Wednesday, November 13, 2013

Organic chemists now forming global bonds

"When I return to Japan, I'm going to be bringing back a lot of new ideas," says Atsushi Yamaguchi, at work in an Emory lab. Chemistry labs in the NSF Center for Selective C-H Functionalization are boosting their power by collaborating instead of competing. Photo by Carol Clark.

By Carol Clark

Atsushi Yamaguchi, a graduate student of chemistry from Nagoya University in Japan, is spending most of the fall semester as an exchange student, working in the Huw Davies lab at Emory.

“In Nagoya, you only see buildings,” he says. “In Atlanta, I can see lots of trees and squirrels.”

But the best part of the exchange experience, Yamaguchi adds, is the insider’s view he’s getting of top organic chemistry labs throughout the United States that are part of the National Science Foundation’s Center for Selective C-H Functionalization (CCHF).

“Before I came here, I only talked about chemistry with my other lab members, who have my same specialty,” Yamaguchi says.

Now, he’s learning new techniques of hands-on chemistry at Emory, while also joining in regular video conferences with chemists from the 14 top U.S. research universities involved in the CCHF. “When I return to Japan, I’m going to be bringing back a lot of new ideas,” Yamaguchi says.

The CCHF, headquartered at Emory, is pioneering a whole new way for organic chemists to teach and do research. A National Center for Chemical Innovation, the CCHF is funded through a $20 million NSF grant.

“We’ve gotten used to collaborating nationally through video-conferences,” says Huw Davies, the CCHF director and Emory professor of organic chemistry. “Now we’re going international.”

Video conference sessions link the Emory lab to other top organic chemistry labs around the country through the CCHF, which is now poised to connect labs globally.

Boosted this fall by an additional $635,000 from the NSF program Science Across Virtual Institutes (SAVI), the CCHF is expanding to include organic chemistry labs in Nagoya University, the Korea Advanced Institute of Science and Technology (KAIST) in South Korea, Cambridge University in England and the Max Planck Institute in Germany.

Each year, students and post-docs from Emory and other universities involved in the CCHF can spend several months doing chemistry abroad, while foreign students spend time at labs in the United States.

“The idea is to have cultural exchanges while also building collaborative research,” Davies explains. “It’s an incredibly valuable experience for students, who will ultimately be involved in research in a global environment as organic chemistry enters a new era.”

Traditionally, organic chemistry has focused on the division between reactive, or functional, molecular bonds and the inert, or non-functional bonds carbon-carbon (C-C) and carbon-hydrogen (C-H). The inert bonds provide a strong, stable scaffold for performing chemical synthesis on the reactive groups. C-H functionalization flips this model on its head.

Watch a video on how the CCHF is changing chemistry research and education:

“Governments around the world are investing hundreds of millions of dollars into C-H functionalization research,” Davies says. “In terms of organic synthesis and new methods of synthesis, it’s where the action is.”

C-H functionalization holds the potential to make organic synthesis faster, simpler and greener, and could open up whole new ways to develop drugs and other fine-chemical products, for use in everything from agriculture to electronics.

Many challenges remain, however, before C-H functionalization can be fully optimized for broad applications. The global network forged by the CCHF brings together leading players from around the world, representing a range of specialties that will be required to make the critical breakthroughs necessary to bring C-H functionalization into the mainstream of chemical synthesis.

The CCHF’s new model for research, breaking down individual lab walls to create a global collaboration of chemists taking different approaches to similar problems, has already resulted in dozens of research papers.

The journal Science recently published a CCHF finding that resulted from a collaboration between the Davies lab at Emory and the lab of John Berry at the University of Wisconsin-Madison.

The Davies lab has developed a powerful rhodium catalyst to drive chemical reactions for C-H functionalization, and a special class of highly reactive dirhodium carbene intermediates. The lab has been refining these carbenes for more than 25 years, to tame their reactivity so they can be used to perform selective, controllable reactions.

Watch a video of the reaction involved in the research paper, above.

Efforts by the Davies lab and others to isolate and study the intermediate steps of the dirhodium metal complex reactions have been hindered by their extreme efficiency and speed, since they react at about 300 times per second.

The Berry lab found a way to freeze and stabilize one step of the process long enough to get an actual glimpse into the workings of the mechanism. Ultraviolet-visible spectrometry showed the formation of a new molecule as the green starting material changed to a blue color that faded over time.

More collaborators helped give an even fuller picture of the intermediate compound. Jochen Autschbach from the University of Buffalo used density function theory to predict the nuclear magnetic resonance features of the compound, and Kyle Lancaster from Cornell University elucidated the compound’s structure using a series of X-ray absorption spectroscopy experiments.

“This is a seminal paper for the fundamental understanding of this chemistry, and it could not have been done without the ability to collaborate across a wide range of specialties,” Davies says. “Our lab has been broadly making C-H bonds functional for years, but there was always this mysterious black box that we couldn’t see into during the reactions. Now we can test the theoretical, computational models we’ve developed against the actual reactions. We can gather more information about bond strength and electron properties, so we’re not doing research in the dark.”

Davies expects the breakthrough to speed up the process of refining and improving the rhodium catalyst, one of the most promising and versatile of the multiple approaches under way to bring C-H functionalization to the forefront of organic chemistry.

NSF chemistry center opens new era in organic synthesis

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