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Issue 2, 2004
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Solventless syntheses of pyrazole derivatives

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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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Publication details

The article was received on 14 Oct 2003, accepted on 21 Nov 2003 and first published on 08 Jan 2004


Article type: Paper
DOI: 10.1039/B312833D
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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