Application of Indazolin-3-ylidenes in Catalysis: Steric Tuning of Nonclassical Formally Normal N -Heterocyclic Carbenes with Dual Electronic Character for Catalysis
Application of Indazolin-3-ylidenes in Catalysis: Steric Tuning of Nonclassical Formally Normal N -Heterocyclic Carbenes with Dual Electronic Character for Catalysis
复制标题
吲唑啉-3-亚基在催化中的应用：具有双电子特征的非经典形式正构N-杂环卡宾的空间调节催化
DOI：
10.1021/acs.organomet.2c00140
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发表时间：
2022
期刊：
影响因子：
2.8
通讯作者：
Szostak, Michal
中科院分区：
文献类型：
--
作者：
Zhang, Jin;Wang, Yue;Zhang, Yuting;Liu, Ting;Fang, Shuai;Wang, Ruihong;Ma, Yangmin;Fang, Ran;Szostak, Roman;Szostak, Michal
n -杂环碳（NHCs）是化学和催化中的关键配体，是研究金属中心反应活性的重要工具。特别是非经典非杂原子稳定的n -杂环碳化合物（NHCs）由于具有较高的配体碱度而引起了广泛的关注。然而，非经典NHCs的催化活性研究一直面临挑战，因为其对催化作用至关重要的空间环境的修饰受到限制。在此，我们报道了一类新的茚唑啉-3-芳基配体，它是由现成的茚唑衍生的，具有围绕金属中心的立体分化特征。与经典的咪唑-2-吡啶相比，这些配体由于其中一个氮原子的重新定位而具有很强的σ给能性。同时，融合芳环的存在使其接受π的性质得到了明显增强。与经典的咪唑-2-酰亚胺配体相比，vburi %更高。我们证明了当用作配体时，咪唑啉-3-炔基的立体分化配位环境有效地促进了炔烃的氢胺化反应，从而获得了有价值的含氮基序，从而击败了经典的咪唑-2-炔基。该方案也已应用于具有挑战性的炔的氢化反应，并应用于后期多样化。对其进行了综合表征、配位化学以及立体、供σ、接π等性能的评价。计算研究，以深入了解反应机制的报道。我们预计，立体分化的非经典吲哚啉-3-吡啶将加速过渡金属催化中定义明确的杂原子稳定性较低的n-杂环碳配体的发展。
N-Heterocyclic carbenes (NHCs) are pivotal ligands in chemistry and catalysis, providing essential tools for the reactivity of metal centers. In particular, the development of nonclassical less heteroatom-stabilizedN-heterocyclic carbenes (NHCs) has attracted tremendous attention owing to higher ligand basicity. However, research on the catalytic activity of nonclassical NHCs has been challenging due to restrictions in modifying steric environment crucial for catalysis. Herein, we report a new class of indazolin-3-ylidene ligands derived from readily available indazole that feature steric differentiation around the metal center. Compared to classical imidazol-2-ylidenes, these ligands feature strongly enhanced σ-donation resulting from re-positioning of one of the nitrogen atoms. Simultaneously, the presence of the fused aromatic ring results in strongly enhanced π-accepting properties. The % Vburis higher than the classic imidazol-2-ylidene IMes ligand. We demonstrate that when used as ligands, the sterically differentiated coordination environment of indazolin-3-ylidenes efficiently promote the hydroamination reaction of alkynes to give valuable nitrogen-containing motifs, outcompeting the classical imidazol-2-ylidenes. This protocol has also been applied to the challenging hydrohydrazination of alkynes and applied to the late-stage diversification. Comprehensive characterization, coordination chemistry, as well as the evaluation of steric, σ-donating, and π-accepting properties are demonstrated. Computational studies to gain insight into the reaction mechanism are reported. We anticipate that sterically differentiated nonclassical indazolin-3-ylidenes will accelerate the development of well-defined less heteroatom-stabilizedN-heterocyclic carbene ligands in transition-metal catalysis.