The transition‐metal‐catalyzed direct synthesis of amides from alcohols and amines is herein demonstrated as a highly environmentally benign and atom‐economic process. Among various catalyst systems, in situ generated N‐heterocyclic carbene (NHC)‐based ruthenium (Ru) halide catalyst systems have been proven to be active for this transformation. However, these existing catalyst systems usually require an additional ligand to achieve satisfactory results. In this work, through extensive screening of a diverse variety of NHC precursors, we discovered an active in situ catalyst system for efficient amide synthesis without any additional ligand. Notably, this catalyst system was found to be insensitive to the electronic effects of the substrates, and various electron‐deficient substrates, which were not highly reactive with our previous catalyst systems, could be employed to afford the corresponding amides efficiently. Furthermore, mechanistic investigations were performed to provide a rationale for the high activity of the optimized catalyst system. NMR‐scale reactions indicated that the rapid formation of a Ru hydride intermediate (signal at δ=−7.8 ppm in the ¹H NMR spectrum) after the addition of the alcohol substrate should be pivotal in establishing the high catalyst activity. Besides, HRMS analysis provided possible structures of the in situ generated catalyst system.

中文翻译：

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带有多种N-杂环碳前体的原位生成钌催化剂体系，用于从醇和胺合成原子-经济酰胺

本文证明了由醇和胺进行的过渡金属催化酰胺的直接合成是一种对环境有益且原子经济的过程。在各种催化剂体系中，已证明原位生成的基于N-杂环卡宾（NHC）的卤化钌（Ru）催化剂体系对于这种转化是有效的。然而，这些现有的催化剂体系通常需要额外的配体以获得令人满意的结果。在这项工作中，通过广泛筛选各种NHC前体，我们发现了一种有效的酰胺合成活性原位催化剂体系，而无需任何其他配体。值得注意的是，发现该催化剂体系对基质和各种电子不足的基质的电子效应不敏感，与我们以前的催化剂体系不具有高反应活性的化合物，可以用来有效地提供相应的酰胺。此外，进行了机械研究以为优化的催化剂体系的高活性提供理论依据。NMR规模反应表明，氢化钌中间体迅速形成（添加醇底物后，在¹ H NMR光谱中的δ = -7.8 ppm对于建立高催化剂活性至关重要。此外，HRMS分析提供了原位生成的催化剂体系的可能结构。