Abstract Treatment of 4-arylamino-4-thioxo-2-butanones with methylhydrazine in acetic acid gives 5-arylamino-1, 3-dimethylpyrazoles which are readily halogenated in the 4 position. The thermal decomposition of 3-anilino-1, 2, 5-trimethyl-1H-pyrazolium chloride gives 1, 3- dimethyl-5-phenylaminopyrazole and 1, 5-dimethyl-3-phenylaminopyrazole in the approximate ratio of 1: 1.
