Sequential Three-Component Reactions for the Assembly of Functionalized Pyrazoles
Author(s): Li, Yufeng, Huang, Jiawei, Gu, Jiachao, Huang, Hao, Niu, Changsheng, Ma, Hongfei, College of Chemistry and Molecular Engineering, Nanjing Tech University
Pages: 520-526
Year: 2016 Issue: 3
Journal: Chinese Journal of Organic Chemistry
Keyword: hydrazine; aldehyde; methyl propiolate; pyrazoles; three-component reaction;
Abstract: A sequential three-component reaction for the assembly of functionalized pyrazoles is described. Aldehydes are treated with hydrazines in dichloroethane to generate hydrazones(3), which in situ take place aza-Michael reaction quickly with methyl propiolate(4) catalyzed by Cu Cl to give Michael adducts(5). Subsequent oxidation of 5 with stoichiometric Fe Cl3 provides substituted pyrazoles with high to excellent yields. The intermediates of the synthetic method are not necessary to isolate. Aliphatic hydrazines, aromatic hydrazines as well as aromatic aldehydes are well adaptable to the reaction.
Pages: 520-526
Year: 2016 Issue: 3
Journal: Chinese Journal of Organic Chemistry
Keyword: hydrazine; aldehyde; methyl propiolate; pyrazoles; three-component reaction;
Abstract: A sequential three-component reaction for the assembly of functionalized pyrazoles is described. Aldehydes are treated with hydrazines in dichloroethane to generate hydrazones(3), which in situ take place aza-Michael reaction quickly with methyl propiolate(4) catalyzed by Cu Cl to give Michael adducts(5). Subsequent oxidation of 5 with stoichiometric Fe Cl3 provides substituted pyrazoles with high to excellent yields. The intermediates of the synthetic method are not necessary to isolate. Aliphatic hydrazines, aromatic hydrazines as well as aromatic aldehydes are well adaptable to the reaction.
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