Aerobic oxychlorination of phenols catalyzed by copper(II) chloride

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• 作者：Luciano Menini and Elena V. Gusevskaya
• 关键词：Catalytic oxychlorination ; Phenols ; Dioxygen ; Copper chloride
• 刊名：Applied Catalysis A: General
• 出版年：2006
• 出版时间：17 July 2006
• 年：2006
• 卷：309
• 期：1
• 页码：122-128
• 全文大小：228 K

文摘

Oxychlorination of phenol and electron-rich phenolic compounds catalyzed by CuCl₂ under mild conditions has been developed. Chloride ions are used as halogenating agents and dioxygen as a final oxidant. The catalyst shows not only high regioselectivity for para- or ortho isomers but also a remarkable chemoselectivity for monochlorination, with no products of the oxidation of phenols being formed in detectable amounts. Non-phenolic aromatics and phenols with electron withdrawing substituents undergo no transformation at all under similar conditions. A free radical mechanism is suggested, which involves one-electron oxidation of phenol by CuCl₂ to the corresponding phenoxy radical followed by a rapid reaction of the tautomeric cyclohexadienyl radical with CuCl₂ resulting in chlorinated product and CuCl. Re-oxidation of CuCl by dioxygen completes a catalytic cycle. This simple, low cost and selective method might be applied for the synthesis of chlorophenols, which are widely used in pharmaceutical, agricultural and dye industries.