Metal-free electrochemical oxidative intramolecular cyclization of N-propargylbenzamides: facile access to oxazole ketals

Here, an unprecedented and sustainable electrochemically driven oxidative 5-exo-dig radical cyclization of N-propargylbenzamides with alcohols is described, which provides a straightforward method to quickly deliver structurally diverse oxazole ketals in moderate to good yields. Achieved under mild conditions in an operationally simple undivided cell without the use of any external transition-metal catalysts, chemical oxidants, and acids required for ketalization, this protocol is scalable and features broad substrate scope and functional group compatibility. Mechanistic studies prove that there is no ketalization process, rather a nucleophilic substitution process is involved.

Automated summary

Here, a novel and sustainable electrochemically driven oxidative 5-exo-dig radical cyclization of N-propargylbenzamides with alcohols is described, providing a convenient method for the synthesis of structurally diverse oxazole ketals in moderate to good yields. This protocol is achieved under mild conditions in an undivided cell without the need for external transition-metal catalysts, chemical oxidants, and ketalization acids, and exhibits scalability, broad substrate scope, and excellent functional group compatibility. Mechanistic studies reveal that the reaction proceeds via a nucleophilic substitution process rather than ketalization.