Publication: Aryl C-O oxidative addition of phenol derivatives to nickel supported by an N-heterocyclic carbene: Via a Ni five-centered complex
Issued Date
2019-01-01
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ISSN
14779234
14779226
14779226
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2-s2.0-85066831726
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Mahidol University
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SCOPUS
Bibliographic Citation
Dalton Transactions. Vol.48, No.22 (2019), 7817-7827
Suggested Citation
Chayapat Uthayopas, Panida Surawatanawong Aryl C-O oxidative addition of phenol derivatives to nickel supported by an N-heterocyclic carbene: Via a Ni five-centered complex. Dalton Transactions. Vol.48, No.22 (2019), 7817-7827. doi:10.1039/c9dt00455f Retrieved from: https://repository.li.mahidol.ac.th/handle/123456789/50585
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Title
Aryl C-O oxidative addition of phenol derivatives to nickel supported by an N-heterocyclic carbene: Via a Ni five-centered complex
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Abstract
© The Royal Society of Chemistry 2019. Phenol derivatives have been increasingly used as alternatives for aryl halides in cross-coupling reactions due to their lower toxicity and easier availability. Nickel complexes have been developed as efficient catalysts for aryl C-O bond activation of phenol derivatives. Herein, we performed a density functional study to investigate the aryl C-O bond oxidative addition of phenol derivatives on Ni-SIPr. For phenyl sulfonates and phenyl esters, the pathway via a five-centered transition state involving the interaction from sulfonyl/carbonyl O to Ni is preferred over that via a three-centered transition state. While the five-centered transition state with the interaction from sulfamoyl N to Ni is favored over the interaction from sulfamoyl O to Ni for phenyl sulfamate, the interaction from carbamoyl O to Ni is more favored for phenyl carbamate. For aryl ethers, the Lewis acid AlMe3 facilitates aryl C-O bond activation by forming a Lewis acid/base adduct with 2-methoxynaphthalene (NaphOMe) resulting in a lower free energy barrier than that in the absence of AlMe3. While the free energy barriers for the aryl C-O bond oxidative addition of a NaphOMe/AlMe2R (R = Me, Ph, OMe, and H) adduct via the "classical" three-centered transition state are all similar, the corresponding free energy barriers via the five-centered transition state, involving the interaction from the R group of AlMe2R to Ni, can be lower and depend on the R group. Not only is the aryl C-O bond weakened, but the nucleophilicity of Ni is enhanced in the latter pathway. In fact, these key interactions are analogous to those via the five-centered transition states of phenyl sulfonate/sulfamate and phenyl ester/carbamate. Our results revealed that the pathway involving an additional electron donating interaction to Ni via the five-centered transition state facilitates the aryl C-O bond oxidative addition of phenol derivatives. Through this pathway, the appropriate use of organoaluminum can improve the efficiency of Ni catalysts for cross-coupling reactions of inert aryl ethers.