Insight into the Mechanism of the CuAAC Reaction by Capturing the Crucial Au4Cu4–π-Alkyne Intermediate,Journal of the American Chemical Society

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Insight into the Mechanism of the CuAAC Reaction by Capturing the Crucial Au4Cu4–π-Alkyne Intermediate
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2021-01-22 , DOI: 10.1021/jacs.0c12498
Yaping Fang _{1,

2} , Kang Bao _{1,

2} , Peng Zhang ₃ , Hongting Sheng _{1,

2} , Yapei Yun _{1,

2} , Shu-Xian Hu ₃ , Didier Astruc ₄ , Manzhou Zhu _{1,

2}

Affiliation

The classic Fokin mechanism of the CuAAC reaction of terminal alkynes using a variety of Cu(I) catalysts is well-known to include alkyne deprotonation involving a bimetallic σ,π-alkynyl intermediate. In this study, we have designed a CNT-supported atomically precise nanocluster Au4Cu4 (noted Au4Cu4/CNT) that heterogeneously catalyzes the CuAAC reaction of terminal alkynes without alkyne deprotonation to a σ,π-alkynyl intermediate. Therefore, three nanocluster-π-alkyne intermediates [Au4Cu4(π-CH≡C-p-C6H4R)], R = H, Cl, and CH3, have been captured and characterized by MALDI-MS. This Au4Cu4/CNT system efficiently catalyzed the CuAAC reaction of terminal alkynes, and internal alkynes also undergo this reaction. DFT results further confirmed that HC≡CPh was activated by π-complexation with Au4Cu4, unlike the classic dehydrogenation mechanism involving the bimetallic σ,π-alkynyl intermediate. On the other hand, a Cu11/CNT catalyst was shown to catalyze the reaction of terminal alkynes following the classic deprotonation mechanism, and both Au11/CNT and Cu11/CNT catalysts were inactive for the AAC reaction of internal alkynes under the same conditions, which shows the specificity of Au4Cu4 involving synergy between Cu and Au in this precise nanocluster. This will offer important guidance for subsequent catalyst design.

中文翻译：

通过捕获关键的 Au4Cu4–π-炔中间体深入了解 CuAAC 反应的机制

众所周知，使用各种 Cu(I) 催化剂的末端炔烃的 CuAAC 反应的经典 Fokin 机制包括炔烃去质子化，涉及双金属 σ,π-炔基中间体。在这项研究中，我们设计了一种由 CNT 支持的原子级精确纳米团簇 Au4Cu4（记为 Au4Cu4/CNT），该纳米团簇可异质催化末端炔烃的 CuAAC 反应，而无需炔烃去质子化为 σ,π-炔基中间体。因此，三种纳米簇-π-炔中间体 [Au4Cu4(π-CH≡Cp-C6H4R)]，R = H、Cl 和 CH3，已被 MALDI-MS 捕获并表征。该 Au4Cu4/CNT 体系有效地催化了末端炔烃的 CuAAC 反应，内部炔烃也进行了该反应。DFT 结果进一步证实了 HC≡CPh 通过与 Au4Cu4 的 π 络合而被激活，与涉及双金属 σ,π-炔基中间体的经典脱氢机制不同。另一方面，Cu11/CNT 催化剂显示出遵循经典的去质子化机制催化末端炔烃的反应，并且 Au11/CNT 和 Cu11/CNT 催化剂在相同条件下对内部炔烃的 AAC 反应均无活性，这显示了 Au4Cu4 的特异性，涉及该精确纳米团簇中 Cu 和 Au 之间的协同作用。这将为后续催化剂设计提供重要指导。这显示了 Au4Cu4 的特异性，涉及该精确纳米团簇中 Cu 和 Au 之间的协同作用。这将为后续催化剂设计提供重要指导。这显示了 Au4Cu4 的特异性，涉及该精确纳米团簇中 Cu 和 Au 之间的协同作用。这将为后续催化剂设计提供重要指导。

更新日期：2021-01-22

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