Oxygen is one of the most essential elements to human life. Thanks to new chemistry techniques developed within the David Powers Laboratory at Texas A&M University, it's now more essential to a broad array of organic reactions -- a major goal in the development of sustainable organic chemistry.

The process of converting simple organic molecules into more complex, functional molecules frequently involves oxidation chemistry. In biology, enzymes utilize O2 -- oxygen's most stable form, dioxygen -- as a chemical oxidant to oxidize substrate molecules. While O2 would be an ideal chemical reagent for synthetic chemistry because it is inexpensive and environmentally benign, Powers says it is rarely used because its specific electronic structure causes it to react with organic molecules either too slowly or via uncontrolled processes. For example, he notes the fogging of car headlghts is due to slow oxidative damage of the plastic by reaction with O2 .

A major goal of oxidation chemistry is to use O2 from air as the chemical oxidant to achieve oxidation chemistry for organic synthesis -- a goal that Powers' group has achieved by using O2 as a selective reagent in organic chemistry. Their new strategy uses O2 to synthesize hypervalent iodine reagents from O2, a broadly useful class of oxidants that can be applied to the oxidation of a diverse set of organic substrate oxidation reactions.

"Our methods provide new strategies to make the materials that we rely on as a society, from organic materials to pharmaceuticals to pesticides, in a more sustainable fashion," Powers said.

The group's research, funded in part by the Welch Foundation, is described in a paper published today in Nature Chemistry.

"Our research was guided by the hypothesis that synthesis of hypervalent iodine reagents from O2 would immediately provide a strategy to accomplish a large set of organic oxidation reactions using O2," Powers said. "The ultimate goal of this line of research is to replace many of the wasteful processes that are currently used to synthesize fine chemicals, such as pharmaceuticals, with sustainable processes using O2."

The critical discovery that allowed Powers, along with graduate students Asim Maity and Sung-Min Hyun, to generate hypervalent iodine reagents from O2 was that intermediates in aldehyde autoxidation -- one of the oldest-known reactions of O2 with organic molecules -- could be intercepted and diverted towards the oxidation of aryl iodides. The only chemical byproduct of the new process is an equivalent of acetic acid and a method that opens the door to a wealth of potential in synthetic chemistry.

"Our paper demonstrates that it is possible to generate hypervalent iodine reagents from O2 and then to use that chemistry to accomplish aerobic oxidation chemistry as a variety of classes of organic molecules," Powers said. "This proof-of-strategy raises many new questions that we are working hard to address, including how the oxidation reaction happens a molecular level, how generally it can be applied, and how to develop second-generation methods to generate hypervalent iodine reagents that are waste-free."

Powers joined the Texas A&M Department of Chemistry in 2015 after obtaining his Ph.D. in organic chemistry at Harvard University in 2011 and completing a four-year National Institutes of Health (NIH)/National Research Service Award (NRSA) Postdoctoral Fellowship at the Massachusetts Institute of Technology and Harvard. Earlier this year, he was honored as one of 37 national recipients of the 2017 Oak Ridge Associated Universities (ORAU) Ralph E. Powe Junior Faculty Enhancement Award recognizing his research accomplishments and career potential.

The group's paper, "Oxidase catalysis via aerobically generated hypervalent iodine intermediates," can be viewed online along with related figures and captions.

To learn more about Powers and his research, go to http://www.chem.tamu.edu/faculty/david-powers/.

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Contact: Shana K. Hutchins, (979) 862-1237 or shutchins@science.tamu.edu or Dr. David C. Powers, (979) 862-3089 or david.powers@chem.tamu.edu

Hutchins Shana

  • Dr. David C. Powers

  • The Powers Research Group (Credit: David Powers.)

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