Electrochemical Synthesis of 3,5-Disubstituted Pyrazoles from Ynone Hydrazones via Diselenide-Catalyzed Cyclization Strategy.

Given the existing limitations of traditional methods for the synthesis of pyrazole derivatives, developing new, mild, and efficient approach toward pyrazole skeletons is necessary. Herein, we report an electrochemically driven diselenide-catalyzed cyclization of 1,3-disubstituted prop-2-yn-1-one hydrazones that realize the rapid synthesis of 3,5-disubstituted pyrazoles under metal-free, oxidant-free, and base-free conditions. The practical utility of this method is underscored by its wide substrate scope, high tolerance toward various functional groups, high efficiency, mild conditions, gram-scale synthesis, and diverse derivatizations. Furthermore, the preliminary mechanistic experiments indicate that this reaction possibly proceeds via a cationic pathway.