Replacement of BF4− by PF6− makes Selectfluor greener

A combination of F-TEDA-PF6 and CuBr (0.1 equiv.) provides a potent oxidant that readily oxidizes amides to provide imides at room temperature. Replacement of BF4−, the anion of Selectfluor (F-TEDA-BF4), by PF6−, dramatically reduces CuBr loading in this oxidative reaction. A possible rationale for this dramatic counterion effect is provided.

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► Selectfluor®/CuBr oxidizes amides to provide imides at room temperature.
► The choice of counterion for Selectfluor® affects CuBr loading dramatically.
► A rationale for thecounterion effect is provided.