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In situ acidic carbon dioxide/water system for selective oxybromination of electron-rich aromatics catalyzed by copper bromide

An-Hua Liu,Ran Ma,Meng Zhang,Liang-Nian He

Carbon dioxide, being one of the major greenhouse gases responsible for global warming, its atmospheric level grows ever faster since the beginning of industrial era. Great efforts have been devoted to developing versatile technologies/processes to adjust and manipulate the rapid growth of CO 2 emission. Besides CO 2 capture and storage/sequestration (CCS) to control its emission, chemical utilization of the captured CO 2 (CCU) emerges to be a rational technique for economical benefits as well as environmental concerns. As for the aim of CO 2 utilization, an environmentally benign CO 2 /water reversible acidic system was developed for the copper (II)-catalyzed selective oxybromination of electron-rich aromatics without the need of any conventional acid additive and organic solvent. Notably, up to 95% yields of the bromination products were attained with good regio-selectivity when cupric bromide was used as the catalyst and lithium bromide as a cheap and easy handling bromine source under supercritical CO 2 . The catalytic system worked well for electron-rich aromatics including ethers, sulfides and mesitylene. Carbonic acid in situ formed from CO 2 and water is supposed to act as the proton donator in the Brønsted acid-promoted reaction. Notably, CO 2 in this study serves as a reaction medium and a promoter in conjunction with water and also provides safe environment for aerobic reactions. Given with excellent reaction efficiency as well as no need of neutralization disposal, this process thus represents an environmentally friendly approach for aerobic bromination of aromatics with essential reduction of CO 2 emission as well as an economically beneficial way for application of captured CO 2 .