Well-defined, air- and moisture-stable palladium–imidazo[1,5- a ]pyridin-3-ylidene complexes: a versatile catalyst platform for cross-coupling reactions by L-shaped NHC ligands
Well-defined, air- and moisture-stable palladium–imidazo[1,5- a ]pyridin-3-ylidene complexes: a versatile catalyst platform for cross-coupling reactions by L-shaped NHC ligands
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结构明确、空气和湿气稳定的钯-咪唑并[1,5-a]吡啶-3-亚基配合物：用于 L 形 NHC 配体交叉偶联反应的多功能催化剂平台
DOI：
10.1039/d2cy01136k
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发表时间：
2022
影响因子：
5
通讯作者：
Szostak, Michal
中科院分区：
文献类型：
--
作者：
Zhou, Tongliang;Gao, Pengcheng;Bisz, Elwira;Dziuk, Błażej;Lalancette, Roger;Szostak, Roman;Szostak, Michal
我们描述了[（NHC）Pd（肉桂基）Cl]配合物的ImPy（ImPy =咪唑并[1，5-a]吡啶-3-亚基）作为一种通用的交叉偶联反应的预催化剂类的发展。这些预催化剂的特征在于在刚性咪唑并[1，5-a]吡啶-3-亚基模板中以1：1的Pd与配体比率快速活化成单配体Pd（0）。 在催化剂框架的催化口袋中C5-取代基和N2-翼尖的空间匹配导致发现ImPyMesDipp作为高反应性咪唑并[1，5-a]吡啶-3-亚基配体，用于通过挑战C-NO2活化的Pd催化的硝基芳烃的交叉偶联。动力学研究表明这类定义明确的ImPy-Pd催化剂的快速活化和高反应性。结构研究提供了这类新的咪唑并[1，5-a]吡啶-3-亚基配体的全部特征。计算研究建立了空间受限的咪唑并[1，5-a]吡啶-3-亚基配体的电子性质。最后，公开了通过Ni催化的Kumada交叉偶联可规模化合成C5-取代的咪唑并[1，5-a]吡啶-3-亚基配体。该方法避免了在任何步骤中的色谱纯化，导致容易和模块化地接近ImPy配体。我们预计，定义明确的[Pd-ImPy]配合物将在有机合成和催化活化非反应性键中找到广泛的用途。
We describe the development of [(NHC)Pd(cinnamyl)Cl] complexes of ImPy (ImPy = imidazo[1,5-a]pyridin-3-ylidene) as a versatile class of precatalysts for cross-coupling reactions. These precatalysts feature fast activation to monoligated Pd(0) with 1 : 1 Pd to ligand ratio in a rigid imidazo[1,5-a]pyridin-3-ylidene template. Steric matching of the C5-substituent and N2-wingtip in the catalytic pocket of the catalyst framework led to the discovery of ImPyMesDipp as a highly reactive imidazo[1,5-a]pyridin-3-ylidene ligand for Pd-catalyzed cross-coupling of nitroarenes by challenging C–NO2 activation. Kinetic studies demonstrate fast activation and high reactivity of this class of well-defined ImPy–Pd catalysts. Structural studies provide full characteristics of this new class of imidazo[1,5-a]pyridin-3-ylidene ligands. Computational studies establish electronic properties of sterically-restricted imidazo[1,5-a]pyridin-3-ylidene ligands. Finally, a scalable synthesis of C5-substituted imidazo[1,5-a]pyridin-3-ylidene ligands through Ni-catalyzed Kumada cross-coupling is disclosed. The method obviates chromatographic purification at any of the steps, resulting in a facile and modular access to ImPy ligands. We anticipate that well-defined [Pd–ImPy] complexes will find broad utility in organic synthesis and catalysis for activation of unreactive bonds.