CS205592B1 - Method of preparation of the 2-phenyl-4,5-dichlor-pyridasine-3-on - Google Patents

Description

The present invention provides a process for the preparation of 2-phenyl-4,5-dichloropyridazin-3-one,

Heretofore, methods of preparing 2-phenyl-4,5-dihalo-pyridazin-3-one have been known, for example according to DAS 1,086,238 from mucohoric acid and phenylhydrazine in an organic solvent medium, wherein the water formed in the reaction is continuously removed from the reaction medium as an azeotrope.

Other known methods are based on the reaction of mucohoric acid and phenylhydrazine hydrochloride in an aqueous medium. According to US Pat. no. No. 2,628,181 is carried out by reacting mucohoric acid and phenylhydrazine hydrochloride in water in the presence of sodium carbonate, isolating the resulting phenylhydrazone mucohoric acid product and boiling in glacial acetic acid to give 2-phenyl-4,5-diohoropyridazin-3-one. The violet known production method is carried out by reacting mucohoric acid and phenylhydrazine in dilute hydrochloric acid (Brit. Pat. No. 881 616, Frano. Pat. No. 1 261 605). Continuously carrying out said process in a cascade of multiple boilers is the subject of DOS 1 545 595.

The present invention relates to a process for the continuous production of 2-phenyl-4,5-diohoropyridazin-3-one by the reaction of an aqueous solution of mucohoric acid and phenylhydrazine hydrochloride in an inert non-polar solvent and water. 2. 197 194.

205 592

203 S92

It has now been found that 2-phenyl-4,5-diohoropyridazin-3-one can be prepared under advantageous conditions by reacting an aqueous solution of mucohoric acid and phenylhydrazine with a relative ratio of mucohoric acid and phenylhydrazine of 0.8 to 1.2: 1 under inert conditions. a non-polar solvent selected from the group consisting of aromatic hydrocarbons, halogenated aromatic hydrocarbons, halogenated aliphatic hydrocarbons having from 1 to 3 carbon atoms such as benzene, toluene, xylene, chlorobenzene, chloroform, carbon tetrachloride, dichloroethane and dihydrochloric acid in dichloromethane.

The invention is based on the fact that phenylhydrazine enters the reaction in the form of a solution in an inert, non-polar solvent and, when the reaction is carried out in the presence of hydrochloric acid, the molar ratio of hydrogen to phenylhydrazine is less than 1.

From the advantages of the above mentioned process it is necessary to mention higher reactivity

The short reaction time makes it possible to carry out the reaction as a batch, i. discontinuously as well as continuously, for example in a boiler cascade or in a vertical column, in a snake reactor.

The following examples illustrate but do not limit the scope of the invention.

Example 1

To a solution of 22.3 g (0.206 M) of phenylhydrazine and 275 ml of 92 ° C warm xylene in a flask equipped with a stirrer, thermometer, smooth flask, dosing and discharge port was added an aqueous solution of 80 ° C warm, consisting of 33.6 g. (0.2 M) of mucohoric acid and 400 ml of water. The reaction mixture was maintained at reflux temperature for 10 ml with stirring. After this time and the stirrer was stopped, the reaction mixture was stratified and the aqueous phase was discharged through a drain. After distilling off the xylene, 46.6 g of the 2-phenyl-4,5'-dihalo-pyridazin-3-one theohalo-product of 96% purity, ie. 92.8% of theory.

Example 2

To a mixture of 33.6 g (0.2 L) of mucohoric acid, 135 mL of water and 275 mL of xylene at 90-92 ° C was added 85 warm solution of 22.3 g (0.206 M) of phenylhydrazine in 276 g of 0.74% hydrochloric acid (0.056 II). The reaction mixture was maintained at reflux temperature for 10 ml. The procedure was as in Example 1 to obtain 45.7 g of the technical product 2-phenyl-4,5-diohoropyridazin-3-one of 96.2% purity.

Example 3

353 g of an aqueous 9% sodium phenylhydrazine disulfate solution was heated to 80-90 ° C and 64.0 g of 32% hydrochloric acid was added over 1 hour. The reaction mixture was maintained at this temperature for 2 hours with stirring. After the reaction time, the mixture was neutralized with NaOH until the alkali metal reaction. At 50 ° C phenylhydrazine was extracted with 275 ml of xylene. After separation and heating to 88-90 [deg.] C, 33.6 g of mucoic acid in 400 ml of water was added to the 90 [deg.] C warm solution. After 10 ml of reflux the reaction mixture

205,592 was processed as in Example 1.

42.8 g of 2-phenyl-4,5-diohoropyridazin-3-one, pyrogenic, purity 96.1% were obtained.

Example 4

The procedure was as in Example 1 except that 275 ml of chlorobenzene was used instead of xylene. 45 g of 2-phenyl-4,5-dihydropyridazin-3-one obtained a purity of 97.1%, i.e., 90.65% of theory.

Example 5

The procedure was as in Example 3 except that 200 ml of 1,2-dichloroethane was used to extract the phenylhydrazine. To a solution of phenylhydrazine in dichloroethane was added

33.6 g of mucohoric acid in 400 ml of water at 50 ° C. After 10 minutes at reflux, the reaction mixture was worked up as in Example 1.

43 S of 2-phenyl-4,5-diohoropyridazin-3-one with 95% purity was obtained.

Example 6

353 g of an aqueous 9% sodium phenylhydrazine disulfonate solution was heated to 80-90 ° C and 64 g of 32% hydrochloric acid was added over 1 hour. The reaction mixture was maintained at this temperature for 2 hours with stirring. After the reaction time, the mixture was neutralized with ammonia water to pH 7. At 45 ° C and the phenylhydrazine was extracted with 300 ml of toluene. After separation, a warm solution of 33.6 g of mucoic acid in 400 ml of water was added to a 60 ° C warm solution. After 10 minutes at reflux, the reaction mixture was worked up as in Example 1.

42.5 g of 96.5% pure 2-phenyl-4,5-dichloropyridazin-3-one are concentrated.

Claims (1)

OBJECT OF THE INVENTION A process for the preparation of 2-phenyl-4,5-diohoropyridazin-3-one by reacting an aqueous solution of mucohoric acid and phenylhydrazine with a ratio of mucohoric acid to phenylhydrazine of 0.8 to 1.2 t to each other in an inert non-polar solvent of aromatic hydrocarbons halogenated aliphatic hydrocarbons having from 1 to 3 carbon atoms, such as benzene, toluene, xylene, chlorobenzene, chloroform, carbon tetrachloride, diohloroethane, dichloropropane and optionally in the presence of hydrochloric acid, characterized in that the phenylhydrazine is reacted as a solution in an inert nonpolar the solvent and, if the reaction is carried out in the presence of hydrochloric acid, the molar ratio of hydrogen chloride to phenylhydrazine to each other is less than 1.