Nitration of 3-methyl-1,5-diphenylpyrazole and related compounds

Abstract

Addition of nitric acid (1 mole) to 3-methyl-1,5-diphenylpyrazole (I) in sulphuric acid at 0°, gives the 5-p-nitroderivative (III), which, with excess of nitric acid is converted into the 1,5-di-p-nitro-derivative (VI). Nitrating mixture at 100° introduces a third nitro-group into the 4-position of the pyrazole nucleus. Acetyl nitrate converts (I) into the 4-nitro-compound (X) which, on further stepwise nitration with nitrating mixture, gives first 3-methyl-4-nitro-5-m-nitrophenyl-1-phenylpyrazole (XV) and then 3-methyl-4-nitro-5-m-nitrophenyl-1-p-nitrophenyl-pyrazole (XVII). Various other mono- and di-nitro-compounds have been prepared, and their further nitration has been investigated. Nitration of 4-bromo-3-methyl-1,5-diphenylpyrazole (II) takes a similar course, and the products are identical with those from the bromination of the mono- and di-nitro-compounds from (I). Replacement of bromine by a nitro-group occurred during the nitration of 4-bromo-3-methyl-1,5-di-p-nitrophenylpyrazole (VI) at 100°. Structures were established by chemical methods, supported, where desirable, by n.m.r. spectroscopy.