Molecular Bonds Forging a New World

Fumitoshi Kakiuchi (Professor, Department of Chemistry)

In my laboratory, we conduct research aimed at developing efficient organic reactions using entirely new concepts and methodologies. In the section for books on organic reactions at a library or bookstore, you will find so many books that it is hard to decide which one to pick up. Opening these books reveals numerous achievements discovered through the wisdom and efforts of our predecessors. For the most part, the synthesis of compounds for one's own research objectives proceeds by drawing on the wisdom from reactions developed by these pioneers. Even for compounds that seem simple to synthesize at first glance, obtaining them with good selectivity can sometimes require an unexpectedly large number of steps. At times like these, a somewhat optimistic thought comes to mind: "If only I could cleave this bond here and reconnect it with that bond there, I could easily synthesize the target compound..." However, a "molecular transformation method with no precedent" cannot be found, no matter how many books you consult.

My field of research is organometallic chemistry. This field has been actively researched since around 1960. Since that time, it had been suggested that if the ubiquitous carbon-hydrogen bonds in organic compounds could be utilized in synthetic reactions, the number of reaction steps could be significantly reduced. Although much research was conducted over the subsequent 30 years, no clues to a solution were found.

As a university student, I too was fascinated by this research problem and spent my days thinking that I would one day take on the challenge. About 15 years ago, I suddenly succeeded in "creating something from nothing." I discovered a reaction that proceeds with high efficiency and selectivity to convert a carbon-hydrogen bond into a carbon-carbon bond by using ruthenium, which is in the same group as iron on the periodic table. This reaction involved reacting an aromatic ketone with an alkene to introduce an alkyl group to the benzene ring (Figure 1).

Whereas synthesizing the target compound previously required many steps, this reaction allows it to be obtained quantitatively in a single step. In particular, the formation of carbon-carbon bonds, which is crucial in organic synthesis, can be performed simply, providing a new methodology for organic synthesis techniques. (Figure 2)

This discovery served as a catalyst, sparking related research around the world and turning it into a rapidly developing field. Today, reactions that conventionally used organic halogen compounds can now be achieved by directly utilizing carbon-hydrogen bonds. I believe that by analyzing the characteristics of these reactions in detail, they will develop into an indispensable method for organic synthesis (Figure 3).

In our diversified modern society, the synthesis of a wide variety of substances is essential for sustaining an affluent and comfortable life. Using the methods of chemistry, we can transform molecules into completely different ones by rearranging the bonds between them. This also makes it possible to newly elicit the various properties and functions that these substances possess. I believe that chemistry will play an increasingly important role in the field of science in the future.