(Left to Right) Heck, Univ. of Delaware; Negishi, Purdue Univ.; Suzuki, Hokkaido Univ.

Matchmakers. This year's chemistry Nobel Prize winners, Richard Heck, Ei-ichi Negishi, and Akira Suzuki.

Carbon Catalysts Get Chemistry Nod

Staff Writer

Credit the matchmaker for this one. This year's Nobel Prize in chemistry went to three chemists—Ei-ichi Negishi, Akira Suzuki, and Richard Heck—for discovering catalysts used to tie the knot between carbon atoms on separate molecules. The ability to tailor such molecular unions has spawned whole sectors of advanced technology, making possible the synthesis of everything from anticancer drugs and agricultural pesticides to advanced displays and electronic chips in computers.

At the heart of these applications are organic molecules made from chains and rings of carbon atoms. Carbon is the key to organic chemistry—and life—thanks to its ability to link with its neighbors to form molecular chains and rings of an enormous variety of shapes, much as lumber can be nailed together to build houses of almost any design. To build synthetic molecules, chemists continually look for new ways to join together carbon atoms on separate molecules. The trouble is that in most organic molecules, the carbon atoms are happy with where they are and thus unlikely to react with their neighbors. In the early 1900s, German chemists came up with ways to link metal atoms to carbons, making them more reactive and willing to bond with neighbors. But the reactions weren't specific. Instead of producing just the desired molecule, the more-reactive carbons would bond willy-nilly with any carbon around, producing all sorts of junk that had to be tossed out.

In the late 1960s, Richard Heck, then with chemical manufacturing company Hercules Corp. in Wilmington, Delaware, and later at the University of Delaware, Newark, found that he could tailor just which carbons he wanted to link together. In one early example, Heck first linked a bromine atom to one of the six carbon atoms in a molecule of benzene. This slightly modified the electronic structure of the carbon and tagged it as the one that would react. He then added small, two-carbon molecules called olefins to the solution, as well as palladium. The palladium temporarily binds with both the carbon on the bromine-tagged benzene as well as one from the olefin, bringing them close enough to pair up. When they do so, they form styrene, the building block of polystyrene plastics. The reacting molecules kick the bromine out into solution and send the palladium on its way to orchestrate another hookup. In the late 1970s, Japanese-born Ei-ichi Negishi, who spent the bulk of his career at Purdue University in West Lafayette, Indiana, and Akira Suzuki of Hokkaido University in Sapporo, Japan, modified the approach, adding different tagging atoms as well as metals to tailor the reaction to make other organic compounds.

Today, the three approaches are collectively known in chemistry parlance as "palladium-catalyzed cross-coupling reactions," and they continue to grow more popular. "Of all methodologies developed over the past 50 years, it is safe to say that palladium-catalyzed cross-coupling methodologies have had the biggest impact on how organic compounds are made," says Eric Jacobsen, an organic chemist at Harvard University. "Cross-coupling methods are now used in all facets of organic synthesis, but nowhere more so than in the pharmaceutical industry, where they are used on a daily basis by nearly every practicing medicinal chemist."

As a result, Jacobsen and other chemists say they were not surprised by the award. "It was just a matter of time for this chemistry to be recognized," says Joseph Francisco, a chemist at Purdue University and the president of the American Chemical Society. Jacobsen says the Nobel Committee could have also chosen any of a few other cross-coupling pioneers, such as Barry Trost of Stanford University. But Nobel rules limit the committee to picking no more than three recipients. "I think they got it right," says Jeremy Berg, who heads the National Institute of General Medical Sciences in Bethesda, Maryland.

For Negishi in particular, the prize is a dream come true. After immigrating to the United States from Japan, Negishi says he had the opportunity to interact with several Nobel Laureates while studying at the University of Pennsylvania. The opportunity taught him to strive for his science to make a similar impact. "I began dreaming about this prize half a century ago," Negishi says. At a press conference televised in Japan, Suzuki said he hopes his work will have a similar effect on the next generation. "Japan has no natural resources. Knowledge is all we've got," Suzuki says.

With reporting by Dennis Normile in Tokyo.

Posted in Chemistry, Asia