CS243579B1 - Continuous method of n-aryl-n'-dimethylureas' derivatives preparation - Google Patents

Abstract

Process for preparing N-aryl-N, N-dimethylurea derivatives general formula CHj ch5 where R 1 is H, F, Cl, C 1 -C 8 alkyl, secondary C 3 -C 8 alkyl, -CN, C 1 -C 5 alkoxy and R 2 is H, F, Cl, C 1 -C 8 alkyl, secondary C 3 -C 8 alkyl, -CN, -CF 3, C 1 -C 6 alkoxy Cs by reaction of dimethylamine with an aryl isocyanate in an organic solvent environment by continuously carrying out the reaction in a column type reactor at temperature 50 ° C to the boiling point of the reaction mixture at a molar ratio of dimethylamine to aryl isocyanate 0.95 to 1.20: 1.00, preferably however, 0.99 to 1.01: 1.00. Column efficiency reactor is at least 3. theor. palate a the residence time is 0.5 to 30 min.

Description

The present invention relates to a continuous process for the preparation of N-aryl-N ‘, N‘-dimethylurea derivatives of the general formula:

in which '

R1 denotes H, F, Cl, C1-C8 alkyl, C1-C8 secondary alkyl, -CN, C1-C8 alkoxy and

R 2 denotes H, F, Cl, alkyl C 1 -C 5, secondary alkyl C 3 -C 5, -CN, -CF 3, alkoxy C 1 -C 5 by reaction of dimethylamine with aryl isocyanate in an organic inert 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 preparations, especially for cereals.

Among the known processes for the preparation of N-aryl-N ‘, N‘-dimethylurea derivatives, industrial processes are based on the reaction of dimethylamine in a solution of water or an organic solvent or in the form of a 100% substance with an aryl isocyanate in an organic inert solvent.

Usually, it is operated in a hatching manner, ie. by dispensing dimethylamine, e.g. of a solution or solution in an organic solvent to the present solution of arylisocyanate in an organic solvent.

The reaction itself is carried out at normal or elevated temperature using a certain excess of dimethylamine, which must be removed by heating the reaction mixture to a temperature of at least 70-80 ° C. Residues of dimethylamine must also be removed during solvent recovery.

However, prolonged thermal exposure at a higher temperature results in the desired N-aryl-N ', N'-dimethylurea decomposing into the corresponding symmetrical N, N'-diarylurea, thereby reducing the yield of the desired product and consequently increasing waste in processing the liquidation of which is quite demanding.

These drawbacks are attempted to address processes where the continuous production of aryl isocyanates is followed by the continuous preparation of N-aryl-N ', N'-dimethylureas, which is principally carried out in a cascade of boiler reactors at temperatures of 80 to 140 ° C. heating to a higher temperature or stripping with nitrogen. This arrangement partially solves the problem of thermal exposure and hence the degree of symmetric urea formation, which is dependent on the thermal exposure time. In terms of apparatus, this arrangement is quite complicated.

These disadvantages are overcome by the process for the preparation of N-aryl-N ‘, N‘-dimethylurea derivatives by reaction of dimethylamine with aryl isocyanate.

According to the invention, the reaction is carried out continuously in a column type reactor at 50 degrees C up to the boiling point of the reaction mixture. The reaction is carried out by treating dimethylamine with a solution of the aryl isocyanate in an inert organic solvent such as toluene, anisole, acetone, chlorobenzene, xylene.

Dimethylamine is added to the aryl isocyanate in a molar ratio of 0.95 to 1.2: 1.00, preferably 0.99 to 1.01: 1.00. The reaction mixture leaving the digester (bottom of the column) of the column type reactor with a minimum efficiency of 3 theoretical plates and a residence time of 0.5 to 30 minutes is immediately cooled to 40 to 70 ° C depending on the concentration of N-aryl-N 'formed. , N'-dimethylurea. The process of the invention makes use of the fact that the reaction is virtually instantaneous.

The reactor column type may be arranged such that the gaseous or liquid ^one dimethylamine or dimethylamine solution in an organic solvent introduced into the reactor column of the type is irrigated with a solution of an aryl isocyanate in an organic solvent.

The reactor maintains a temperature ensuring the solubility of the resulting N-aryl-N N, N‘-dimethylurea, which is at least 50 ° C. The solution of the reaction product in the organic solvent flows through the aftercooler from the bottom of the column to the crystallizer.

