Aug. 22, 2001 Chemistry researchers at the University of Illinois at Chicago have found a new way of performing a widely used chemical conversion process that may have practical application in the pharmaceutical industry, among others. UIC Distinguished Professor of organic chemistry David Crich, along with graduate student Santhosh Neelamkavil, initially published their findings July 3 on the Web version of the Journal of the American Chemical Society.
Crich and Neelamkavil used techniques from a promising new field called fluorous chemistry to modify an easy-to-use but malodorous oxidation process to convert alcohols into aldehydes and ketones.
Called the “Swern reaction,” after former Temple University chemist Daniel Swern, the process uses the cheap and readily available reagents dimethyl sulfoxide and oxalyl chloride rather than harmful heavy metal, chromium-based oxidizing agents.
Organic lab chemists prefer the Swern reaction because it is very convenient to use and applicable to a wide range of different and sensitive chemical structures, such as pharmaceutical intermediates.
But there is a big drawback to using this method for industrial-scale production. The byproduct is dimethyl sulfide, which has a boiling point of only about 100 degrees Fahrenheit (38 degrees Celcius).
“When you make it, you know about it,” said Crich. “It smells bad.”
Knowing that the Swern reaction could gain wide favor in chemical and pharmaceutical industries if the offensive byproduct could be contained, Crich and Neelamkavil created new reagents by adding strings of fluorine atoms—“fluorous ponytails” as Crich calls them—to dimethyl sulfoxide.
The result is fluorous dimethyl sulfoxide. The byproduct from the use of this new reagent is fluorous dimethyl sulfide—a chemical that has an easy-on-the-nose, very high boiling point.
“It’s odorless and easy to recycle,” said Crich. “It dissolves in a fluorous solvent. We treat it with hydrogen peroxide, clearly an environmentally friendly and cheap oxidant, which reoxidizes the fluorous dimethyl sulfide to dimethyl sulfoxide. So it gets recycled.”
“Now you can scale-up the Swern reaction, retaining all of its convenience with none of the odor problems,” said Crich. He adds that the kind of continuous extraction he uses in the lab to recycle could easily be set up on a production scale.
UIC holds a provisional patent on the process and licensing negotiations are under way.
Crich’s work in this area is supported by a research grant from the National Science Foundation.
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