Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology (Ministry of Education), Tsinghua University , Beijing 100084, China.
J Am Chem Soc. 2014 Apr 30;136(17):6326-32. doi: 10.1021/ja412615h. Epub 2014 Apr 22.
Copper and its salts are abundant, inexpensive, and eco-friendly and have been used as the surrogates of noble metals to effect arene C-H bond activation and transformations. Despite of the recent significant progress of the study, syntheses of high-valent arylcopper(II-III) compounds are still very rare and mechanisms of copper(II)-catalyzed reactions remain elusive. With the use of azacalix[1]arene[3]pyridines as a platform, a number of arylcopper(II) compounds were synthesized efficiently from the reaction of Cu(ClO4)2 under ambient conditions. The resulting aryl-Cu(II) compounds, which contain an unprecedented (substituted) phenyl-Cu(II) σ-bond, were stable under atmospheric conditions and can undergo facile oxidation reaction by free copper(II) ions or oxone to afford arylcopper(III) compounds in good yields. Both arylcopper(II) and arylcopper(III) compounds were characterized unambiguously by means of XRD, XPS, and NMR methods. Experimental evidence including reaction kinetics, LFER and KIE, and theoretical calculations indicated that the Cu(ClO4)2-mediated arene C-H bond activation proceeds plausibly through an electrophilic aromatic metalation pathway. The synthesis of high-valent arylcopper compounds and the reaction mechanism reported here highlight the diversity and richness of organocopper chemistry.
铜及其盐类丰富、廉价且环保，一直被用作贵金属的替代品，以实现芳环 C-H 键的活化和转化。尽管最近在该领域的研究取得了显著进展，但高价芳基铜(II-III)化合物的合成仍然非常罕见，铜(II)催化反应的机制也难以捉摸。本研究以氮杂杯[1]芳烃[3]吡啶为平台，在常温常压条件下，通过 Cu(ClO4)2 反应高效合成了一系列芳基铜(II)化合物。所得的芳基-Cu(II)化合物含有前所未有的（取代）苯基-Cu(II)σ键，在大气条件下稳定，可通过自由铜(II)离子或 Oxone 发生容易的氧化反应，以良好的收率得到芳基铜(III)化合物。芳基铜(II)和芳基铜(III)化合物均通过 XRD、XPS 和 NMR 方法进行了明确的表征。包括反应动力学、LFER 和 KIE 以及理论计算在内的实验证据表明，Cu(ClO4)2 介导的芳环 C-H 键活化可能通过亲电芳香金属化途径进行。这里报道的高价芳基铜化合物的合成和反应机制突出了有机铜化学的多样性和丰富性。
