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Japan's Revolutionary Achievements
in Organic Synthesis

Cross-Coupling Reactions Win Nobel Prizes for Japanese Chemists

Dr. Negishi Ei-ichi

Dr. Negishi Ei-ichi (C)Purdue University photo

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Liquid crystals are all around us today, crucial components in everyday high-tech equipment like televisions, cell phones, and computer monitors. Japanese breakthroughs in the field of organic chemistry have been indispensable in making it possible to produce these materials on an industrial scale. In 2010, two Japanese scientists won Nobel Prizes in Chemistry for their work in the field of cross-coupling reactions.

A cross-coupling is a chemical reaction that makes it possible to join carbon atoms together to form new organic compounds, leading to revolutionary new materials in pharmaceuticals and electronics.

Dr. Suzuki Akira

Dr. Suzuki Akira

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Japanese Breakthroughs in Organic ChemistryCarbon atoms do not react easily with one another, and scientists need to render carbon more reactive in order to bind carbon atoms together. Traditional methods worked with simple molecules, but attempts to make more complex molecules with these methods resulted in unwanted by-products. A major breakthrough came in 1977 when Dr. Negishi Ei-ichi, professor of chemistry at Purdue University in the United States, achieved a cross-coupling using a palladium catalyst. This type of reaction, now known as a Negishi Cross-Coupling in his honor, has since been used with a variety of different metals, including zinc, aluminum, and zirconium.

Another Japanese chemist, Dr. Suzuki Akira of Hokkaido University, further expanded the potential of cross-coupling reactions. The "Suzuki-Miyaura Coupling" first published in 1979, improved the stability of the synthesis reaction by using an organic boron-containing compound. By producing a stable reaction and fewer byproducts, this reaction made it possible for non-specialists to work with cross-coupling reactions for the first time.

Organic EL illumination panels

Organic EL illumination panels (C) Panasonic Electric Works Prototype organic EL illumination panels

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The Japanese Technology in Your TV and PhoneThe liquid crystals used in the latest television and cell phone displays are perhaps the best-known industrial application of the Suzuki-Miyaura Coupling. Liquid crystals are unique organic compounds combining the properties of conventional liquids and solid crystals. Since liquid crystal displays (LCD) appeared in the 1990s, researchers have been working to develop new materials capable of offering even sharper images and even thinner screens. Suzuki-Miyaura couplings are vital for producing these materials.

A cell phone display

A cell phone display incorporating organic EL technology

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The Suzuki-Miyaura Coupling is also essential to the production of organic EL, which experts believe will become the main source material for the next generation of flat-panel displays. Organic EL consists of organic compounds that emit light in response to an electric current. The complex structure of the light-emitting part of the organic compound is produced by an organic synthesis using a Suzuki-Miyaura Coupling. Researchers are working to make a commercially viable version of the technology for use in products such as ultra-thin lighting equipment.

One reason that cross-coupling reactions have become so widespread is that neither Negishi nor Suzuki has sought patents for their discovery. Developed by Japanese scientists and used by engineers and developers around the world, cross-coupling reactions will continue to play a vital role on the frontline of cutting-edge technology for the foreseeable future.(March 2011)

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