CS240381B1 - Method of n-aryl-n,n'-dimethylurea preparation - Google Patents

Abstract

Process for preparing N-aryl-N-, N dimethyl-dimethylurea, which is used as biologically active in the manufacture of herbicidal compositions especially for cereals. N-aryl-N, N-dimethylurea is prepared by reaction of dimethylamine with an organic isocyanate solution inert (solvent at temperature -15 to 150 ° C and excess dimethylamine 0.05 to 50% of theory. SUMMARY OF THE INVENTION the reaction is carried out under pressure 0.1 to 0.6 MPa. As aryls, 3- -chloro-4-methylphenyl, 3-chloro-47-methoxyphenyl, 4-isopropylphenyl, 3,4-dichlorophenyl and 3- -nitro-4: methylphenyl. Substituents on phenyl are generalized as follows: in position 3 hydrogen, halogen, n-alkyl C 1 -C 6, alkoxy C 1-6 alkyl; to Cs, NO2 and in position 4 the same and moreover secondary alkyl C 1 to C 18.

Description

Process for the preparation of N-aryl-N ', N'-dimethylurea, which is used as a biologically active substance in the production of herbicidal compositions, in particular for cereals. N-aryl-N ', N'-dimethylurea is prepared by reacting dimethylamine with a solution of aryl isocyanate in an organic inert (solvent at -15 to 150 ° C and an excess of dimethylamine of 0.05 to 50% of theory). reaction is carried out under pressure of 0.1 to 0.6 MPa. the aryl groups include 3-chloro-4-methylphenyl, 3-chloro-47methoxyfenyl, 4-isopropylphenyl, 3,4-dichlorophenyl and _3-nitro-4: methyl phenyl. substituents for phenyl, they are collectively generalized as follows: at the 3-position hydrogen, halogen, n-alkyl C 1 -C 6, alkoxy C 1 -C 6, NO 2, and at the 4-position the same and in addition secondary C 1 -C 6 alkyl.

The invention relates to a process for the preparation of N-aryl-N, N-dimethylurea derivatives of the general formula I

in which

R ¹ represents hydrogen, halogen, n-alkyl C 1 -C 5, secondary alkyl C 5 -C 8, alkoxy C 1 -C 5 or -NO 2 and '

R ² denotes hydrogen, halogen, n-alkyl C 1 -C 5, alkoxy C 1 -C 5 or - NCb by reacting dimethylamine with a solution of aryl isocyanate in general;

in which

R ¹ and R ² are as defined above in an inert organic solvent.

Said N-aryl-N, N'-dimethylurea derivatives are used alone or in combination with other substances as biologically active substances in the production of herbicidal compositions especially for cereals.

Industrial processes for the preparation of N-aryl-N ‘, N‘ → dimethylurea derivatives are mostly based on the reaction of dimethylamine with an arylisocyanate in an organic solvent such as benzene, toluene, chlorobenzene, anisole, dioxane, acetonitrile and the like.

One variant of this process is that an aqueous dimethylamine solution is reacted with a solution of an aryl isocyanate in a praggic solvent. However, the presence of water has a negative effect on the increase in the content of by-products, in particular symmetrical dlarylureas, which arise both during the reaction itself and during the product drying stage, since water reduces the thermal stability of N-aryl-N‘, N‘-dimethylurea. In another variation of this process, a solution of dimethylamine in an organic solvent is used for the reaction. The yield of this process varies from 60 to 95% of theory depending on the concentration of the reacting components and the type of solvent used. The quality of the product depends in particular on the water content of the solvent used, the rate of feed of the components, the molar excess of dimethylamine and the temperature at which the addition of dimethylamine to the aryl isocyanate is carried out. For example, with very rapid dosing (about 0.5 hours) of an arylisocyanate solution to the present solution of dimethylamine in chlorobenzene, products having a symmetrical diaryl urea content of about 10-15% were obtained. The products prepared at a temperature of 40-45 ° C or using an ecimolar amount of dimethylamine and aryl isocyanate contained about 5% symmetrical urea. Optimal reactions are: temperature 0 to 15 ° C, dimethylamine to arylisocyanate molar ratio higher than 1.1: 1. When dispensing 100% dimethylamine directly into the arylisocyanate solution, to prevent dimethylamine exhalation, gaseous or liquid dimethylamine must be brought below the level of the present arylisocyanate solution. However, this is associated with frequent clogging of the lance and the need for mechanical cleaning.

These disadvantages are overcome by the process for preparing N-aryl _? N ', N'-dimethylurea by reacting dimethylamine with a solution of aryl isocyanates in an organic inert solvent, at a temperature of -15 to 150 ° C and an excess of dimethylamine of 0.05 to 50% of the theoretical amount of the present invention. It is carried out in a closed system at a pressure of 0.1 to 0.6 MPa. The gaseous or liquid dimethylamine is fed to the present aryl isocyanate solution in a closed reactor or a solution of both the aryl isocyanate and dimethylamine is fed into the closed reactor.

