancer
20.03.2019 | Rheinische Friedrich-Wilhelms-Universität Bonn

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Self-healing coating made of corn starch makes small scratches disappear through heat

Due to the special arrangement of its molecules, a new coating made of corn starch is able to repair small scratches by itself through heat: The cross-linking via ring-shaped molecules makes the material mobile, so that it compensates for the scratches and these disappear again.

Superficial micro-scratches on the car body or on other high-gloss surfaces are harmless, but annoying. Especially in the luxury segment such surfaces are...

Im Focus: Stellar cartography

The Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) in Arizona released its first image of the surface magnetic field of another star. In a paper in the European journal Astronomy & Astrophysics, the PEPSI team presents a Zeeman- Doppler-Image of the surface of the magnetically active star II Pegasi.

A special technique allows astronomers to resolve the surfaces of faraway stars. Those are otherwise only seen as point sources, even in the largest telescopes...

Im Focus: Heading towards a tsunami of light

Researchers at Chalmers University of Technology and the University of Gothenburg, Sweden, have proposed a way to create a completely new source of radiation. Ultra-intense light pulses consist of the motion of a single wave and can be described as a tsunami of light. The strong wave can be used to study interactions between matter and light in a unique way. Their research is now published in the scientific journal Physical Review Letters.

"This source of radiation lets us look at reality through a new angle - it is like twisting a mirror and discovering something completely different," says...

Im Focus: Revealing the secret of the vacuum for the first time

New research group at the University of Jena combines theory and experiment to demonstrate for the first time certain physical processes in a quantum vacuum

For most people, a vacuum is an empty space. Quantum physics, on the other hand, assumes that even in this lowest-energy state, particles and antiparticles...

Im Focus: Sussex scientists one step closer to a clock that could replace GPS and Galileo

Physicists in the EPic Lab at University of Sussex make crucial development in global race to develop a portable atomic clock

Scientists in the Emergent Photonics Lab (EPic Lab) at the University of Sussex have made a breakthrough to a crucial element of an atomic clock - devices...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

International Modelica Conference with 330 visitors from 21 countries at OTH Regensburg

11.03.2019 | Event News

Selection Completed: 580 Young Scientists from 88 Countries at the Lindau Nobel Laureate Meeting

01.03.2019 | Event News

LightMAT 2019 – 3rd International Conference on Light Materials – Science and Technology

28.02.2019 | Event News

 
Latest News

Molecular motors run in unison in a metal-organic framework

20.03.2019 | Life Sciences

Active substance from plant slows down aggressive eye cancer

20.03.2019 | Life Sciences

Novel sensor system improves reliability of high-temperature humidity measurements

20.03.2019 | Trade Fair News

VideoLinks
Science & Research
Overview of more VideoLinks >>>