Application of a new kinetic method in the investigation of cleavage reactions of haloaromatic radical anions†

Enemærke, Rasmus J.; Christensen, Torben Bo; Jensen, Henrik; Daasbjerg, Kim

doi:10.1039/b102835a

Cited by 105 publications

(111 citation statements)

References 75 publications

(69 reference statements)

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“…This table also shows the potential for reduction of 1-naphthyl triflate, which forms aryl oxide upon reduction by S–O bond cleavage 42. The rate constants for halide dissociation have been measured several times,40,41,43 and a range of values are provided in the table. However, the rate constants measured for chloride dissociation from the radical anion of 4-chlorobenzonitrile and for bromide dissociation from 1- and 2-bromonaphthalene are within a factor of 3 of each other when measured by the same method 40,41,57…”

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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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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“…The reduction potential of this bromoarene is higher than that of some of the aryl iodides in Table 1. 20 Thus, the formation of an aryl radical by an outer-sphere electron transfer with this aryl bromide should occur at a rate that is comparable to the rate of the reactions of aryl iodides. 20 However the aryl bromide reacted to less than 30% conversion and formed the aryl fluoride in only 19% yield (eq 5).…”

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confidence: 99%

“…20 Thus, the formation of an aryl radical by an outer-sphere electron transfer with this aryl bromide should occur at a rate that is comparable to the rate of the reactions of aryl iodides. 20 However the aryl bromide reacted to less than 30% conversion and formed the aryl fluoride in only 19% yield (eq 5). A higher conversion of the aryl bromide would be expected if the copper system reacted with the aryl halide by a single-electron transfer pathway.…”

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confidence: 99%

Copper-Mediated Fluorination of Aryl Iodides

2012

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The synthesis of aryl fluorides has been a topic of considerable interest because of the importance of aryl fluorides in pharmaceuticals, agrochemicals and materials. The stability, reactivity and biological properties of aryl fluorides can be distinct from those of the corresponding arenes. Methods for the synthesis of aryl fluorides, however, are limited. We report the conversion of a diverse set of aryl iodides to the corresponding aryl fluorides. This reaction occurs with a cationic copper reagent and silver fluoride. Preliminary results suggest this reaction is enabled by a facile reductive elimination from a cationic aryl copper(III) fluoride.

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“…This result implies that the copper-mediated trifluoromethylation reaction proceeds without the intermediacy of an aryl radical from electron transfer and expulsion of iodide. [24–26] …”

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confidence: 99%

A Broadly Applicable Copper Reagent for Trifluoromethylations and Perfluoroalkylations of Aryl Iodides and Bromides

et al. 2011

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Application of a new kinetic method in the investigation of cleavage reactions of haloaromatic radical anions†

Cited by 105 publications

References 75 publications

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

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

Copper-Mediated Fluorination of Aryl Iodides

A Broadly Applicable Copper Reagent for Trifluoromethylations and Perfluoroalkylations of Aryl Iodides and Bromides

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