Photochemical Nickel-Catalyzed C–H Arylation: Synthetic Scope and Mechanistic Investigations

An iridium photocatalyst and visible light facilitate a room temperature, nickel-catalyzed coupling of (hetero)aryl bromides with activated -heterosubstituted or benzylic C(sp 3 )-H bonds. Mechanistic investigations on this unprecedented transformation have uncovered the possibility of an unexpected mechanism hypothesized to involve a Ni-Br homolysis event from an excited-state nickel complex. The resultant bromine radical is thought to abstract weak C(sp 3 )-H bonds to generate reactive alkyl radicals that can be engaged in Ni-catalyzed arylation. Evidence suggests that the iridium photocatalyst facilitates nickel excitation and bromine radical generation via triplet-triplet energy transfer.

• BS
  Bristol-Myers Squibb
• NI
  National Institute of General Medical Sciences

  Award: R01-GM-113878
• DO
  Division of Chemistry

  Award: CHE-1362841