1-Phenylpyrazole and nitrophenylpyrazoles have been converted into trinitro-compounds by mixed acids a t loo", and the products orientated by synthesis. Some di-and the tri-nitrophenylpyrazoles give colours in the Janovsky reaction.l* NITRATION of l-phenylpyrazole with mixed acids at 100" gives 1-(2 : 4-dinitrophenyl)-4nitropyrazole ; the course of the reaction is indicated by nitration of l-phenylpyrazole at 12" and 22" which gives the intermediates l-p-nitrophenyl-and 4-nitro-l-p-nitrophenylpyrazole, respectively. Nitration of both these compounds a t 100" gives the trinitrocompound, which is also obtained by other nitrations (see Table ).1-(2 : 4-Dinitrophenyl)-4-nitropyrazole was characterised by its reaction with boiling methanolic sodium methoxide to give 4-nitropyrazole and 2 : 4-dinitroanisole. It was synthesised by condensation between 4-nitropyrazole [from pyrazole,* by nitration with mixed acids at 100" (cf. Buchner and F r i ~c h , ~ and Huttel et aZ.6)] and l-chloro-2 : 4-dinitrobenzene in ethanolic potassium hydroxide. Nitration of l-m-nitrophenyl-and 4-nitro-1-m-nitrophenyl-pyrazole with mixed acids at 100" gives 1 -(3 : 4-dinitrophenyl)-4-nitropyrazole, the orientation of which was established as follows. One nitro-group underwent nucleophilic replacement in ethanolic ammonia at loo", to give an amine which, on deamination, gave 4-nitro-l-~-nitrophenylpyrazole, the presence of a 9-nitro-group in the trinitro-compound being thus established. This trinitro-compound was synthesised as follows : Partial reduction of 4-nitro-l-p-nitrophenylpyrazole with ammonium hydrogen sulphide gave l-~-aminophenyl-4-nitropyrazole (the structure being shown by deamination

Various pyrazoles have been formylated, and these derivatives oxidised to the corresponding acids. Thionyl chloride reacts directly with l-phenylpyrazole to give the dipyrazolyl sulphoxide which has been oxidised to the sulphone. 4-Fomyl-l-phenylpyrazole gives the expected alcohols with Grignard reagents, except that ethylmagnesium halide gave 4-propenyl-1phenylpyrazole and a dimer. The alcohols have been oxidised to the ketones, and some of these reduced to alkyl compounds by the Clemmensen method. Both 4-fomyl-l-phenylpyrazole and 1-phenylpyrazole-4-carboxyIic acid have been reduced by lithium aluminium hydride to 4-hydroxymethyl-lphenylpyrazole. Two bipyrazolyls and one terpyrazole have also been prepared.

The preparation of 1 -phenylpyrazole from epichlorohydrin and phenylhydrazine has been improved, and the method has been extended to include the use of nitrophenylhydrazines. Some 4-substituted derivatives of 1-phenylpyrazole have been prepared, and their properties have been investigated.

No abstract

No abstract

The steric effects of substituents and the position of protonation in strongly acidic media are discussed in terms of the changes observed in ultraviolet and n m r . absorption. A new series of 1 -pentafluorophenylpyrazoles has been synthesrsed, and their spectra are compared with those of the parent pyrazoles. Twenty-five commonly occurring bands in the infrared spectra of 1 -phenylpyrazoles are tabulated and assignments have been made.FURTHER to recent ultraviolet ( U . V . ) ~~ and nuclear magnetic resonance (n.m.r,)5-7 spectroscopic studies, we report an investigation of seventy 1-phenylpyrazole (I) derivatives by u.v., n.m.r., and infrared (ix.) methods.

No abstract

No abstract