Synthesis of Rare 1,2,3-Triazolium-5-olates by Electrooxidative Cyclization of α‑Aminocarbonyl Hydrazones

A new method for the synthesis of rare mesoionic heterocycles, namely, 1,2,3-triazolium-5-olates, via electrochemically induced intramolecular N–N bond formation was realized. The process involves electrooxidative cyclization of the readily available α-aminocarbonyl hydrazones, occurs under mild conditions, and enables the preparation of a diverse series of target mesoionics. Additionally, 1,2,3-triazolium-5-olates demonstrated high thermal stability (up to 275 °C) and feature prominent Stokes shifts (7600–8050 cm–1), which enables their application potential for analytical systems and materials science.