Recently, the team of Chen Qing'an, a researcher at the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, has made new progress in the reuse of halogenated organic pollutants. They developed a bromide-catalyzed chlorine transfer reaction that is capable of utilizing halogenated organic pollutants as halogen sources, thus enabling the reuse of different halogenated organic pollutants. This strategy provides a new method for constructing high value-added halogenated products and a new way to reuse halogenated organic pollutants. The related results were published in Nature Chemistry.
Due to the excessive use of halogenated compounds, a large number of halogenated organic pollutants (HOPs) are released into the environment, causing serious harm to the environment and human health. The reuse of HOPs not only provides a way to eliminate such substances, but also enables the synthesis of high value-added products and reduces greenhouse gas emissions associated with feedstock production.
Although HOPs are rich in halogens, they are difficult to use directly to synthesize other halides. Conventional methods for chlorination of C-H bonds utilize reagents that can directly or indirectly provide chlorine-positive species; however, in HOPs, the chlorides are mainly present in the chlorine-expressed electronegative form. Direct transfer utilization of chlorine using HOPs as chlorination reagents is very challenging, but is important for the reuse of HOPs.
Qingan Chen's team recently developed an alkyl bromide-catalyzed chlorine transfer reaction, using which not only can synthesize α-chloro ketones with high added value, but also can achieve chlorohydroxylation of olefins. In addition, the team conducted a series of controlled experiments and kinetic studies, and found that the reaction is based on the transfer of chlorine between different molecules via halogen exchange. Guided by the mechanism, the team realized the bromination of ketones and aromatics using the brominated organic pollutant hexabromocyclododecane (HBCD). Subsequently, to further validate the practicality of the reaction, the team applied the chlorine transfer reaction to the reuse of chlorinated organic pollutants. It was found that common chlorinated organic pollutants chlorinated paraffins (CPS), DDT (Dichlorodiphenyltrichloroethane), chloromethylated polystyrene (CMPS), and polyvinyl chloride (PVC) were able to serve as chlorine sources for the chlorine transfer reaction. The team directly utilized HBCD as the catalyst and PVC as the chlorine source to rapidly synthesize α-chloroketones, which were then simply converted to achieve the synthesis of the NSAIDs naproxen, ibuprofen, and felocoxib.
It was also found that waste PVC plastics were also able to be used as a chlorine source for the synthesis of chlorinated products, and despite the high amount of plasticizers in these waste plastics, there was no significant effect on the chlorination reaction. Therefore, this reaction has a good application prospect for the reuse of halogenated organic pollutants.
Related paper information: https://doi.org/10.1038/s41557-024-01551-8
