CS246648B1 - Process for preparing substituted arylguanamines - Google Patents

Abstract

where R^ denotes H, Cl, NH2, OCH3 and R2 is H, NO2, Cl, OCH3 or a CN group in position 4 or 5 by the reaction of an aromatic nitrile with dicyandiamide under catalysis by a basic catalyst such that the basic catalyzed reaction of the respective aromatic nitrile with dicyandiamide is carried out in an isobutanol environment, the catalyst being dosed into the reaction mixture in the form of an isobutanol solution, the mother isobutanol filtrate is recirculated directly to the following operation and after the production of the given arylguanamine is completed, isobutanol is regenerated from the mother filtrate.

Description

(54) A process for the preparation of substituted arylguanamines nh ₂

ⁿ 1

NH, wherein R 1 is H, Cl, NH ₂ , OCH _g and

R ₂ is H, NO ₂ , Cl, OCH ₃ or CN in the 4 or 5 position by reacting the aromatic nitrile with dicyandiamide under catalysis with a basic catalyst such that the base is catalyzed by reacting the corresponding aromatic nitrilt with dicyandiamide in rsobutanol. the catalyst is metered into the reacting mixture in the form of an isobutanol solution, the mother isobutanol filtrate is recirculated directly to the next operation, and after the production of the aryl aryl guanamine is finished, isobutanol is recovered from the mother filtrate.

The invention relates to a process for the preparation of substituted arylguanamines.

The preparation of substituted arylguanamines is described sporadically and generally very generally (1, 2, 3) in the literature. Substituted arylguanamines are prepared by reacting the corresponding arylnyl with dicyandiamide in 2-ethoxyethanol under KOH catalysis or under liquid ammonia under pressure.

Product separation is performed by diluting the reaction mixture with water, filtering off the product, and recovering 2-ethoxyethanol from the aqueous mixture. The use of ammonia as solvent requires autoclaving with an excess of aryl nitrile, and practical application of this procedure is only possible in special cases where unreacted aryl nitrile can be easily separated from the product.

It has now been found that the substituted arylguanamines of formula I

R ₁ NH ₂ where

R 1 is H, Cl, NH ₂ , OCH ₃ and

R ₂ H, NO ₂ , Cl, OCH 3, CN in the 4 or 5 position are preferably prepared according to the invention.

The process for the preparation of substituted arylguanamines by reaction of the aromatic nitrile with dicyandiamide under catalysis with a basic catalyst consists in carrying out the reaction in isobutanol and charging the basic catalyst in the form of an isobutanol solution in connection with the exothermic coloration of the reaction.

The cyclization itself is carried out by suspending the dicyandiamide and the corresponding arylnitrile at room temperature in a portion of isobutanol or in a recycled mother filtrate, and then heating the mixture to 90 ° C and starting to charge the isobutanol catalyst solution.

The reaction proceeds slowly at first and then very rapidly with increasing temperature, depending on the nature of the nitrile. After completion of the catalyst feed, the reaction mixture is kept under reflux for 3-4 hours. The reaction mixture was then cooled to 20-30 ° C and filtered on a suction filter.

The isobutanol filtrate obtained is used as part of the isobutanol charge for the following operation. The charge for further operations is then always constituted by a constant amount of dicyandlamide and arylnitrile. Only isobutanol and catalyst losses are added.

The filter cake is stirred and washed three times with boiling water (ca 98 ° C) and finally blown out with pressurized nitrogen. An additional portion of the crude arylguanamines is isolated from the aqueous filtrates after cooling by filtration and is added to the product after washing with a minimum of boiling water.

The product is dried in a vacuum oven at 110-120 ° C. After the series of arylguanamine preparations has been completed, the last mother filtrate in a stirred separator is washed with 30-40% sodium hydroxide solution, the organic layer is separated and isobutanol is recovered from it by rectification at atmospheric pressure. The reaction proceeds quantitatively in almost all cases, the potential losses being due only to the different water solubility of the individual arylguanamines during the washing.

The preparation of the above-mentioned substituted arylguanamines with recycle of the mother isobutanol filtrate can be carried out in conventional batch reactors equipped with a pressurized duplicator for emptying the reactor by nitrogen overpressure. Filtration and washing of the product on a suction with boiling water usually cause difficulties.

The examples below illustrate embodiments of the invention.

