title: Transition-metal-free direct arylation: synthesis of halogenated 2-amino-2'-hydroxy-1,1'-biaryls and mechanism by DFT calculations.
abstract: A transition-metal-free, regioselective direct aryl-aryl bond-forming process for the synthesis of halogenated 2-amino-2'-hydroxy-1,1'-biaryls that are currently either inaccessible or challenging to prepare using conventional methods is disclosed. The addition of ArMgX to an o-halonitrobenzene at low temperature generates a transient N,O-biarylhydroxylamine that rapidly undergoes either [3,3]- or [5,5]-sigmatropic rearrangement in one-pot to form a 2-amino-2'-hydroxy-1,1'-biaryl or 1-amino-1'-hydroxy-4,4'-biaryl, respectively. The periselectivity is controlled by the choice of solvent and temperature. This direct arylation process is also readily scalable (1-10 mmol). DFT calculations suggest that from the N,O-biarylhydroxylamine intermediate there is a low-energy stepwise pathway that involves initial Mg-mediated N-O bond cleavage followed by pathway branching toward either [3,3]- or [5,5]-rearrangement products via C-C bond formation and rearomatization.
authors.affiliation: Division of Chemistry, Department of Biochemistry, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390, USA.
authors.forename: Hongyin
authors.initials: H
authors.lastname: Gao
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Ess
authors.forename: Muhammed
authors.initials: M
authors.lastname: Yousufuddin
authors.forename: László
authors.initials: L
authors.lastname: Kürti
mesh_terms: D054879:Halogenation; D006841:Hydrocarbons, Aromatic / Q000138:chemical synthesis* / Q000737:chemistry; D008958:Models, Molecular; D013237:Stereoisomerism
chemical_list: D006841:Hydrocarbons, Aromatic