GB632832A - Manufacture of pyrazolones substituted in the 3-position - Google Patents

Abstract

5-Pyrazolones substituted in the 3-position by a residue having more than one carbon atom are manufactured by reaction of a hydrazine (e.g. hydrazine itself, an alkylhydrazine or especially an arylhydrazine, in which the aryl residue may be substituted) with an acylacetic arylide of which the acyl residue contains more than two carbon atoms and in which the -CH2- group of the acylacetic acid residue is unsubstituted. The reaction may be carried out in an alcoholic, aqueous-alcoholic or acetic acid medium. In examples: (1) benzoylacetanilide and hydrazine sulphate are refluxed in aqueous alcohol in the presence of sodium acetate to produce 3-phenyl-5-pyrazolone; the benzoylacetanilide may be replaced by its p-chloro derivative or the hydrazine sulphate by methylhydrazine or by phenylhydrazine, m-nitro, o-, m- or p-chloro, p-methoxy, p-ethoxy or 2 : 5-dichloro derivative or its m- or p-sulphonic or carboxylic acid; (2) 3-nitro-4-methoxybenzoylacetanilide and hydrazine sulphate similarly yield 3-(31-nitro-41-methoxy-phenyl)-5-pyrazolone; the hydrazine sulphate may be replaced by methyl- or phenyl-hydrazine; (3) cinnamoylacetanilide and hydrazine sulphate similarly yield 3-styryl-5-pyrazolone; (4) benzoylacetanilide and phenylhydrazine-p-sulphonic acid are refluxed in aqueous acetic acid to form 1-(p-sulphophenyl)-3-phenyl-5-pyrazolone; the phenylhydrazine-p-sulphonic acid may be replaced by 2-chloro-4-sulphophenylhydrazine. The acylacetanilides may be replaced by analogous compounds in which the anilide residue contains substituents, but without altering the composition of the product obtained. Specifications 20391/47 (as open to inspection under Sect. 91) and 632,341 are referred to.