Cobalt-catalyzed C-H arylations, benzylations, and alkylations with organic electrophiles and beyond.

Catalytic C-H functionalizations are increasingly viable tools for sustainable syntheses. In recent years, inexpensive cobalt complexes were identified as powerful catalysts for C-H arylations with challenging organic electrophiles. In particular, cobalt complexes of N-heterocyclic carbenes enabled high catalytic efficacy under exceedingly mild reaction conditions. This strategy set the stage for challenging direct alkylations with primary and sterically hindered secondary alkyl halides. Herein, the recent rapid evolution of cobalt-catalyzed C-H transformations with organic electrophiles is reviewed until summer 2014.