韩国科学技术院Sukbok Chang团队报道了钴催化的未活化烷烃分子间C-H酰胺化反应。 相关研究成果于2021年3月29日发表在《美国化学会杂志》。

烷烃是丰富而廉价的碳氢化合物来源，因此，开发将碳氢化合物原料转化为高附加值化学品的新方法具有重要意义。然而，由于碳-氢键的固有惰性，以直接和选择性的方式实现这种转变是一个挑战。

该文报道了一种定制的Cp*Co（III）（LX）催化的高效和位点可选择的包含轻烷烃的未活化烃类分子间酰胺化反应。钴配合物的电子调制提高了酰胺化效率，并且通过对预先假定的类硝基苯钴物种的FMO分析，从理论上解释了这些效应。在目前的钴方案下，在各种非活性烷烃中观察到次级C–H键选择性，以逆转固有的三级偏好，这归因于钴系统的空间需求，同时给获得三级C–H键带来了困难。

实验和计算研究表明，假定的三重态Co-硝基烯通过类似自由基的吸氢途径转移到烷烃的C-H键上。

附：英文原文

Title: Cobalt-Catalyzed Intermolecular C–H Amidation of Unactivated Alkanes

Author: Jeonghyo Lee, Seongho Jin, Dongwook Kim, Soon Hyeok Hong, Sukbok Chang

Issue&Volume: March 29, 2021

Abstract: Alkanes are an abundant and inexpensive source of hydrocarbons; thus, development of new methods to convert the hydrocarbon feedstocks to value-added chemicals is of high interest. However, it is challenging to achieve such transformation in a direct and selective manner mainly due to the intrinsic inertness of their C–H bonds. We herein report a tailored Cp*Co(III)(LX)-catalyzed efficient and site-selective intermolecular amidation of unactivated hydrocarbons including light alkanes. Electronic modulation of the cobalt complexes led to the enhanced amidation efficiency, and these effects were theoretically rationalized by the FMO analysis of presupposed cobalt nitrenoid species. Under the current cobalt protocol, a secondary C–H bond selectivity was observed in various nonactivated alkanes to reverse the intrinsic tertiary preference, which is attributed to the steric demands of the cobalt system that imposes difficulties in accessing tertiary C–H bonds. Experimental and computational studies suggested that the putative triplet Co nitrenoids are transferred to the C–H bonds of alkanes via a radical-like hydrogen abstraction pathway.

DOI: 10.1021/jacs.1c01524

Source: https://pubs.acs.org/doi/10.1021/jacs.1c01524