Efficient One-Pot, Two-Component Modular Synthesis of 3,5-Disubstituted Pyrazoles

The pyrazole scaffold is one of the
most prevalent and important
tool in medicinal chemistry. Here, we report a method for preparing
3,5-diarylpyrazoles in good to excellent yield by reacting hydrazones
of aryl aldehydes with substituted acetophenones in ethanol in the
presence of dimethyl sulfoxide/cat. I2/cat. HCl. The reverse
process, reacting hydrazones of substituted acetophenones with aryl
aldehydes under the same conditions, also provides 3,5-diarylpyrazoles
in good to excellent yields. Reaction of hydrazones of aldehydes with
2′-aryloxy ketones in the presence of cat. HCl in ethanol and
the catalyst-free reaction of phenacyl bromides with hydrazones of
aldehydes in ethanol also gave good to excellent yields of 3,5-diarylpyrazoles.