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3-Methoxypyrazoles from 1,1-dimethoxyethene, few original results

Abstract : From the condensation between 1,1-dimethoxyethene and anhydrides, synthetically useful b,bedimethoxyea,b-unsaturated ketones were prepared. Upon addition of hydrazine, followed by iodination, 4-iodinated 3-methoxypyrazoles were obtained. The occurrence of a side compound also provided insights in the scope of this synthesis. In a second part, 1-(4-chlorophenyl)-3,3-dimethoxyprop- 2-en-1-one was obtained from 1,1-dimethoxyethene and 4-chlorobenzoylchloride. The subsequent addition of hydrazine or phenylhydrazine led to 5-(4-chlorophenyl)-3-methoxy-1H-pyrazole or 1-phenyl- 5-(4-chlorophenyl)-3-methoxypyrazole in unprecedented 64 or 54% overall yield. Unexpectedly, addition of 2-pyridylhydrazine led to the 2-([1,2,4]triazolo[4,3-a]pyridin-3-yl)-1-(4-chlorophenyl) ethanone. This led us to design original conditions, which led to the target 1-(2-pyridyl)-5-(4-chlorophenyl)-3- methoxypyrazole in a 39% overall yield. Additional examples are provided, starting from various carboxychlorides.
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https://hal-pasteur.archives-ouvertes.fr/pasteur-00680094
Contributor : Yves Janin <>
Submitted on : Saturday, March 17, 2012 - 4:13:13 PM
Last modification on : Monday, May 25, 2020 - 11:28:02 PM

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Elise Salanouve, Sandrine Guillou, Marine Bizouarne, Frédéric Bonhomme, Yves L. Janin. 3-Methoxypyrazoles from 1,1-dimethoxyethene, few original results. Tetrahedron, Elsevier, 2012, 68, pp.3165. ⟨10.1016/j.tet.2012.02.057⟩. ⟨pasteur-00680094⟩

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