Iron-Catalyzed Chemoselective C-N Coupling Reaction: A Protecting-Group-Free Amination of Aryl Halides Bearing Amino or Hydroxy Groups

A chemoselective C-N coupling (Buchwald-Hartwig-type) reaction of diarylamines with aryl halides bearing non-protected amino or hydroxy groups proceeds in the presence of a simple iron catalyst. Upon treatment with Grignard reagents, various diarylamines can be cross-coupled with halocarbazoles, haloindoles, haloanilines, and halophenols to afford the corresponding triarylamines, without the undesired dimerization or oligomerization of the starting aryl halides. DFT studies on the dimeric iron amide intermediates reveal that the reductive elimination can be the selectivity determining step. Finally, a short-step synthesis of a thermally activated delayed-fluorescence emitter, DACT-II, demonstrates the synthetic utility of the present method.