Robust Cobalt Catalyst for Nitrile/Alkyne [2+2+2] Cycloaddition: Synthesis of Polyarylpyridines and Their Mechanochemical Cyclodehydrogenation to Nitrogen‐Containing Polyaromatics**
作者:Chang‐Sheng Wang、Qiao Sun、Felipe García、Chen Wang、Naohiko Yoshikai
DOI:10.1002/anie.202017220
日期:2021.4.19
the reactants. Thus, examples of efficient, fully intermolecular catalytic [2+2+2] pyridine synthesis, especially those employing unactivated nitriles and internal alkynes leading to pentasubstituted pyridines, remain scarce. Herein, we report on simple and inexpensive catalytic systems based on cobalt(II) iodide, 1,3‐bis(diphenylphosphino)propane, and Zn that promote [2+2+2] cycloaddition of various
腈和炔烃的过渡金属催化[2 + 2 + 2]环加成反应是吡啶的公认合成方法。然而,这些环加成通常依赖于使用束缚的二炔或氰基炔作为反应物之一。因此,仍然缺乏有效的,完全分子间催化的[2 + 2 + 2]吡啶合成的例子,尤其是那些使用未活化的腈和内部炔烃生成五取代的吡啶的例子。在此,我们报告了一种简单廉价的催化体系,该体系基于碘化钴(II),1,3-双(二苯基膦基)丙烷和锌,可促进各种腈和二芳基乙炔的[2 + 2 + 2]环加成反应,从而合成a范围广泛的聚芳基吡啶。DFT研究支持涉及两个炔烃氧化偶联,腈插入钴环戊二烯的反应途径,和C‐N还原消除。所得的四芳基和五芳基吡啶通过机械化学辅助的多重还原性环脱氢作用,成为迄今为止前所未有的含氮多环芳烃的前体。