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Capture serendipity!
- Curiosity and broad perspective lead to the Nobel Prize

Takanori Shibata
Professor, Faculty of Science and Engineering, Waseda University

The 2010 Nobel Prize in Chemistry was awarded jointly to Richard F. Heck, Professor Emeritus at the University of Delaware, USA, Ei-ichi Negishi, Distinguished Professor at Purdue University, USA, and Akira Suzuki, Professor Emeritus at Hokkaido University, Japan for their accomplishments in "palladium-catalyzed cross couplings in organic synthesis." This brings the total number of Japanese Nobel laureates to 18, including 15 in the field of natural science, and the spate of 9 winners in the last decade in particular has bolstered Japan's reputation as a science-based nation.

It is no exaggeration to say that organic compounds are what sustain our modern lives. From the liquid crystal used in our mobile phones and televisions to the drugs that help us survive and the agricultural chemicals that provide stable food supplies to prevent human famine, all are composed of organic compounds which are mainly composed of a framework of carbon atoms. If we can freely synthesize new organic compounds with a desired molecular structure-as we would freely paint a picture on a canvas-our lives may be further enriched. With this background in mind, I would like to introduce the achievements of Negishi and Suzuki.

The primary raw material of organic compounds is petroleum, which is a mixture of hydrocarbon compounds consisting of carbon and hydrogen atoms. However, hydrocarbon compounds are usually extremely stable and have poor reactivity, however, so the reaction between hydrocarbon compounds scarcely proceeds. To increase their reactivity, Negishi introduced zinc or aluminum to hydrocarbon compounds, and Suzuki used boron. Bromine or iodine was introduced to the hydrocarbon compound as a counterpart. Then, through the addition of palladium as a mediator of the reaction, a bond forms between the organozinc, organoaluminum or organoboron compound and the brominated or iodinated compound. Organoaluminum compounds are unstable in water and under an oxygen atmosphere, and these reactions require moisture and an oxygen-free environment.

Boron, on the other hand, is a relatively abundant element in the world, and organoborons are stable, so the reactions can proceed even in water. Suzuki coupling therefore is more practical-because the raw materials are cheap, and the reactions can be performed with simpler apparatus-and the process including Suzuki coupling is used for the mass production of the hypertension drug valsartan, the disinfectant boscalid, and the like. Although palladium, a precious metal, is expensive, it works as a catalyst which repeatedly mediates the reaction between two compounds, and therefore, only a very small amount (in terms of the number of molecules, about one palladium per 100 to 1000 organic compounds) is needed for the effective coupling. Another feature of Suzuki cross coupling is that the reactivity of organic compounds was moderately increased by the introduction of boron, and palladium facilitates the reaction. If the reactivity is sufficiently high to react without the aid of palladium, undesired reactions may also proceed to give a complex mixture. In other words, the combination of boron and palladium is ideal for the selective formation of the desired carbon-carbon bond.

Cross coupling is a fascinating method for the carbon-carbon bond formation. In fact, many Japanese organic chemists contributed to the success of this field in around 1970. Examples include the palladium-catalyzed Tsuji-Trost reaction, the nickel-catalyzed Kumada-Tamao-Corriu coupling, and too many others to mention here. In particular, we should keep in mind that, one year before the new Nobel laureate Heck published his results, the late Mr. Mizoroki at the Tokyo Institute of Technology disclosed his research, which included almost the same concept as Heck's.

We organic chemists examined many experiments every day, day and night. It is not that we mix chemicals together haphazardly like the old-time dubious alchemists did. We combine wisdom with originality to envisage new reactions based on theoretical backgrounds, and then we actually mix chemicals in a flask. If the reaction proceeds as expected, we are surely delighted because our idea proves to be correct, but we are even much more delighted when unexpected and intriguing reactions occur. Following on from 2000 and 2002 Nobel laureates Hideki Shirakawa and Koichi Tanaka, this year's winner Akira Suzuki has also mentioned the importance of serendipity. There are two essential points for taking advantage of an unexpected discovery: 1) you notice that something unexpected or unusual happens in a flask, 2) you realize that it is not "an unsuccessful experiment" but is "a bud" which grows up to be a significant new and big scientific discovery. To attain these two points, you have to be engaged in your own research and pay maximum attention to your experiments; what's more, you must always maintain a broad perspective beyond your research field. In order not to miss the encounter with serendipity, we should never forget the words of French scientist Louis Pascal, "Chance favors the prepared mind."

Finally, this year's prizes are the fruition of more than 30 years of work, as well as a celebration of our predecessors, who struggled and persevered so hard. That is why I believe this prize is a reminder of the importance of basic science, such as chemistry and physics, and I truly hope that many talented youngsters will be attracted by science and that Japan produces another string of Nobel laureates in 30 years later.

Takanori Shibata
Professor, Faculty of Science and Engineering, Waseda University

Profile

1966 Born
1989 Graduated from Faculty of Science, the University of Tokyo
1994 Obtained PhD from Graduate School of Science, the University of Tokyo
1994 Assistant Professor, Faculty of Science, Kitasato University
1995 Assistant Professor, Faculty of Science, Tokyo University of Science
1999 Associate Professor, Faculty of Science, Okayama University
2001 Postdoctoral Fellow, Harvard University (Professor E. J. Corey)
2003 Associate Professor, School of Science and Engineering, Waseda University
2004 Associate Professor, Faculty of Science and Engineering, Waseda University
2007 Took up current post

Awards: 2004 Incentive Award, in Synthetic Organic Chemistry, Japan