Example 1

51.35 g of o- (p-) chlorobenzonitrile (0.373 mol) and 39.1 g (0.465 mol) of dicyandiamide are suspended under vigorous stirring in 500 ml of isobutanol and the suspension is heated to 90 ° C.

A solution of 3.75 g of KOH in 100 ml of isobutanol is then added over 30 minutes.

Crystals of the product, i.e. o- (p-) chlorobenzoguanamine, are precipitated during dosing of the catalyst solution. The reaction is completed by heating to gentle boiling for 2 hours. After the reaction mixture has cooled to about 25 ° C, the crystalline product is separated by vacuum or pressure suction.

The filter cake is stirred three times on 200 ml of boiling water and immediately suctioned off sharply. The product after the third wash is dried at 110 ° C. Another portion of the product was isolated from the washings, which was cooled to 25 ° C, the crude product was filtered off, washed with 100 ml of boiling water and dried again at 110 ° C.

A total of 77.4 g of crystalline o- (p-) chlorobenzoguanamine is obtained, corresponding to 93.6% of theory for chlorobenzonitrile. The mother isobutanol filtrate is used as part of the isobutanol batch for the next operation, or after completion of a series of recycles, isobutanol from the last filtrate is regenerated as described above. At the same molar ratios of aryl nitrile and dicyandiamide, the preparation is carried out from nitriles substituted in the 4 or 5 position by CN or NO2. The procedure and yields of arylguanamines are comparable to Example 1.

Example 2

333.2 g of 2-amino-5-nitro-benzonitrile (95.3%) and 178.8 g of dicyandiamide were suspended in 1600 ml of isobutanol with stirring and heated to 100 ° C. 400 ml of 2.88 wt% are then introduced into the batch over 40 minutes. isobutanol solution of KOH.

During dosing of the catalyst solution, the color of the reaction of the mixture changes from ocher through carmine to a deep purple color, and the mixture thickens. The reaction is completed by heating the reaction mixture at gentle reflux for 2.5 hours.

After completion of the reaction, the reaction mixture is cooled to ca 25 ° C and the crude product is separated by suction. The mother isobutanol filtrate was treated in a similar manner to Example 1.

The filter cake is suspended in 1 liter of hot water ca 70 ° C, filtered and the isobutanol and aqueous layers are separated from the aqueous filtrate in a separator after cooling. The isobutanol layer is removed to recover isobutanol.

The aqueous layer is not treated. The washed filter cake is then washed on the suction with 800 ml of 5% ammonia water (obtained by absorbing NH4 in water from the off-gas in the actual reaction) and finally twice with 100 ml of boiling water (ca 98 DEG C.).

The product is dried in a vacuum oven at 100 ° C. The yield of 2,4-diamino-6- (2-amino-5-nitrophenyl) -1,3,5-triazine was ca 481 g, i.e. 99% of theory, to 100% of 2-amino-5-nitrobenzonitrile.

Example 3

388 g of o- (p -) - methoxybenzonitrile and 268 g of dicyandiamide are suspended with stirring in 1200 ml of isobutanol and heated to 100 ° C. Then, 2.88 wt. isobutanol solution of KOH.

After completion of the catalyst feed, the reaction mixture is kept under gentle reflux for 3 hours and then cooled to 25 ° C, the crude product is separated under suction. After subsequent washing of the cake with 400 ml of isobutanol, the combined isobutanol filtrates are recycled in the usual manner while the filter cake is washed with 400 ml of cold water.

The isobutanol layer is separated from the aqueous filtrate in a separator, which is led to the recovery of isobutanol. After a second washing of the cake with 400 ml of cold water again, the wet product is dried in a vacuum oven at 90 ° C. The yield of o-methoxybenzoguanamine without recycle of the mother isobutanol filtrate was 380 g, i.e. 60% of theory. Mp 242.5-244 ° C.

Claims (1)

A process for the preparation of substituted arylguanamines of formula (I) wherein H, Cl, NH ₂ , OCH ₃ and R ₂ is H, NO ₂ C 1, OCH or CN in the 4 or 5 position by reacting an aromatic nitrile with dikyandiamiden catalysis báziokým catalyst characterized in that the base-catalyzed reaction of corresponding aromatic nitrile with dicyandiamide carried out in an isobutanol, the catalyst into the reactive the isobutanol filtrate is re-recirculated directly to the next operation and isobutanol is recovered from the mother filtrate upon completion of the arylguanamine preparation.