According to the process of the present invention, products of very high purity can be prepared with yields above 90% of theory and low consumption of dimethylamine (100 to 105% of theory). or in the form of artificially prepared solutions in an inert organic solvent. The dimethylamine feed tube may preferably be placed above the level of the reaction mixture.

To further elucidate the nature of the invention, the following examples are provided:

EXAMPLE 1 Preparation of N- (3-chloro-4-methylphenyl) -N -N, N‘-dimethylurea

2000 g of a chlorobenzene solution of 3-chloro-4-tolylisocyanate containing 300 g of the active substance were introduced into the stirred autoclave and after its closure 82.3 g of liquid were metered in at 30 DEG-45 DEG C. within 3 hours. dimethylamine at a pressure of 0.11 to 0.14 MPa. After the addition of dimethylamine, the contents of the autoclave were heated to 100 ° C and then cooled to 0 ° C over 4 hours. The crystalline product was isolated and dried after washing with 200 g of chlorobenzene. 355.7 g of N- (3-chloro-4-methylphenyl) -N‘, N‘-dimethylurea were obtained, containing

99.5% active ingredient, i.e. a yield of 93% of theory ^1. The mother liquors, after distilling off about 80% chlorobenzene and cooling to 0 ° C, yielded 9.0 g of a second crop of product.

6,

K k k 1 and d 2

Preparation of N- (3-chloro-4-methoxyphenyl) -N -N, N‘-dimethylurea,

2,000 g of a toluene solution of 3-chloro-4-methoxyphenyl isocyanate containing 200 g of the active substance were introduced into the autoclave and after its closure 51 g of dimethylamine gas were metered in at a pressure of 0.14 to 0.20 MPa within 2 hours. and temperature ranging from 60 to 90 ^° C. After stirring for one hour, the reaction mixture was cooled to 0 ° C. The crystalline product was isolated and washed with 100 g of toluene. After drying, 235 g of product with a content of 99.7 percent of active substance were obtained, i.e. in a yield of 94% of theory. The mother liquors, after distilling about 80% of toluene and cooling to 0 ° C, yielded 5.1 g of a second crop of 99.2 percent.

Example 1 a d 3

Preparation of N- (4-isopropylphenyl) -N-N, N-dimethylthio-urea

2000 g of chlorobenzene solution of 4-isopropylphenyl isocyanate containing 448 g of active substance and 150 g of dimethylamine gas were metered into the closed autoclave simultaneously at a temperature of 135 [deg.] C. and a pressure of 0.35 to 0.50 MPa over 40 minutes. Thereafter, the reaction mixture was cooled gradually over a period of 6 hours. Low: 14 ° C. The further procedure was as in Example 1. 552 g of a product with a content of 99.7 O / o of active substance were obtained, i.e. in yield.

95.99% of theory.

Example 4

Preparation of N- (3,4-dichlorophenyl) -N-, N‘-dimethylurea

Into the autoclave, 2000 g of a chlorobenzene-3,4-dichlorophenylisocyanate solution containing 211 g of active substance were initially introduced. After closing the autoclave was charged over 0.5 hours at a temperature from 0 to 25 ^P C and a pressure of 0.11 to 0.15 MPa, a submitted solution of 3,4-dichlorophenyl isocyanate 52 g of gaseous dimethylamine. The reaction mixture was further stirred for 1 hour at 25 ^° C and, after cooling to 0 ° C, the product was isolated. -231 g of dry product were obtained with a content of 99.7% of active substance, i.e. in a yield of 92.9% of theory.

Example 5

Preparation of N- (3-nitro-4-methylphenyl) -N N, N‘-dimethylurea

2000 g of a solution of 3-nitro-4-phenylphenyl isocyanate containing 300 g of active substance were introduced into the autoclave. 102 g of dimethylamine gas were metered in after the autoclave was closed for 4 hours at a temperature of 20 to 40 [ ^deg.] C. and a pressure of 0.1 to 0.2 MPa. The next procedure was as in Example 1. 340 g of a product with a content of 99.1% of the active substance, i.e. a yield of 99.1%, were obtained. in 89.6% of theory.

Claims (1)

SUBJECT VYNALEZU; A process for the preparation of an N-aryl-N ‘, N dimethyl-dimethylurea of the formula I NHCON ^CH 3, Ul where R ¹ denotes hydrogen, halogen, n-alkyl C 1 -C 8, secondary alkyl C 5 -C 8, alkoxy C 1 -C 5 thereof - NO 5, and ' R ² is hydrogen, halogen, N-alkyl Cl to Cs alkoxy, Cl to Cs or -NO 2 / reacting dimethylamine with a solution of an aryl isocyanate of the formula II ¹ -7 VnCO, second (III) in which R ¹ and R ² have in the organic inert solvent at a temperature of -15 to 150 ° C and an excess of dimethylamine of 0.05 to 50% of theory, characterized in that the reaction is carried out in a closed system at a pressure of 0, 1 to 0.6 MPa.