Synthesis of 1-aryl-5-arylazo-3-phenylsulfonylpyrazol-4-ols from 1-bromo-3-phenylsulfonyl-2-propanone

Treatment of 1-chloro-3-phenylsulfonyl-2-propanone (2) with arenediazonium chlorides gave 1 -arylhydrazono-3-chloro-1-phenylsulfonyl-2-propanones 4, which were cyclized in the presence of sodium acetate to 1-aryl-3-phenylsulfonylpyrazol-4-ols 5B. Further treatment of 5B with arenediazonium chlorides yielded 1-aryl-5-arylazo-3-phenylsulfonylpyrazol-4-ols