Synthesis and structures of gold and copper carbene intermediates in catalytic amination of alkynes.
Synthesis and structures of gold and copper carbene intermediates in catalytic amination of alkynes.
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炔烃催化胺化金铜卡宾中间体的合成与结构
DOI：
10.1038/ncomms14625
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发表时间：
2017-03-06
影响因子：
16.6
通讯作者：
Zhang J
中科院分区：
文献类型：
--
作者：
Wang J;Cao X;Lv S;Zhang C;Xu S;Shi M;Zhang J
金属卡宾通常被认为是后过渡金属催化炔烃转化中的反应中间体。然而，由于其高反应性，这些转化中金属卡宾中间体的分离和结构表征仍然未知。在此，我们报道了通过五外位环化在 Au(I) 或 Cu(I) 催化的 N-炔基甲脒环化中分离出两种无环金和铜卡宾中间体。 X射线衍射、13C NMR谱数据和计算分析为具有类碳正离子电子特征的金卡宾中间体的形成提供了证据。使用本征键轨道（IBO）方法，我们还评估了金卡宾中间体中卡宾碳原子上有机取代基的π稳定作用。另一种罕见的六元铜卡宾配合物也是通过6-endo-dig环化得到的。这些金属卡宾已被证明具有氧化活性。 N-炔基甲脒的金属促进环化提供了合成金属卡宾物种的简便方法。
Metal carbenes are often proposed as reactive intermediates in the late transition metal-catalysed transformations of alkynes. Owing to their high reactivity, however, isolation and structural characterization of metal carbene intermediates in these transformations has remained unknown. Herein, we report the isolation of two acyclic gold and copper carbene intermediates in either Au(I)- or Cu(I)-catalysed cyclization ofN-alkynyl formamidines through five-exo-dig cyclization. X-ray diffraction,13C NMR spectra data and computational analyses provide evidence for the formation of a gold carbene intermediate with a carbocation-like electronic character. Using the intrinsic bond orbital (IBO) approach, we also evaluate the π-stabilizing effects of organic substituents at the carbene carbon atom in the gold carbene intermediate. Another rare six-membered copper carbene complex is also obtained through 6-endo-dig cyclization. These metal carbenes have proven reactive toward oxidation. The metal-promoted cyclization ofN-alkynyl formamidine provides a facile approach to synthesize metal carbene species.