Synthesis of bromodifluoromethyl substituted pyrazoles and isoxazoles

Bromodifluoromethyl substituted β-diketone 3a–3d, prepared from corresponding ketones and ethyl bromodifluoroactate in the presence of sodium methoxide, reacted with aryl hydrazine derivatives affording bromodifluoromethyl substituted pyrazoles in high regioselectivity. The reaction of 3a–3d with hydroxylamine hydrochloride gave dihydroisoxazoles, which afforded bromodifluoromethyl substituted isoxazoles through dehydration by PPA or concentrated sulfuric acid.

Bromodifluoromethyl substituted β-diketones reacted with aryl hydrazine derivatives or hydroxylamine hydrochloride affording corresponding bromodifluoromethyl substituted pyrazoles or dihydroisoxazoles, which proceeded dehydration to give bromodifluoromethyl substituted isoxazoles.Figure optionsDownload as PowerPoint slide