Verfahren zur Herstellung von 1,2-Dimethyl-3,5-diaryl-pyrazoliummethylsulfaten

摘要

The invention concerns a method of preparing 1,2-dimethyl-3,5-diarylpyrazolium methylsulphates of general formula (I) in which R<1> and R<2>, independently of each other, may be hydrogen, C1-C4 alkyl, C3-C8 cycloalkyl, C1-C4 alkoxy, halogen, nitro C1-C4 haloalkyl, aryl or other substituents which are inert under the conditions of the reaction. The method calls for 1-methyl-3,5-diarylpyrazoles of general formula (II), in which R<1> and R<2> are as defined above, to be reacted at elevated temperatures with a) methanol and SO3, b) methanol and sulphuric acid and/or c) methanol and methylsulphuric acid.