In another arrangement, a column reactor (below the arylisocyanate feed point) is placed in the bottom of the reactor. of the type dispensed liquid or gaseous dimethylamine in the form of 100% substance or a solution thereof in an organic solvent. Unreacted dimethylamine is distilled off by heating the reactor of the reactor to the boiling point of the reaction mixture, and the leaving vapors in the column type reactor are sprinkled with a fresh arylisocyanate solution which is fed to the top of the column type reactor. The most suitable concentration of N-aryl-N ‘, N‘-dimethylurea in the reaction mixture is such that the onset of crystallization of the reaction mixture qd corresponds to a temperature of 40 to 70 ° C. This arrangement makes it possible to work with dilute solutions of the reactants and to ensure the necessary concentration of N-aryl-N ‘, N dimethyl-dimethylurea by distilling off the solvent simultaneously during the actual reaction.

This solution makes it possible to work at optimum concentrations and thus ensure maximum crystallization yield without any treatment of the reaction mixture or mother liquors (2 nd product fraction), since the reaction mixture leaving the column type reactol is subjected to conventional crystallization by successive cooling to temperatures of about 0 ° C. .24 3 5 7 9 is isolated on a conventional equipment suitable for working with an organic solvent. The product obtained is of very high purity and the yields to be recovered are between 90 and 98% depending on the concentration of the product in the reaction mixture.

The advantage of this process is that, due to the short contact time, in minutes, which minimizes thermal exposure, high product quality and high yield are ensured. A further advantage is that when dimethylamine is dosed approximately equimolar to the aryl isocyanate, the need for regenerating excess dimethylamine is eliminated; if dimethylamine is dosed in excess, excess dimethylamine is absorbed in an auxiliary absorption column trickled with an organic solvent (a less preferred alternative). However, the actual reaction and removal of excess dimethylamine takes place in one step in a column type reactor.

The process according to the invention further reduces the investment costs for the construction of the equipment, significantly increases the productivity of the equipment and ensures the stability of the operation of the production, which results in minimizing the influence of the operator.

The construction of a column type reactor, for example packed, trayed and the like, does not require special claims. The continualization of the reaction of dimethylamine with an arylisocyanate should be complemented by the continualization of solvent regeneration by a system of distillation continuous columns.

In order that the invention may be more fully understood, the following examples are provided.

Example 1

Preparation of N- (3-chloro-4-methylphenyl) -N-, N‘-dimethylmorea

Experiment conditions:

concentration of 4-isopropylphenylisocyanate in chlorobenzene dosing of dimethylamine components (liquid - gasification in the reactor immediately) solution of 4-isopropylphenylisocyanate in chlorobenzene distilled chlorobenzene during the reaction time of dosing temperature in the reactor boiler temperature at the top of the column (reactor)

883.3 g of product was obtained

99.5% of the active substance, i.e. in a yield of 98.1% of theory.

Example 3

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

53.8 g was fed to the bottom of the 10-bell-type column type reactor. h ^_1 Dimethylamine gas and simultaneously into the upper part of the reactor columns | tion type was dosed chlorobenzene solution of 3-chloro-4-methyl-phenyl isocyanate of 20% by weight in an amount of 1000 g. h ^- ' ¹ . The boiling point of the reactor was maintained at about 135 ° C during the dosing of both components and was heated to 90-91 ° C during the metering at the top of the column type reactor. The total feed time of both components into the column type reactor was 4 hours and the residence time in the reactor was three minutes. The reaction mixture (a solution of N- (3-chloro-4-methylphenyl) -N ', N'-dimethylurea in chlorobenzene) flowed continuously from the reactor digester to the crystallizer, where the temperature was in the range of 50-57 ° C during the reaction mixture flow. The total feed time of both components to the column type reactor was 4 hours. After cooling the product suspension in chlorocarbenzene to 0 [deg.] C., the product was isolated in a conventional centrifuge and dried in a rotary vacuum oven at 75-85 [deg.] C. and a pressure of 0.0001 MPa for 3 hours. 985.7 grams of product with 99.9% of active substance, i.e. in 97.0% of theory, were obtained.

