Issue 2, 2004
From the journal:

Green Chemistry

Solventless syntheses of pyrazole derivatives†

Zhong-Xia Wang*a  and  Hua-Li Qina  

* Corresponding authors

a Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026, P. R. China
E-mail: zxwang@ustc.edu.cn
Fax: 86 551 3631760
Tel: 86 551 3603043

Abstract

Solventless condensation of a diketone and a hydrazine in the presence of a catalytic amount of sulfuric acid at room temperature afforded pyrazole derivatives 3a–3i and 4g–4i in high yields. The condensation of 2,4-pentanedione and hydrazides gave similar results, while the reaction between 1-phenylbutane-1,3-dione and hydrazides under the same conditions afforded 4,5-dihydro-5-hydroxypyrazole derivatives 6a and 6b, which can be transformed to 4i (for 6b) or a mixture of 1-acylpyrazole and 3i (4i) (for 6a) by thermolysis in the presence of a catalytic amount of sulfuric acid. Similar reaction of ethyl acetoacetate with phenylhydrazine or hydrazine formed 2-pyrazolin-5-one 8 and 3-pyrazolin-5-one 9, respectively. Reactions of 2,4-dinitrophenylhydrazine with 2,4-pentanedione and ethyl acetoacetate yielded hydrazones 10 and 11, respectively.

Graphical abstract: Solventless syntheses of pyrazole derivatives

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Article information

DOI
https://doi.org/10.1039/B312833D
Article type
Paper
Submitted
14 Oct 2003
Accepted
21 Nov 2003
First published
08 Jan 2004

Green Chem., 2004,6, 90-92

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Solventless syntheses of pyrazole derivatives

Z. Wang and H. Qin, Green Chem., 2004, 6, 90 DOI: 10.1039/B312833D

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