Scientists open new frontier of chemical "space"

Chuck Bednar for redOrbit.com – Your Universe Online
A new method for joining complex organic molecules could be used to create fabrics, dyes, plastics, pharmaceuticals and other materials, chemists from The Scripps Research Institute (TSRI) report in a paper published online Wednesday in the journal Nature.
While carbon-to-carbon coupling methods are essential for chemistry, they can fail is either of the starting compounds have miniscule reactive regions known as “functional groups” attached to their main structure. Also, they often do not work well around non-carbon atoms known as “heteroatoms,” which are vital for chemical synthesis and include oxygen, nitrogen and iodine.
The powerful new technique developed by the TSRI team allows scientists to join two compounds known as olefins to create a new bond between their carbon-atom backbones, they explained. It is what chemists refer to as a “mild” reaction, meaning that it does not require harsh chemicals or extreme temperatures or pressures that could damage fragile building blocks.
“We are rewriting the rules for how one thinks about the reactivity of basic organic building blocks, and in doing so we’re allowing chemists to venture where none has gone before,” said Phil S. Baran, the Darlene Shiley Chair in Chemistry at TSRI.
“Functional groups that would be destroyed by other cross-coupling methods are totally unscathed when using our method,” added Julian C. Lo, a graduate student who was a co-lead author of the paper along with research associate Jinghan Gui.
The researchers came up with the idea for the new technique by working on a project in Baran’s laboratory which required them to synthesize natural compounds found in traditional Chinese medicines. As they worked to build the desired molecules, they discovered that they could adapt the technique they were using to join two relatively simple olefins together.
That research was published back in January, and Lo, Gui and their colleagues set to work adapting the methods used to combine more complex olefins attached to heteroatoms. Using a simple iron catalyst, a commercially-available silane and ethanol as a solvent, they were able to perform the reactions in an open flask, eliminating the need to exclude air or moisture.
“Importantly, the chemists showed that their reaction can be used to make compounds that were previously either unpractical to synthesize or couldn’t have been made at all,” the researchers said, noting that they were able to use the new technique to create over 60 compounds, 90 percent of which were new chemical entities, according to Baran.
“We expect that this method will have immediate application to pharmaceuticals, materials, and even agricultural and fragrance chemistry,” he added, noting that the method has already been put to use to help a company solve a difficult chemical synthesis problem. “This new chemistry allows for bond constructions that have previous been simply unimaginable.”
Other credited authors of the paper included Yuki Yabe and Chung-Mao Pan of TSRI’s Department of Chemistry. Funding for their research was provided by the US National Institute of General Medical Sciences, a division of the National Institutes of Health (NIH)
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