title: Visible light-promoted metal-free C-H activation: diarylketone-catalyzed selective benzylic mono- and difluorination.
abstract: We report herein an operationally simple method for the direct conversion of benzylic C-H groups to C-F. We show that visible light can activate diarylketones to abstract a benzylic hydrogen atom selectively. Adding a fluorine radical donor yields the benzylic fluoride and regenerates the catalyst. The selective formation of mono- and difluorination products can be achieved by catalyst control. 9-Fluorenone catalyzes benzylic C-H monofluorination, while xanthone catalyzes benzylic C-H difluorination. The scope and efficiency of this new C-H fluorination method are significantly better than those of the existing methods. This is also the first report of selective C-H gem-difluorination.
authors.affiliation: Division of Chemistry, Department of Biochemistry, The University of Texas Southwestern Medical Center , 5323 Harry Hines Boulevard, Dallas, Texas 75390-9038, United States.
authors.forename: Ji-Bao
authors.initials: JB
authors.lastname: Xia
authors.forename: Chen
authors.initials: C
authors.lastname: Zhu
authors.forename: Chuo
authors.initials: C
authors.lastname: Chen
mesh_terms: D001555:Benzene Derivatives / Q000737:chemistry*; D002384:Catalysis; D006845:Hydrocarbons, Fluorinated / Q000138:chemical synthesis* / Q000737:chemistry; D007659:Ketones / Q000737:chemistry*; D008027:Light; D015394:Molecular Structure
chemical_list: D001555:Benzene Derivatives; D006845:Hydrocarbons, Fluorinated; D007659:Ketones