- Reactions of Glyoxals with Hydrazones: A New Route to 4-Hydroxypyrazoles
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N-Substituated hyrazones of aldehydes react with glyoxals under non-aqueous conditions to give N-substituted 4-hydroxypyrazoles; fourteen such products are described.In the presence of water, N-substituted 3-acyl-4-hydroxypyrazoles are produced from 2-oxoaldehyde hydrazones and glyoxals.It is shown that glyoxals combine in a 1:1 ratio with N-monosubstituted hydrazones to give 2-hydrazonoaldehydes as the kinetically controlled products.At room temperature or lower, these hydrazonoaldehydes rearrange to the more stable 2-oxoaldehyde hydrazones and react with glyoxals to give N-substituted 3-acyl-4-hydroxypyrazoles; sixteen such products are described.This synthesis, involving easily accessible starting materials, opens up a new, and for certain derivatives exclusive, route to 4-hydroxypyrazoles.
- Begtrup, Mikael,Nytoft, Hans Peter
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- Alkanoyl chloride phenylhydrazones
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Certain alkanoyl chloride phenylhydrazones have been found to be active against insects and mites, and also active as herbicides. The phenylhydrazone ring can be substituted. Suitable substituent groups are halogen atoms, the nitro group, the trifluoromethyl group, and alkyl groups of from 1 to 6 carbon atoms, inclusive. The compounds are prepared by reacting an alkanoic acid phenylhy-drazide with phosphorus pentachloride to obtain an alkanoyl chloride (dichlorophosphinyl)phenylhydrazone intermediate that is reacted with phenol to produce the desired alkanoyl chloride phenylhydrazone. Certain compounds can be prepared by direct chlorination of an alkanaldehyde phenylhydrazone. Some of the compounds are novel. Methods of use and compositions are described.
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