Some reactions of 1-phenylpyrazol-4-ylmagnesium bromide

Abstract

1-Phenylpyrazole-4-carboxylic acid has been prepared in high yield by the carbonation of 1-phenylpyrazol-4-ylmagnesium bromide. 1,1′-Diphenyl-4,4′-bipyrazolyl has always been obtained as a by-product in the preparation of this Grignard reagent, and the yield has been increased by the action of cobaltous chloride on the Grignard reagent. The Grignard reagent reacts with ketones to form tertiary alcohols and with acid chlorides to form ketones. The preparation of the same ketones from the reaction of 1-phenylpyrazole-4-carbonyl chloride with various Grignard reagents nearly always resulted in lower yields or failure. Only methylmagnesium iodide gave a high yield of ketone.