Example 2

Preparation of N- (4-isopropylphenyl) -N‘, N‘-dimethylurea

The product was prepared analogously to Example 1 continuously in a packed column type reactor (Raschig rings) with 5 theoretical plates efficiency and a residence time of 4 minutes, except that part of the solvent was distilled off during the reaction.

10.0%

27.8 g. H-1

1000 g. Hi

400 g. H-7 for 7 hours

134-135 ° C 90-91 ° C

The product was prepared continuously in a packed column reactor (Canon rings) with an efficiency of 3 theoretical plates, with a residence time of 0.5 min. 100% 3-chloro-4-methoxyphenyl isocyanate and m-xylene solvent were separately charged to the reactor.

.243579

Experimental conditions: dosing of components dimethylamine (gaseous) 3-chloro-4-methoxyphenyl isocyanate m-xylene dosing time temperature in the reactor digester temperature at the top of the column - reactor (total reflux)

1084.8 g of product were obtained with a content of 99.2% of active substance, i.e. in a yield of 96.0% of theory.

Example 4

Preparation of N- (3-trifluoromethylphenyl) -N), N‘-dimethylurea

Prepared continuously in a round-type reactor with 25 teore efficiency.

dosing of dimethylamine components solution of 3-trifluoromethylphenylisocyanate in toluene concentration of 3-trifluoromethylphenylisocyanate solution time of dosing temperature at the bottom of the reactor (column base)

882 g of product were obtained with a content of 99.4% of active substance, i.e. in a yield of 94.2% of theory.

Example 5

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

The preparation was carried out continuously in a column type reactor with a loading of 6 theoretical plates, residence time of the dimethylamine components 3-cyano-4-methylphenylisocyanate gas solution dosing time temperature in the reactor boiler temperature at the top of the reactor column

1,226.0 g of the product with a content were obtained

99.6% of the active substance, i.e. in a yield of 97.4% of theory.

Example 6

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

72.2 g.h-l

300 g. Hi 1200 g. H-i 3 hours

140 [deg.] C

139 DEG C., the residence time was 30 minutes at a temperature lower than the boiling point of the reaction mixture. Dimethylamine gas was fed to the middle of the column type reactor and was sprinkled with a solution of 3-trifluoromethylphenyl isocyanate in toluene which was fed to the top of the reactor. A solution of the product in toluene was taken continuously from the bottom of the column (reactor) to the crystallizer.

90.5 g. Hi 2,500 g. h ^_1 %

to 85 ° C to 95 ° C was 2.5 minutes. Dimethylamine was dosed at about 110% of theory and excess dimethylamine leaving the top of the column was discharged to the bottom of the absorbent column, which was sprinkled with circulating toluene.

Experiment conditions:

concentration of toluene solution of 3-cyano-4-methoxyphenyl isocyanate%

35,6 g. h ~ i

500 g.h-1 8 hours

112 [deg.] C

Mp 109-108 ° C

The preparation was carried out continuously in a column-type reactor with 4 bell plates, with a residence time of 2 minutes. A solution of dimethylamine in anisole was charged to the reactor.

243573

Experiment conditions:

concentration of 3,4-dichlorophenylisocyanate in anisole solution 31.5% dosing of components solution of dimethylaraine in anisole with concentration 31.65% solution of 3,4-dichlorophenylisocyanate in anisole temperature in the reactor boiler temperature at the top of the reactor column time of dosing

1363 g of product were obtained.

146.3 g. h-i

600 g.lr ¹ 155 ° C 120 ° C hours content 99,9% of the active substance, ie in a yield of 86,8 teo

Claims (1)

Continuous preparation of N-aryl-N ', N‘-dimethylurea derivatives of the general formula wherein R 1 is H, F, Cl, C 1 -C 5 alkyl, C 3 -C 5 secondary alkyl, -CN, C 1 -C 5 alkoxy, and R 2 is H, F, Cl, C 1 -C 5 alkyl, C 3 -C 5 secondary alkyl, -CN, - CF 3, C 1 to C 5 alkoxy by reaction of dimethylamine with an arylisocyanate in an organic solvent medium characterized in that the reaction is carried out continuously in a column type reactor of at least 3 theoretical plates efficiency and residence time ranging from 0.5 to 30 minutes at 50 ° C to at the boiling point of the reaction mixture at a molar ratio of dimethylamine to aryl isocyanate of 0.95 to 1.20: 1.00, preferably 0.99 to 1.01: 1.00.