title: Photochemical Nickel-Catalyzed C-H Arylation: Synthetic Scope and Mechanistic Investigations.
abstract: An iridium photocatalyst and visible light facilitate a room temperature, nickel-catalyzed coupling of (hetero)aryl bromides with activated α-heterosubstituted or benzylic C(sp3)-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(sp3)-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.
authors.affiliation: Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania , Philadelphia, Pennsylvania 19104-6323, United States.
authors.forename: Drew R
authors.initials: DR
authors.lastname: Heitz
authors.affiliation: Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania , Philadelphia, Pennsylvania 19104-6323, United States.
authors.forename: John C
authors.initials: JC
authors.lastname: Tellis
authors.affiliation: Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania , Philadelphia, Pennsylvania 19104-6323, United States.
authors.forename: Gary A
authors.initials: GA
authors.lastname: Molander