College of Chemistry, Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), Renewable Energy Conversion and Storage Center (ReCAST), Shenzhen Research Institute, Frontiers Science Center for New Organic Matter, Nankai University, Tianjin 300071, China.
Haihe Laboratory of Sustainable Chemical Transformations, Tianjin 300192, China.
J Am Chem Soc. 2022 Sep 7;144(35):16184-16190. doi: 10.1021/jacs.2c07385. Epub 2022 Aug 12.
Oxidative C-H/N-H cross-coupling has emerged as an atom-economical method for the construction of C-N bonds. Conventional oxidative C-H/N-H coupling requires at least one of the following: high temperatures, strong oxidizers, transition metal catalysts, organic solvents, light, and electrochemical cells. In this study, by merely spraying the water solutions of the substrates into microdroplets at room temperature, we show a series of oxidative C-H/N-H coupling products that are strikingly produced in a spontaneous and ultrafast manner. The reactions are accelerated by six orders of magnitude compared to the same reactions in the bulk. It has been previously proposed by fluorescence microscopy and theory that the spontaneously generated electric field at the microdroplets peripheries can be in the ∼10 V/m range. Based on mass spectrometric analysis of key radical intermediates, we opine that the ultrahigh electric field catalytically oxidizes the substrates by removing an electron, which further promotes C/N coupling. Taken together, we anticipate that microdroplet chemistry will be an avenue rich in green opportunities of constructing C-heteroatom bonds.
氧化 C-H/N-H 交叉偶联已成为构建 C-N 键的一种原子经济方法。传统的氧化 C-H/N-H 偶联至少需要以下一种条件：高温、强氧化剂、过渡金属催化剂、有机溶剂、光和电化学电池。在这项研究中，我们仅需在室温下将底物的水溶液喷雾成微液滴，就可以以自发和超快的方式显著生成一系列氧化 C-H/N-H 偶联产物。与在本体中的相同反应相比，反应速度加快了六个数量级。先前的荧光显微镜和理论研究表明，在微液滴边缘自发产生的电场可以达到约 10 V/m 的范围。基于关键自由基中间体的质谱分析，我们推测超高压电场通过去除电子来催化氧化底物，从而进一步促进 C/N 偶联。综上所述，我们预计微液滴化学将为构建 C-杂原子键提供丰富的绿色机会。
