A rapid, convenient conversion of 1,2‐dimethylpyrazolium salts (1) to 1‐methylpyrazoles (2) is accomplished in piperidine or 3‐methylpiperidine at temperatures ≥ 106°. This demethylation represents a particularly useful procedure for the synthesis of 3‐ and 5‐substituted aminopyrazoles, which are not readily obtainable by other methods. The 50:50 mixture of piperidinopyrazole isomers 2b can be obtained directly by treating 3‐chloro‐1,2‐dimethyl‐5‐phenylpyrazolium iodide (3b) with piperidine in ethanol at 106°.

Die Demethylierung der Pyrazolium‐Salze (I) in Piperidin oder 3‐Methylpiperidin bei 106°C führt zu den isomeren Pyrazolen (II) bzw. (III), deren Gesamtausbeuten bestimmt und deren Anteile in Relation zu den Substituenten diskutiert werden.