Method for the production of purified 1,3-substituted imidazolium salts

A process for preparing purified 1,3-substituted imidazolium salts of the formula (I)

• where
• the radicals R1, R2, R3 and R4 are each, independently of one another, a carbon-comprising organic, saturated or unsaturated, acyclic or cyclic, aliphatic, aromatic or araliphatic radical which has from 1 to 30 carbon atoms and may comprise one or more heteroatoms and/or be substituted by one or more functional groups or halogens, where adjacent radicals R1 and R2, R2 and R3 or R3 and R4 may also be joined to one another and the radicals R2 and R3 may each also be, independently of one another, hydrogen, halogen or a functional group;
• and
• Aa− is the partly or fully deprotonated anion of an inorganic or organic protic acid HaA (III), where a is a positive integer and indicates the charge on the anion,
• which comprises reacting a 1,3-substituted imidazolium salt of the formula (II),
• where the radicals R1, R2, R3 and R4 are as defined above and
• the anion Yy− is the partly or fully deprotonated anion of an inorganic or organic protic acid
• HyY (IV),
• where y is a positive integer and indicates the charge on the anion,
• with a strong base at from 20 to 250° C. while distilling off the 1,3-substituted imidazol-2-ylidene formed, wherein the 1,3-substituted imidazol-2-ylidene which has been distilled off is brought into contact in the gaseous state with the protic acid
• HaA (III)
• and/or the 1,3-substituted imidazol-2-ylidene which has been distilled off is passed in the gaseous or condensed state into a receiver comprising the protic acid HaA (III).