Asymmetric Electrooxidation of Indoles: Mechanistic Insights from an Enantioselective Bromoradical Addition Pathway
Changdi Zheng1, Yanjun Wan1, Yuhua Chen1
1Key Laboratory for Green Pharmaceutical Technologies and Related Equipment of Ministry of Education, College of Pharmaceutical Sciences, Zhejiang University of Technology, Hangzhou 310014, People's Republic of China.
Abstract:
Oxidative rearrangement of tetrahydro-β-carbolines (THβCs) represents a straightforward route to the synthesis of spirooxindoles. Herein, we disclose the first bromoradical (Br•)-initiated enantioselective electrooxidative rearrangement of THβCs, leading to highly enantioenriched spirooxindoles. Mechanistically, asymmetric Br• addition to THβCs initiates the reaction, distinguishing this process from established pathways induced by either halogen cations (X+) or single-electron transfer (SET). Successful trapping of the key radical intermediate provides explicit evidence of this unprecedented Br•-mediated mechanism.
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