The preparation of pyrazole and its derivatives

Details The preparation of pyrazole and its derivatives The preparation of pyrazole and its derivatives

C - Chemistry, Metallurgy

07

D

C07D 231/10 (2006.01) C07D 231/12 (2006.01) C07D 521/00 (2006.01)

Patent

CA 2169380

A process is disclosed for preparing pyrazole and its derivatives having formula (I), in which the residues R1, R2, R3 and R4 stand fot hydrogen, halogen, nitro, carboxyl, sulfonyl or C-organic residues, from alpha,beta-unsaturated carbonyl compounds having formula (II) and from hydrazine or hydrazine derivatives having formula (III). The process is characterised in that an alpha,beta-unsaturated carbonyl compound having formula (II) is at first reacted without additional diluting agents with hydrazine or a hydrazine derivative having formula (III), and the thus obtained reaction mixture is reacted in an additional reaction step with a mixture of sulphuric acid and iodine or a iodine- or hydrogen iodide-releasing compound.

L'invention concerne un procédé de préparation de pyrazole et de ses dérivés de la formule (I) dans laquelle les restes R<1>, R<2>, R<3> et R<4> désignent hydrogène, halogène, nitro, carboxyle, sulfonyle ou des restes organiques de C, provenant de composés carbonyle alpha, bêta insaturés de la formule (II) et hydrazine ou des dérivés d'hydrazine de la formule (III). Ce procédé se caractérise en ce que l'on fait d'abord réagir, sans adjonction de diluant, un composé carbonyle alpha, bêta insaturé de la formule (II) avec l'hydrazine ou un de ses dérivés de la formule (III) et que l'on fait ensuite réagir le mélange de réaction ainsi obtenu dans une autre étape de réaction, avec un mélange d'acide sulfurique et d'iode ou avec un composé libérant de l'iode ou de l'iodure d'hydrogène.

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