CS233226B1 - The production of 4,5-dichloro-1-phenyl-8-oxo-1 H -pyridazine - Google Patents

Abstract

The invention relates to the production of 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine by the reaction of chlorochloric acid and phenylhydrazine in a dilute hydrochloric acid environment, dicontinuous or continuous* epoeobom in a flow reactor, whereby the inert solution formed after isolation of the 4,5-dichloro-1-phenyl- -6-oxo-1H-pyrldazylne is sometimes used for its production. The mentioned compound is normally used as an anti-product in the production of the herbal preparation Burex.

Description

The present invention relates to a process for the preparation of 4,5-dihydro-1-phenyl-6-oxo-1H-pyridazine.

4,5-Chloro-1-phenyl-6-oxo-1H-pyridazine is an intermediate product in the manufacture of a herbicidal preparation (Burex, Pyramine).

Several methods for the preparation of 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine are known to date. According to DAS 1 086 278, the preparation is carried out by reacting mucochloric acid and phenylhydrazine in an organic solvent medium. MS. AO 205 592 describes the reaction of mucochloric acid with phenylhydrazylic acid in a mixture of an organic non-polar solvent and water. According to US Pat.

628 181, the reaction of mucochloric acid and phenylhydrazine hydrochloride in water in the presence of sodium carbonate is isolated and the resulting phenylhydrazone mucochloric acid product is isolated and boiled in glacial acetic acid to give 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine .

Other known processes for the preparation of 4,5-dichloro-1-phenyl-6-oxo-1 H -pyridazine involve the reaction of a compound of formula I. mucochloric acid and phenylhydrazine in a dilute mineral acid medium (Brit. Pat. No. 881 616; DOS 1 545 595; No. AO 220 299). A common feature of the prior art is that in the production of 4,5-dichloro-1-phenyl-6-oxo-1 H -pyridazine and after isolation of the technical product, liquid environmental wastes remain in which part of the produced 4,5-dichloro-2-ol is dissolved. 1-phenyl-6-oxo-1 H-pyridazine.

A process for the preparation of 4,5-dichloro-1-phenyl-6-oxo-1 H -pyridazine by reacting mucochloric acid and phenylhydrazine in dilute hydrochloric acid continuously or in a batchwise manner according to the invention has been found.

SUMMARY OF THE INVENTION The mother liquor obtained after isolation of the resulting 4,5-dichloro-1-phenyl-6-oxo-1H-pyrldazine is carefully used for its preparation.

The advantage of the new process for the production of 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine lies in its almost waste-free production process, which is of great importance in environmental protection, in particular that unreacted phenylhydrezine as a particularly dangerous poison is virtually absent. to waste vdd. It should be further emphasized that, in the preparation of 4,5-dichloro-1-phenyl-6-oxo-1H-pyrldazine according to the invention, soluble 4,5-dichloro-1-phenyl-6-oxo-1H- pyridazine is used cautiously in the reaction, which is reflected in lower losses due to its solubility. '

The following examples illustrate but do not limit the invention.

EXAMPLE

8.1 kg of mucochloric acid, 125 kg of 1.82% hydrochloric acid and 99.2 kg of a 7% aqueous phenylhydrazine hydrochloride solution were charged to the reaction vessel. The reaction mixture is kept under stirring at 95 ° C for 1 hour. Technical product 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine was isolated by filtration. After washing and drying, 10.95 kg of 99% 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine was obtained, which corresponds to a 95% yield.

Example 2

The mother liquor from the preparation of 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine described in Example 1 weighing 218.6 kg was again charged to the boiler, 5.2 kg of phenylhydrazine and 8.1 kg of acid were added. mucochloric. The reaction mixture was kept under stirring at 95-100 ° C for 1 hour. After cooling the reaction mixture, the solid product was isolated by filtration. 11.3 kg of a 99.1% technical product of 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine, corresponding to a 96.8% yield, were obtained.

Example 3

After 30-fold of the procedure described in Example 2, 11.2 kg of a 99.3% technical product 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine were obtained.

Example 4

13.3 kg of a 6% aqueous solution of mucochloric acid containing 0.23 kg of free hydrogen chloride at a temperature of 60 ° C and 9.9 kg of 7% - was charged to the flow reactor consisting of three boilers connected to each other in a cascade and equipped with a stirrer. % of an aqueous solution of phenylhydrazine hydrochloride. The reaction mixture was held in the reactor at 95 ° C and held for 1 h. The technical product 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine was isolated by filtration. 1.03 kg of a product with a purity of 99% was obtained in 1 hour.

The mother liquor of 22.1 kg was distributed as follows: 12.5 kg after addition with 2.6 g of 31% hydrochloric acid was used to prepare a 6% solution of mucochloric acid and 9.4 kg was used after addition with 12 g of 31% hydrochloric acid for the preparation of 7% phenylhydrazine hydrochloride solution. The procedure described was 360 h.

After 1 h, 1.05 kg of technical 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine was obtained with a purity of 99.4%.

Claims (1)

EXAMPLE 3 11.3 kg of 99.3% non-technical product of 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine were obtained after repeating the procedure described in Example 2 for 30 times. EXAMPLE 4 13.3 kg of a 6% by weight aqueous solution of mesochloric acid containing 0.23 kg of free hydrogen chloride at 60 ° C and 9.9 kg of 7% were metered into a flow reactor consisting of three boilers connected to each other by a stirrer. phenylhydrazine hydrochloride solution. The reaction mixture was kept in the reactor at 95 ° C for 1 h. The product 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine was isolated by filtration. After 1 h, 1.03 kg of 99% pure product was obtained. The 22.1 kg mother liquor was divided as follows: 12.5 kg after addition with 2.6 g of 31% hydrochloric acid was used to prepare a 6% solution of mucochloric acid and 9.4 kg was used after the addition of s, 2 g 31 % hydrochloric acid to prepare a 7% solution of phenylhydrazine hydrochloride. The procedure was 360 h. After 1 h, 1.05 kg of technical 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine was obtained with a purity of 99.4%. SUMMARY OF THE INVENTION The preparation of 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine by reaction of mucochloric acid and phenylhydrazine in dilute hydrochloric acid is effected continually in a flow reactor characterized in that the mother liquor obtained by isolating the resulting 4 5-Dichloro-1-phenyl-6-oxo-1H-pyridazine is used cautiously to manufacture.