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铜催化硫乙酸与芳基卤化物的 C-S 交叉偶联反应的机理研究:实验-计算联合研究。

Mechanistic Insight into the Cu-Catalyzed C-S Cross-Coupling of Thioacetate with Aryl Halides: A Joint Experimental-Computational Study.

机构信息

Departamento de Química Orgánica, Facultad de Ciencias Químicas, INFIQC, Universidad Nacional de Córdoba, CONICET , X5000HUA Córdoba, Argentina.

Philipps-Universität Marburg, Fachbereich Chemie , Hans-Meerwein straße 4, 35032 Marburg, Germany.

出版信息

J Org Chem. 2017 Nov 3;82(21):11464-11473. doi: 10.1021/acs.joc.7b01991.

Abstract

The mechanism of the Ullmann-type reaction between potassium thioacetate (KSAc) and iodobenzene (PhI) catalyzed by CuI associated with 1,10-phenanthroline (phen) as a ligand was explored experimentally and computationally. The study on C-S bond formation was investigated by UV-visible spectrophotometry, cyclic voltammetry, mass spectrometry, and products assessment from radical probes. The results indicate that under experimental conditions the catalytically active species is [Cu(phen)(SAc)] regardless of the copper source. An examination of the aryl halide activation mechanism using radical probes was undertaken. No evidence of the presence of radical species was found during the reaction process, which is consistent with an oxidative addition cross-coupling pathway. The different reaction pathways leading to the experimentally observed reaction products were studied by DFT calculation. The oxidative addition-reductive elimination mechanism via an unstable Cu intermediate is energetically more feasible than other possible mechanisms such as single electron transfer, halogen atom transfer, and σ-bond methatesis.

摘要

实验和计算研究了碘化亚铜(CuI)与 1,10-菲咯啉(phen)配位,催化硫代乙酸钾(KSAc)与碘苯(PhI)之间的Ullmann 型反应的机理。通过紫外-可见分光光度法、循环伏安法、质谱法以及自由基探针评估产物研究了 C-S 键形成。结果表明,在实验条件下,无论铜源如何,催化活性物质都是[Cu(phen)(SAc)]。使用自由基探针对芳基卤化物活化机理进行了考察。在反应过程中未发现自由基存在的证据,这与氧化加成交叉偶联途径一致。通过 DFT 计算研究了导致实验观察到的反应产物的不同反应途径。通过不稳定的 Cu 中间体进行的氧化加成-还原消除机理在能量上比其他可能的机理(如单电子转移、卤原子转移和σ键均裂)更可行。

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