GB793063A - New nitrosopyrazoles and fungicidal compositions containing them - Google Patents

Abstract

The invention comprises 1-cycloalkyl-3 : 5-dimethyl-4-nitrosopyrazoles wherein the cycloalkyl radical is the cyclopentyl, cyclohexyl or cycloheptyl radical. The novel compounds may be prepared by condensing the isonitrosoketone, obtained by nitrosating acetylacetone, with cyclopentylhydrazine, cyclohexylhydrazine or cycloheptylhydrazine. In examples: (1) a solution of isonitrosoketone in water is added dropwise with stirring to an ice-cooled solution of cyclohexylhydrazine hydrochloride to give 1-cyclohexyl - 3 : 5 - dimethyl - 4 - nitrosopyrazole; (2) 1 - cyclopentyl - 3 : 5 - dimethyl - 4 - nitrosopyrazole; and (3) 1-cycloheptyl-3 : 5-dimethyl-4-nitrosopyrazole are prepared in similar manner. The products may be used to prepare fungicidal compositions (see Group VI). Cyclohexylhydrazine is prepared by dissolving cyclohexanone with cooling in a solution of hydrazine hydrate in hydrochloric acid and hydrogenating the solution in the presence of chloroplatinic acid and gum-arabic. The hydrazine hydrate-hydrochloric acid mixture may be replaced by a salt such as hydrazine hydrochloride or hydrazine sulphate. Cyclopentyl hydrazine hydrochloride may be prepared in analogous manner.ALSO:A fungicidal composition contains at least one of the compounds 1-cyclopentyl-, 1-cyclohexyl-, and 1-cycloheptyl-3: 5-dimethyl-4-nitrosopyrazole in association with a diluent. (For preparation see Group IV (b)). The fungicidal compositions may be in the form of dusts, dispersions and emulsions and may contain in addition to the above compounds, one or more substances known to be active as fungicides, bactericides, insecticides, fertilizers or plant-growth regulators. Typical compositions are: (a) wettable powders comprising the active material dispersed up to 50 per cent w./w. in an inert absorbent carrier such as a silicaceous earth together with an ionic or non-ionic wetting and/or dispersing agent such as an alkali metal salt of a long-chain aliphatic sulphate, a partly neutralized sulphuric acid derivative of a petroleum oil or of naturally occurring glycerides or a condensation product of an alkaline oxide with an organic acid; (b) self-emulsifying concentrates comprising the active material in solution in a concentration of up to 80 per cent w./v. in a solvent such as an aromatic hydrocarbon (e.g. xylene), solvent naphtha or a mineral oil together with a wetting and/or dispersing agent; (c) dusts containing the active material dispersed in an inert absorbent carrier diluted with inert carriers such as talc, diatomaceous earths, wood-flours and clays; (d) compositions of the active material formulated in conventional manner for the preparation of smokes, dusts and aerosols. Compositions under (a) and (b) yield, on dilution with water to a concentration of 0.025 to 0.4 per cent w./v. of active material, stable suspensions and emulsions for use in the form of a spray. Examples demonstrate the activity of the new compounds in aqueous suspensions compared to the known fungicides 1 - phenyl - 3:5 - dimethyl - 4 - nitroso pyrazole and N-trichloromethylthiotetrahydrophthalimide. The activities of the test compounds is also determined by incorporating in maltose agar in a range of serial dilutions, inoculating with fungi and incubating the cultures for 5 days at 30 DEG C.