title: Palladium-catalyzed chelation-assisted aromatic C-H nitration: regiospecific synthesis of nitroarenes free from the effect of the orientation rules.
abstract: A palladium-catalyzed chelation-assisted ortho-nitration of aryl C-H bond is described. A range of azaarenes such as 2-arylquinoxalines, pyridines, quinoline, and pyrazoles were nitrated with excellent chemo- and regioselectivity. Using the O-methyl oximyl group as a removable directing group, the regiospecific synthesis of a variety of o-nitro aryl ketones was achieved starting from aryl ketones via a three-step process involving the Pd-catalyzed ipso-nitration of C-H bond as a key step. Mechanistic investigations support a silver-mediated radical mechanism involving Pd((II/III) and/or Pd(II/IV) catalytic cycles under oxidizing conditions.
authors.affiliation: State Key Laboratory Breeding Base of Green Chemistry-Synthesis Technology, Zhejiang University of Technology, Hangzhou 310014, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.forename: Shaojie
authors.initials: S
authors.lastname: Lou
authors.forename: Yunkui
authors.initials: Y
authors.lastname: Liu
authors.forename: Zhenyuan
authors.initials: Z
authors.lastname: Xu