title: Nickel-catalyzed asymmetric α-arylation and heteroarylation of ketones with chloroarenes: effect of halide on selectivity, oxidation state, and room-temperature reactions.
abstract: We report the α-arylation of ketones with a range of aryl chlorides with enantioselectivities from 90 to 99% ee catalyzed by the combination of Ni(COD)(2) and (R)-BINAP and the coupling of ketones with a range of heteroaryl chlorides with enantioselectivities up to 99% ee catalyzed by Ni(COD)(2) and (R)-DIFLUORPHOS. The analogous reactions of bromoarenes occur with much lower enantioselectivities. Mechanistic studies showed that the difference in the rates of decomposition of the arylnickel(II) halide intermediates to {[(R)-BINAP]NiX}(2) likely accounts for the difference in the enantioselectivities of the reactions of bromoarenes and chloroarenes. This catalyst decomposition can be overcome by conducting the reactions with [(R)-BINAP]Ni(η(2)-NC-Ph) (4), which undergoes oxidative addition to haloarenes at room temperature.
authors.affiliation: Department of Chemistry, University of Illinois, 600 South Mathews Avenue, Urbana, Illinois 61801, USA.
authors.forename: Shaozhong
authors.initials: S
authors.lastname: Ge
authors.forename: John F
authors.initials: JF
authors.lastname: Hartwig
mesh_terms: D002384:Catalysis; D006842:Hydrocarbons, Brominated / Q000737:chemistry*; D006843:Hydrocarbons, Chlorinated / Q000737:chemistry*; D007659:Ketones / Q000138:chemical synthesis* / Q000737:chemistry*; D015394:Molecular Structure; D009532:Nickel / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D013237:Stereoisomerism; D013696:Temperature
chemical_list: D006842:Hydrocarbons, Brominated; D006843:Hydrocarbons, Chlorinated; D007659:Ketones; D009942:Organometallic Compounds; D009532:Nickel