Researchers Attempt Sigmatropic Rearrangement

Jack Trieu '11, Visiting Assistant Professor of Chemistry Joshua Ruppel, Eric Kuenstner '12
Jack Trieu '11, Visiting Assistant Professor of Chemistry Joshua Ruppel, Eric Kuenstner '12
Dressed in lab coats and goggles, Eric Kuenstner ’12 and Jack Trieu ’11 place a round-bottom flask on an instrument called a rotovap. With a push of a button the flask begins spinning, making the solution flow from the flask through coiled tubes. “It always makes me feel like a mad scientist,” Kuenstner laughs, and Trieu nods in agreement. But the result of this seemingly diabolical processing is hardly sinister; under the direction of Visiting Assistant Professor of Chemistry Joshua Ruppel, the students are looking to find the most favorable conditions for a [2,3] sigmatropic rearrangement to occur.

In a sigmatropic rearrangement, the bonds in a molecule change location. When used in a controlled manner, sigmatropic reactions can yield carbon-carbon bonds, which are often found in nature but are difficult to recreate in the lab, or nitrogen-carbon and sulfur-carbon bonds, which have important applications in the human body. Significant for humans, sigmatropic reactions have been thoroughly studied, and the conditions under which they occur have been clearly outlined.

Kuenstner and Trieu have recreated a lot of what they have read about in this reaction, but are now looking beyond the literature. They are experimenting with different substrates (the material that is reacted) and catalysts (the materials that cause the reaction to happen) to make the reaction more likely to happen. They are using porphyrins, very large organic molecules that allow the reactions to have high yields, as the catalyst and are varying the substituents, atom chains that hang off of the central molecule, as well as the type of metal at the center of the catalyst. By changing all of these factors that influence the reaction, the team hopes to find the reaction that produces the greatest yield of these coveted molecules with such significant and elusive bonds.

As their substrate, the team is trying a little-used type of compound called ylides (ILL-ids). Ylides are organic compounds that facilitate certain kinds of reactions, and sulfur ylides are a particularly reactive type of ylide. A sulfur ylide consists of a sulfide compound with an akyl, allyl or aryl molecule bonded to it; after reacting this compound with the right type of catalyst, the bonds of the molecule rearrange so that two carbon atoms are bonded together.

“Right now, we’re using [this reaction] to prove a concept,” Trieu said. “Eventually we hope to use it with nitrogen, which is more prevalent in the human body.” Nitrogen is more useful for the human body because the body more easily absorbs the resultant amines (compounds that contain a basic nitrogen atoms). With nitrogen, this methodology can be used to make complex molecules or natural products that can be used for medicinal or pharmaceutical purposes, such as in Singulair, which uses sulfur-carbon, nitrogen-carbon and carbon-carbon bonds to treat asthma and allergies.

But the team’s research has other applications in the world of chemistry research. “Using catalysts can make reactions greener, as reactions usually require a lot of solvents that are hazardous to the environment or human health,” Trieu explained. With more experimentation with catalysts and natural ways to create a coveted synthetic product, researchers could find a compromise between making the compounds they need and environmental conservation.

Kuenstener and Trieu's summer research was funded through the Edward and Virginia Taylor Fund for Student/Faculty Research in Chemistry, established in 2008 through a gift from Ted ’46 and Virginia to inspire students interested in chemical research and to facilitate their work with outstanding faculty.

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