Halex Reaction

DMSO is a proven solvent in the nucleophilic aromatic exchange of halogens (the Halex reaction). These reactions often require high temperatures, and dipolar aprotic solvents are typically preferred. The exchange of fluorine by the reaction of an alkali fluoride upon aromatic halides has long been known. Generally, such halogen exchange reactions are carried out mainly in such aprotic polar solvents as dimethyl sulfoxide (DMSO) at temperatures below the boiling points of these solvents [Ishikawa, Journal of Organic Synthetic Chemical Society, Japan, 25, Page 808 (1967); and Hudlicky, M., Chemistry of Organic Fluorine Compounds, page 112 (1976), John Wiley & Sons Press]. Some cases have been reported in which phase transfer catalysts such as crown compounds were added for the purpose of expediting reactions involved.

For example, p-chloronitrobenzene gave a nearly quantitative yield of the corresponding fluoro-compound in dry DMSO near the reflux temperature. [Zhu, Y. H.; Lou, H.; Lu, P.; Liu, J. G.; Zheng, X. M., Chinese Chemical Letters 13, No. 10, pp 919 . 920, (2002)]

See the work on Comparative Reaction Solvents.