Catalyst‐ and Reagent‐Free Formal Aza‐Wacker Cyclizations Enabled by Continuous‐Flow Electrochemistry

• Published in: Angewandte Chemie International Edition Vol. 60; no. 20; pp. 11237 - 11241
• Main Authors: Huang, Chong, Li, Zhao‐Yu, Song, Jinshuai, Xu, Hai‐Chao
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 10-05-2021
• Edition: International ed. in English
• Subjects: Additives; Alkenes; Bioactive compounds; Catalysts; Chemical reactions; Chemical synthesis; continuous flow; cyclization; Electrochemistry; heterocycles; Natural products; radical reactions; Reagents; Sustainable development; radical reactions; continuous flow; electrochemistry; heterocycles; cyclization
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202101835

The development of efficient and sustainable methods to access saturated N‐heterocycles is of great importance because of the prevalence of these structures in natural products and bioactive compounds. Pd‐catalyzed aza‐Wacker type cyclization is a powerful method and provides access to N‐heterocycles bearing an alkene moiety available for further synthetic manipulations from readily available materials. Herein we disclose a catalyst‐ and reagent‐free formal aza‐Wacker type cyclization reaction for the synthesis of functionalized saturated N‐heterocycles. Key to the success is to conduct the reactions in a continuous‐flow electrochemical reactor without adding supporting electrolyte or additives. The reactions are characterized by broad tolerance of di‐, tri‐ and tetrasubstituted alkenes.
A continuous‐flow electrochemical aza‐Wacker‐type cyclization reaction that is free of catalyst, oxidant, supporting electrolyte, and additives is presented. The method is scalable and compatible with di‐, tri‐, and tetrasubstituted alkenes.