Abstract:

The transformation reactions of indole derivatives are fundamental knowledge in organic chemistry. Using electrons as clean reagents, electrochemistry serves as a sustainable alternative to traditional redox organic transformations and received considerable attention in recent years. In this study, 3-aryl indole was used as raw materials to realize dehydrogenation coupling and coupling-cyclization only by prolonging the electrolysis reaction time. The reaction runs under mild conditions and the reaction operation is simple and safe. The reaction is efficient to gain product in good yield and can be monitored by using thin-layer chromatography. There are various reaction phenomena for students to observe. Moreover, the final product of the reaction is controllable via simply tuning the reaction time. The experiment can be reproduced with similar efficiency after many times. All products are solid and can be purified via silica gel column chromatography. Nuclear magnetic resonance (NMR) spectroscopy and high resolution mass spectrometry (HRMS) were recorded to analyze the structure of products which also show different fluorescence properties. Based on the basic knowledge of indole transformation chemistry, this experiment uses green electrolysis strategies to develop practical synthesis methods for nitrogen-containing heterocyclic compounds, and guides students to learn interdisciplinary knowledge of organic synthesis chemistry and physical chemistry, establishes interdisciplinary knowledge awareness and pays attention to the frontiers of organic chemistry.

Key words: Indole derivatives, C―C coupling, Multi-step reaction, Electro-organic synthesis, Product-tunable reaction