Synthesis of Triazolium Inner Salts by Thiocyanation of Aldehyde‐Derived Hydrazones

An ammonium persulfate mediated thiocyanation reaction of aldehyde‐derived hydrazones has been carried out under metal‐free conditions at ambient temperature to afford the corresponding 5‐thioxo‐1,2,4‐triazolium inner salts. A library of triazolium inner salts that contain a wide range of functional groups were synthesized in high yields. The reaction proceeds through a thiocyanation followed by isomerization to give the isothiocyanate and subsequent cyclization steps.