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Issue 48, 2019
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Deciphering the mechanism of copper-catalyzed N-arylation between aryl halides and nitriles: a DFT study

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Abstract

The mechanism of the CuI/DMEDA-catalyzed tandem hydrolysis/N-arylation of benzonitrile with aryl iodide was studied using the DFT method. Two possible copper complexes, Int1 [CuI(DMEDA)] and Int2 (anionic analogue of Int1), were investigated for four plausible reaction pathways involved in the hydrolysis of benzonitrile. In paths A and C, the iodide ligand of Int1 and Int2 needs to be replaced with a hydroxide ion to give hydroxide-coordinated intermediates Int1-1 and Int2-1, which can eventually react with benzonitrile to hydrolyze their nitrile group to yield intermediates Int1-3 and Int2-3, respectively. In contrast, the iodide ligand can initially be replaced by benzonitrile to form benzonitrile-coordinated intermediates Int1-2 and Int2-2 (described in paths B and D), which react with the hydroxide ion to hydrolyze the nitrile group of the coordinated benzonitrile ligand to give Int1-3 and Int2-3, respectively. The intrinsic reaction coordinate (IRC) analysis of the transition states involved in the hydrolysis validated paths A and C. The activation energy and overall energy barrier for path A (25.9 and 10.6 kcal mol−1) is lower than that for path C (27.5 and 19.7 kcal mol−1), respectively. Intermediate Int1-3 tautomerizes to give intermediate Int1-4, which undergoes C–N coupling reaction with iodobenzene via an oxidative addition/reductive elimination mechanism. The hydrolysis of the nitrile group was proven to be the rate-limiting step since it has a higher activation energy (25.9 kcal mol−1) than that of the oxidative addition (22.9 kcal mol−1) and reductive elimination reactions (6.9 kcal mol−1).

Graphical abstract: Deciphering the mechanism of copper-catalyzed N-arylation between aryl halides and nitriles: a DFT study

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Publication details

The article was received on 25 Jul 2019, accepted on 11 Nov 2019 and first published on 12 Nov 2019


Article type: Paper
DOI: 10.1039/C9NJ03860D
New J. Chem., 2019,43, 19200-19207

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    Deciphering the mechanism of copper-catalyzed N-arylation between aryl halides and nitriles: a DFT study

    K. Ahmad, B. A. Khan, T. Akhtar, J. Khan and S. K. Roy, New J. Chem., 2019, 43, 19200
    DOI: 10.1039/C9NJ03860D

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