Reactions of 1-phenylpyrazol-4-ylmagnesium bromide. Part II.

Abstract

1-Phenylpyrazol-4-ylmagnesium bromide reacts with bromide and iodine to give the corresponding 4-halogeno-pyrazole, and with iodine chloride and iodine bromide to give 4-iodo-1-phenylpyrazole, similar yields of which are obtained by the direct iodination of 1-phenylpyrazole. The reaction of the Grignard reagent with various aldehydes has been examined. The Grignard reagent reacts with certain ethyl esters to yield pyrazolylmethanes, and these have been oxidised to the corresponding carbinols. 1,1′-Diphenyl-4,4′-bipyrazolyl, isolated in the Grignard preparation, has been obtained in high yields by prolonged heating of the Grignard reagent. Though 4-iodo-1-phenylpyrazole and 1-(pbromophenyl)pyrazole from Grignard reagents, 4-chloro-1-phenylpyrazole does not.