| TECHNOLOGY |
MEANWHILE, Dowpharma has invented a semicontinuous Swern oxidation to make an advanced drug intermediate. According to Dowpharma process chemist J. Russell McConnell, the Swern oxidation usually is run under cryogenic conditions because the intermediates are unstable. However, such conditions are difficult to sustain at a large scale. If the residence time of the intermediates could be reduced, the reaction could work at higher temperatures. "The approach we took was to generate the intermediates inside an in-line reactor and give them very little time to do anything else," he says.
The process is only partly continuous. Two separate reagent streams come together in an in-line reactor--a tube outside of and connected to a conventional stirred-tank reactor. The intermediate forms as the reactants traverse the tube and immediately is dumped into the stirred tank, where it is converted to the aldehyde. Yields are only slightly higher than those realized under cryogenic conditions, but operability is vastly better, McConnell says
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