Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, The Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
School of Future Technology, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China.
J Am Chem Soc. 2022 Sep 14;144(36):16667-16675. doi: 10.1021/jacs.2c07450. Epub 2022 Sep 1.
Singlet oxygen (O)-mediated oxidation represents an attractive strategy for incorporation of oxygen atoms from air under mild and environmentally benign conditions. However, the O reaction with enamine suffers from fragmentation, leading to very unsuccessful transformation. Here, Lewis acid is introduced to intercept [2 + 2] or "ene" reaction intermediates of the O reaction and enables oxidative dimerization of enamines to produce pyrrolin-4-ones in good to excellent yields. Mechanistic studies reveal the formation of the imino ketone intermediate from the interaction of O and enamine, which is able to interact with Lewis acid, relaying the O reaction in enamine chemistry. For the first time, selective cross-dimerization of two different enamines is achieved. Due to the advantages of mild conditions, high chemoselectivity, and up to 99% yield, a promising strategy has been developed for synthesizing aza-heterocycles under ambient conditions, which can be further applied for the synthesis of imidazolone, quinoxaline, and highly functionalized imine.
单线态氧（O）介导的氧化代表了一种在温和且环境友好的条件下从空气中引入氧原子的有吸引力的策略。然而，O 与烯胺的反应会发生碎片化，导致转化非常不成功。在这里，引入路易斯酸来拦截 O 反应的 [2+2] 或“ene”反应中间体，并使烯胺发生氧化二聚化，以良好到优异的收率生成吡咯啉-4-酮。机理研究表明，O 和烯胺相互作用形成亚氨基酮中间体，它能够与路易斯酸相互作用，在烯胺化学中传递 O 反应。这是首次实现两种不同烯胺的选择性交叉二聚化。由于条件温和、高化学选择性和高达 99%的产率的优势，已经开发出了一种在环境条件下合成氮杂杂环的有前途的策略，该策略可进一步应用于咪唑啉酮、喹喔啉和高度官能化亚胺的合成。
