Radical Reactivity, Catalysis, and Reaction Mechanism of Arylcopper(II) Compounds: The Missing Link in Organocopper Chemistry
Radical Reactivity, Catalysis, and Reaction Mechanism of Arylcopper(II) Compounds: The Missing Link in Organocopper Chemistry
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芳基铜(II)化合物的自由基反应性、催化作用和反应机理：有机铜化学中缺失的环节
DOI：
10.1021/jacs.9b10226
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发表时间：
2019-11-13
影响因子：
15
通讯作者：
Wang, Mei-Xiang
中科院分区：
文献类型：
--
作者：
Zhang, Qian;Wang, Ting;Wang, Mei-Xiang
有机铜(I)化合物被认为是碳亲核试剂，而有机铜(III)络合物作为中间体参与铜催化，与各种阴离子亲核试剂发生交叉偶联反应。与有机铜(I)和(III)化合物的化学不同，有机铜(II)化学实际上是整体有机铜化学中缺失的一环，因为结构明确的有机铜(II)化合物几乎没有被分离或研究。本文报道了从大环氮杂杯[1]芳烃[3]吡啶与铜(ClO4)(2)的芳烃C-H键反应中得到的稳定且结构明确的芳基铜(II)化合物的自由基反应。我们发现芳基铜(II)化合物作为基本自由基物种与自由基引发剂2，2‘-偶氮二异丁腈(AIBN)或2，2’-偶氮二(2，4-二甲基戊腈)(ABVN)和α，β-不饱和化合物CH2=CHX(X=CO2CH3，CN，CONH2，COCH3和SO2Ph)进行有效的三组分反应，得到多官能化产物。实验和理论相结合的研究表明，自由基直接与芳基铜(II)的C-芳基原子偶联，形成C-烷基-C-芳基键，其机理为Cu(II)/Cu(I)。对芳基铜(II)化合物的形成和自由基活性的理解使得铜催化的芳烃C-H键功能化的三组分自由基反应得以发展。
Organocopper(I) compounds are recognized as carbon nucleophiles, while organocopper(III) complexes are involved in copper catalysis as intermediates to undergo a cross-coupling reaction with various anionic nucleophiles. In contrast to the chemistry of organocopper(I) and (III) compounds, organocopper(II) chemistry is virtually a missing link in integral organocopper chemistry because structurally well-defined organocopper(II) compounds have barely been isolated or studied. We report in this Article an investigation of the radical reactions of stable and structurally well-defined arylcopper(II) compounds, obtained readily from the arene C-H bond reaction of macrocyclic azacalix[1]arene[3]pyridines and Cu(ClO4)(2). We have found that arylcopper(II) compounds acted as essentially radical species to undergo an efficient three-component reaction with radical initiators 2,2'-azobis(isobutyronitrile) (AIBN) or 2,2'-azobis(2,4-dimethylvaleronitrile) (ABVN) and alpha,beta-unsaturated compounds CH2=CHX (X = CO2CH3, CN, CONH2, COCH3, and SO2Ph) to afford polyfunctionalized products. Combined experimental and theoretical studies revealed that radicals couple directly with the C-aryl atom of arylcopper(II) compounds to form C-alkyl-C-aryl bonds through a Cu(II)/Cu(I) mechanism. Comprehension of the formation and radical reactivity of arylcopper(II) compounds has allowed the development of a copper-catalyzed three-component radical reaction for arene C-H bond functionalization.