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5-Iodo-3-Ethoxypyrazoles: An Entry Point to New Chemical Entities.

Sandrine Guillou 1 Yves L. Janin 1, *
* Corresponding author
Abstract : Our program, which has focused on the preparation of new pyrazole derivatives, has led us to report here an original and simplified preparation of ethyl 3-ethoxy-1H-pyrazole-4-carboxylate. This is based on the reaction of hydrazine monohydrochloride and diethyl 2-(ethoxymethylene)malonate. Further transformations of this key compound allowed the preparation of the two possible iodinated isomers, namely, 3-ethoxy-4-iodo- and 3-ethoxy-5-iodo-1H-pyrazole. These compounds have opened the way to a quick access to many original pyrazole series. As an illustration, we report here on the selectivity of N-arylation, by using the Lam and Cham method, the C4- and C5-arylation of some of these 3-ethoxypyrazole derivatives by using the Suzuki-Miyaura reaction, and C5-benzylation reactions by means of the Negishi reaction. This was followed by hydrolysis of the ethoxy group, which led to the corresponding pyrazol-3-one derivatives. As a conclusion of this work, we conducted an investigation into the regiochemistry of the condensation between diethyl 2-(ethoxymethylene)malonate and the hydrochloride salts of methyl, benzyl, or phenyl hydrazine.
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Submitted on : Wednesday, April 21, 2010 - 5:41:37 PM
Last modification on : Monday, May 25, 2020 - 11:28:02 PM

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Sandrine Guillou, Yves L. Janin. 5-Iodo-3-Ethoxypyrazoles: An Entry Point to New Chemical Entities.. Chemistry - A European Journal, Wiley-VCH Verlag, 2010, 16 (15), pp.4669-4677. ⟨10.1002/chem.200903442⟩. ⟨pasteur-00475390⟩

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