Nitrogen‐containing six‐membered heterocycles such as pyridines, pyrimidines, and triazines are widely used in the synthesis of natural products and pharmaceuticals. Recently, a promising approach to these structures via [2+2+2] cycloadditions of alkynes and nitriles has been developed. Transition‐metal complex catalysts play key roles in the regio‐, chemo‐, or stereo‐selectivity of transformations. Here, we summarize recent advances in metal‐mediated/catalyzed [2+2+2] cycloadditions for synthesizing pyridines and pyrimidines. We also describe progress in triazine synthesis via metal‐mediated/catalyzed nitrile cyclotrimerization.

中文翻译：

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[2 + 2 + 2]环加成反应的过渡金属介导/催化合成吡啶，嘧啶和三嗪

含氮六元杂环（例如吡啶，嘧啶和三嗪）广泛用于天然产物和药物的合成。最近，已经开发了通过炔烃和腈的[2 + 2 + 2]环加成反应来制备这些结构的有前途的方法。过渡金属络合物催化剂在区域，化学或立体选择性的转化中起关键作用。在这里，我们总结了在金属介导的/催化的[2 + 2 + 2]环加成反应中用于合成吡啶和嘧啶的最新进展。我们还描述了通过金属介导的/催化的腈环三聚反应合成三嗪的进展。