Base-Mediated Reaction of Hydrazones and Nitroolefins with a Reversed Regioselectivity:  A Novel Synthesis of 1,3,4-Trisubstituted Pyrazoles

A regioselective synthesis of 1,3,4-tri- or 1,3,4,5-tetrasubstituted pyrazoles by the reaction of hydrazones with nitroolefins is described. Mediated with strong bases such as t-BuOK, the reaction exhibits a reversed, exclusive 1,3,4-regioselectivity. Subsequent quenching with strong acids such as T...

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Bibliographic Details
Published inOrganic letters Vol. 10; no. 6; pp. 1307 - 1310
Main Authors Deng, Xiaohu, Mani, Neelakandha S
Format Journal Article
LanguageEnglish
Published United States American Chemical Society 20.03.2008
Subjects
Alkenes - chemistry
Hydrazones - chemistry
Nitrogen Compounds - chemistry
Pyrazoles - chemical synthesis
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Summary:A regioselective synthesis of 1,3,4-tri- or 1,3,4,5-tetrasubstituted pyrazoles by the reaction of hydrazones with nitroolefins is described. Mediated with strong bases such as t-BuOK, the reaction exhibits a reversed, exclusive 1,3,4-regioselectivity. Subsequent quenching with strong acids such as TFA is essential to achieve good yields. A plausible stepwise cycloaddition reaction mechanism is proposed.
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ISSN:1523-7060
1523-7052
DOI:10.1021/ol800200j