Preparation and properties of some pyrazolyl ketones

Abstract

Friedel–Crafts acylation reactions of some N-methyl and N-phenylpyrazoles have been investigated and some phenyl pyrazolyl ketones and dipyrazolyl ketones have been prepared. Substitution occurred at the 4-position in the pyrazole nucleus, an exception being the reaction of 1-phenylpyrazole with carbon tetrachloride under Friedel–Crafts conditions. The 1 : 1 aluminium chloride–1-phenylpyrazole complex has been isolated and brominated in neutral solution, and 1-phenylpyrazole has been brominated in strongly acidic solution. Some pyrazole ketones have been converted to esters by the Baeyer–Villiger oxidation with peracetic acid, and migration aptitude has been correlated with the electron-releasing properties of some substituted pyrazole nuclei. The infrared absorption spectra of some pyrazoles have been examined.