Previous Article Next Article Articles ASAP Direct Hydroxylation of Benzene to Phenol Using Hydrogen Peroxide Catalyzed by Nickel Complexes Supported by Pyridylalkylamine Ligands

Yuma Morimoto , Shuji Bunno , Nobutaka Fujieda , Hideki Sugimoto , and Shinobu Itoh ^*

Department of Material and Life Science, Division of Advanced Science and Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan

J. Am. Chem. Soc., Article ASAP

DOI: 10.1021/jacs.5b01814

Selective hydroxylation of benzene to phenol has been achieved using H₂O₂ in the presence of a catalytic amount of the nickel complex [Ni^II(tepa)]²⁺ (2) (tepa = tris[2-(pyridin-2-yl)ethyl]amine) at 60 °C. The maximum yield of phenol was 21% based on benzene without the formation of quinone or diphenol. In an endurance test of the catalyst, complex 2 showed a turnover number (TON) of 749, which is the highest value reported to date for molecular catalysts in benzene hydroxylation with H₂O₂. When toluene was employed as a substrate instead of benzene, cresol was obtained as the major product with 90% selectivity. When H₂¹⁸O₂ was utilized as the oxidant, ¹⁸O-labeled phenol was predominantly obtained. The reaction rate for fully deuterated benzene was nearly identical to that of benzene (kinetic isotope effect = 1.0). On the basis of these results, the reaction mechanism is discussed.

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