| 摘要 |
3,5-Diphenylpyrazole, 3,5-diphenyl-4-alkylpyrazoles or 3,5-diphenyl-4-alkoxypyrazoles are prepared from the corresponding pyrazolines by catalytic dehydrogenation in an inert organic solvent. Platinum or palladium, both of which can also be supported by various substances, can be used as catalysts. The pyrazolines used as starting material can be obtained by reacting a methyl ketone, such as acetophenone or its derivatives, with a suitable aldehyde, such as benzaldehyde, in the presence of a base, to give a 1,3-disubstituted alpha , beta -unsaturated ketone, such as chalcone or its substitution products, acidification of the resulting reaction mixture and treatment of the acidified reaction mixture with hydrazine. The compounds prepared according to the invention can be used as starting substances for the preparation of corresponding 3,5-disubstituted 1,2-dialkylpyrazolium salts, such as 1,2-dimethyl-3,5-diphenylpyrazolium methyl sulphate which, in turn, can be used as herbicides. |
