Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Patent
1996-02-15
1996-10-29
Hamsuer, Robert W.
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C07D23112
Patent
active
055697690
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for preparing pyrazole and its derivatives of the formula I ##STR3## where R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are each hydrogen, halogen, nitro, carboxyl, sulfonyl or C-organic radicals, from alpha,beta-unsaturated carbonyl compounds of the formula II ##STR4## and hydrazine or hydrazine derivatives of the formula III
EP-A 402 722 discloses the preparation of pyrazole and its derivatives from alpha,beta-unsaturated carbonyl compounds and hydrazine or hydrazine derivatives. In the process described therein, either pyrazoline or a carbonyl compound and a hydrazine derivative is reacted in a mixture of sulfuric acid and iodine or a compound which liberates iodine or hydrogen iodide in situ to give the required pyrazole. The yields in the described examples average 78% based on the hydrazine derivative employed.
It is an object of the present invention to prepare pyrazole and its derivatives in a simple manner with improved yields and in higher purity.
We have found that this object is achieved by a process for preparing pyrazole and its derivatives of the formula I ##STR5## where R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are each hydrogen, halogen, nitro, carboxyl, sulfonyl or C-organic radicals, from alpha,beta-unsaturated carbonyl compounds of the formula II ##STR6## and hydrazine or hydrazine derivatives of the formula III carbonyl compound of the formula II is reacted with hydrazine or a hydrazine derivative of the formula III, and the resulting reaction mixture is reacted in another step with a mixture of sulfuric acid and iodine or a compound which liberates iodine or hydrogen iodide.
In this process, initially an alpha,beta-unsaturated carbonyl compound II is mixed with hydrazine or a hydrazine derivative III while maintaining the temperature in the reaction medium during the admixture from to 100.degree. C., preferably 10.degree. C. to 70.degree. C., in particular 20.degree. C. to 50.degree. C. Since the reaction of alpha,beta-unsaturated carbonyl compounds II with hydrazine or a hydrazine derivative III is exothermic, it may be necessary to cool the reaction mixture during the admixture. For the mixing it is immaterial which of the reactants is introduced first or whether the starting materials are introduced into the reaction volume simultaneously but separately. Mixing is completed normally by stirring at the mixing temperature for from 10 minutes to 60 minutes after the addition is complete.
Findings to date indicate that longer stirring times have a negligible effect on the completion of the reaction.
The starting materials are generally reacted together in approximately the stoichiometric amounts, the ratio of carbonyl compound II to hydrazine derivative III normally being from 1:0.65 to 1:1.25 mol/mol. A different ratio of the reactants has a negligible effect on the progress of the reaction and is not worthwhile for economic reasons.
Hydrazine or the hydrazine derivative III can be used either in the form of the hydrates or of the free bases or also in the form of corresponding hydrazonium salts for the present process. Use of salts which are insoluble in the reaction medium may lead to losses of yield owing to inadequate mixing. The hydrates or the free bases of the hydrazine derivatives III are preferably used.
The process is based on the principle of initially forming, by reaction of hydrazines with .alpha.,.beta.-unsaturated carbonyl compounds, the corresponding pyrazolines and secondary products. Workup by distillation after removal of the water of reaction provides only moderate yields because the pyrazolines are accompanied by the byproducts which are formed by addition of the pyrazolines onto the initial carbonyl compounds and which in turn may form hydrazones and azines with the hyrazines.
The resulting reaction mixture is subsequently, without further workup, reacted with a mixture of sulfuric acid and iodine or a compound which liberates iodine or hydrogen iodide. The procedure for this is normally as stated in EP-A 402 722, ie. a mixture of
REFERENCES:
patent: 4996327 (1991-02-01), Merkle et al.
patent: 5128480 (1992-07-01), Merkle et al.
Advances in Heterocyclic Chemistry, Katritzky, vol. 6, 1966.
Pyrazoles, Pyrazolines, Pyrazolidines, Idazoles and Condensed Rings, Behr et al., The Chemistry of Heterocyuclic Compounds, 1967.
Fretschner Erich
Merkle Hans R.
BASF - Aktiengesellschaft
Hamsuer Robert W.
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