Synthesis of (Poly)halo-Substituted Diarylsulfones through Palladium-Catalyzed C-H Bond Sulfonylation Using (Poly)Halobenzenesulfonyl Chlorides

The reactivity of (poly)halo-substituted benzenesulfonyl chlorides in palladium-catalyzed ortho-directed C-H bond sulfonylation of 2-arylpyridines was investigated. The use of Ag2CO3 in concert with Cu(OAc)(2) was found to be critical to promote the chemoselective sulfonylation reaction. Fluoro-, chloro-, bromo-, and even iodo-benzenesulfonyl chlorides react nicely to afford halo-substituted diarylsulfones in good to high yields without cleavage of the C-halo bonds, allowing further transformations.