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Persulfate (S₂O₈²⁻) salts were reported to promote metal‐free aryldifluoromethylations using aryldifluoroacetic acids (Scheme 2.32); in 2016, Wu and coworkers reported an aryldifluoromethylation of ethynyl benziodoloxolone with aryldifluoroacetic acids by using potassium persulfate in acetonitrile/H₂O cosolvent (Scheme 2.32a) [63]; in contrast to Hashmi's conditions using silver catalyst (Scheme 2.25d) [56], Wu's conditions did not require any transition metal catalyst. Zhang and coworkers developed an aryldifluoromethylation of quinoxaline‐2(1H)‐ones with aryldifluoroacetic acid in dimethylsulfoxide (DMSO) (Scheme 2.32b) [64]. In both studies, persulfate salts were considered to oxidize the carboxylic acids and to generate the corresponding reactive difluorobenzyl radical via oxidative decarboxylation.

Scheme 2.32 Metal‐free aryldifluoromethylation using S₂O₈²⁻ as an oxidant.