NHC-Stabilized Radicals in the Formal Hydroacylation Reaction of Alkynes
NHC-Stabilized Radicals in the Formal Hydroacylation Reaction of Alkynes
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DOI：
10.1002/ejoc.201801185
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发表时间：
2018-11
影响因子：
2.8
通讯作者：
J. Phan;Stephanie-M. Ruser;K. Zeitler;J. Rehbein
中科院分区：
文献类型：
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作者：
J. Phan;Stephanie-M. Ruser;K. Zeitler;J. Rehbein
N-杂环卡宾（NHC）催化的转化机制细节目前引起了人们的极大兴趣，其目标是操作中的活性催化剂以及关键中间体的结构和反应性问题。这些机理研究的驱动因素是需要了解催化剂系统的细微变化对其反应性的巨大影响，以及澄清经典催化循环中难以捉摸的中间体的情况。在醛的活化过程中，烯醇结构的形成，即布雷斯洛中间体，已被广泛接受。然而，此前我们可以证明，这种烯胺醇除了其离子反应途径外，还可以通过与起始材料进行氧化还原过程来遵循自由基途径。在本研究中，我们的目的是阐明这些自由基途径是否是一种更普遍的现象，特别是在炔烃的正式加氢酰化反应中。对自由基物种的观察以及对自由基和离子途径中关键元素步骤的计算分析可能会导致基于 NHC 稳定碳自由基的化学的进一步发展。
Mechanistic details of transformations catalyzed by N‐heterocyclic carbenes (NHC) are currently of great interest, targeting questions on the active catalyst in operation and the structure and reactivity of key intermediates. These mechanistic studies are driven by the need to understand the big impact of subtle changes on the catalyst system on its reactivity, as well as to clarify the situation around the elusive intermediates in the classical catalytic cycle. In the activation process of aldehydes the formation of an enaminol structure, coined the Breslow intermediate, is widely accepted. Previously, however, we could prove that this enaminol has, besides its ionic reaction pathway, also the option to follow a radical pathway, by undergoing redox processes with the starting material. In the present study we aim to elucidate if these radical pathways are a more general phenomenon, specifically in the formal hydroacylation reaction of alkynes. The observation of radical species and computational analysis of key elemental steps in the radical and ionic pathways may lead to an onward development of chemistry based on NHC‐stabilized carbon radicals.