Kinetic and product studies on Ullmann amination of 1-halogenoanthraquinones catalysed by copper(I) salts in acetonitrile solution

Bethell, Donald; Jenkins, Iwan L.; QUAN, P. M.

doi:10.1039/p29850001789

Cited by 24 publications

(16 citation statements)

References 3 publications

(3 reference statements)

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“…13 Although the current evidence disfavors radical reactions of aryl halides with copper complexes containing neutral dative nitrogen ligands, 14 the difluoromethylation in the current work occurs through complexes lacking such ligands and, therefore, could follow a different pathway. To probe the potential inter-mediacy of aryl radicals during this difluoromethylation reaction, we conducted the difluoromethylation of 1-(allyloxy)-2-iodobenzene (Scheme 2).…”

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confidence: 74%

Copper-Mediated Difluoromethylation of Aryl and Vinyl Iodides

2012

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Selectively fluorinated molecules are important as materials, pharmaceuticals, and agrochemicals, but their synthesis by simple, mild, laboratory methods is challenging. We report a straightforward method for the cross-coupling of a difluoromethyl group with readily available reagents to form difluoromethylarenes. The reaction of electron-neutral, electron-rich, and sterically hindered aryl and vinyl iodides with the combination of CuI, CsF and TMSCF2H leads to the formation of difluoromethylarenes in high yield with good functional group compatibility. This transformation is surprising, in part, because of the prior observation of the instability of CuCF2H.

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confidence: 74%

Copper-Mediated Difluoromethylation of Aryl and Vinyl Iodides

2012

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“…The mechanism of carbon–heteroatom bond formation from copper alkoxides and amides has been proposed in some cases to occur by radical20,44–46 and in other cases by nonradical27,47–53 pathways 5,54. The proposed radical mechanism is triggered by electron transfer from copper to the aryl halide to form a haloarene radical anion, which eliminates the halide to form a neutral aryl radical.…”

Section: Resultsmentioning

confidence: 99%

Copper Complexes of Anionic Nitrogen Ligands in the Amidation and Imidation of Aryl Halides

et al. 2008

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Copper(I) imidate and amidate complexes of chelating N,N-donor ligands, which are proposed intermediates in copper-catalyzed amidations of aryl halides, have been synthesized and characterized by X-ray diffraction and detailed solution-phase methods. In some cases, the complexes adopt neutral, three-coordinate trigonal planar structures in the solid state, but in other cases they adopt an ionic form consisting of an L 2 Cu + cation and a CuX 2 − anion. A tetraalkylammonium salt of the CuX 2 − anion in which X = phthalimidate was also isolated. Conductivity measurements and 1 H NMR spectra of mixtures of two complexes all indicate that the complexes exist predominantly in the ionic form in DMSO and DMF solutions. One complex was sufficiently soluble for conductance measurements in less polar solvents and was shown to adopt some degree of the ionic form in THF and predominantly the neutral form in benzene. The complexes containing dative nitrogen ligands reacted with iodoarenes and bromoarenes to form products from C-N coupling, but the ammonium salt of [Cu(phth) 2 ] − did not. Similar selectivities for stoichiometric and catalytic reactions with two different iodoarenes and faster rates for the stoichiometric reactions implied that the isolated amidate and imidate complexes are intermediates in the reactions of amides and imides with haloarenes catalyzed by copper complexes containing dative N,N ligands. These amidates and imidates reacted much more slowly with chloroarenes, including chloroarenes that possess more favorable reduction potentials than some bromoarenes and that are known to undergo fast dissociation of chloride from the chloroarene radical anion. The reaction of o-(allyloxy)iodobenzene with [(phen) 2 Cu][Cu(pyrr) 2 ] results in formation of the C-N coupled product in high yield and no detectable amount of the 3-methyl-2,3-dihydrobenzofuran or 3-methylene-2,3-dihydrobenzofuran products that would be expected from a reaction that generated free radicals. These data and computed reaction barriers argue against mechanisms in which the haloarene reacts with a two-coordinate anionic copper species and mechanisms that start with electron transfer to generate a free iodoarene radical anion. Instead, these data are more consistent with mechanisms involving cleavage of the carbon-halogen bond within the coordination sphere of the metal.

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“…Whether a Cu III complex was ever formed, or the product was formed directly, could not be ascertained from these investigations. Bethell and coworkers observed that products consistent with the formation of a Cu III intermediate are formed in related reactions of bromoanthraquinone with primary amines 28. Huffman and Stahl have demonstrated that N-arylation occurs via the coupling of Cu III (aryl) species with nitrogen-based nucleophiles 29.…”

Section: Introductionmentioning

confidence: 99%

Computational Explorations of Mechanisms and Ligand-Directed Selectivities of Copper-Catalyzed Ullmann-Type Reactions

et al. 2010

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Computational investigations of ligand-directed selectivities in Ullmann-type coupling reactions of methanol and methylamine with iodobenzene by β-diketone-and 1,10-phenanthroline-ligated Cu(I) complexes are reported. Density functional theory (DFT) calculations with several functionals were performed on both the nucleophile formation and aryl halide activation steps of these reactions. The origin of ligand-directed selectivities in N-vs. O-arylation reactions as described in a previous publication (J. Am. Chem. Soc. 2007, 129, 3490-3491) were studied and explained. The selectivities observed experimentally are not derived from initial Cu(I)-nucleophile formation, but from the subsequent steps involving aryl halide activation. The arylation may occur via single-electron transfer (SET) or iodine atom transfer (IAT), depending on the electrondonating ability of the ligand and nucleophile. Mechanisms involving either oxidative addition/ reductive elimination or sigma-bond metathesis are disfavored. SET mechanisms are favored in reactions promoted by the β-diketone ligand; N-arylation is predicted to be favored in these cases, in agreement with experimental results. The phenanthroline ligand promotes O-arylation reactions via IAT mechanisms in preference to N-arylation reactions, which occur via SET mechanisms; this result is also in agreement with experimental results.

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Kinetic and product studies on Ullmann amination of 1-halogenoanthraquinones catalysed by copper(I) salts in acetonitrile solution

Cited by 24 publications

References 3 publications

Copper-Mediated Difluoromethylation of Aryl and Vinyl Iodides

Copper-Mediated Difluoromethylation of Aryl and Vinyl Iodides

Copper Complexes of Anionic Nitrogen Ligands in the Amidation and Imidation of Aryl Halides

Computational Explorations of Mechanisms and Ligand-Directed Selectivities of Copper-Catalyzed Ullmann-Type Reactions

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