Direct synthesis of 3-(fluoroalkyl)pyrazoles from polyfluoroalkyl aldehydes

Abstract

3-(Fluoroalkyl)pyrazoles 3 have been synthesized in excellent yields by reaction of various fluoroalkyl aldehydes with NH₂NH₂·HOAc under mild conditions. It appears that the reaction involves the formation of a hydrazone intermediate, followed by elimination of hydrogen halide and intramolecular nucleophilic addition. A practical one-pot synthesis of 3-(fluoroalky1)pyrazoles from polyfluoroalkyl iodides 1 has also been developed.