CS243581B1 - Process for preparing 2-methyl-5-chloro-1,4-diaminobenzene - Google Patents

Abstract

Production of 2-methyl-5-chloro-1,4-diaminobenzene by reduction of a mixture of nitrochlorotoluenes obtained by nitration of 4-chlorotoluene by acylation of the resulting mixture of aminochlorotoluenes, nitration of the product and subsequent reduction and deacylation of a mixture of N-acylaminochloronitrotoluenes. The procedure relies on unexpectedly favorable substitution effects in the continuous development of a mixture of isomers during the entire synthesis.

Description

(54) A method for producing 2-methyl-5-chloro-1,4-diaminobenzene

Preparation of 2-methyl-5-chloro-1,4-diaminobenzene by reduction of the mixture of nitrochlortoluenes obtained by nitration of 4-chlorotoluene by acylation of the resulting mixture of aminochlortoluenes, nitration of the product followed by reduction and desacylation of the mixture of N-acylaminochlornitrotoluenes.

The process relies on unexpectedly favorable substitution effects in the continuous elaboration of a mixture of isomers throughout the synthesis.

The present invention relates to a process for the preparation of 2-methyl-5-chloro-1,4-diaminobenzene from 4-chlorotoluene nitration products.

2-Methyl-5-chloro-1,4-diaminobenzene finds utility in the synthesis of tar dyes, especially in the preparation of noble pigments with excellent thermostability (e.g., C.I. Pigment Yellow 93). It is prepared from 2-methyl-5-chloroaniline (so-called KB-amine), which is tosylated or acetylated and then nitrated, the resulting nitrodervate is detosylated or desacetylated and reduced to the desired 2-methyl-5-chloro-1, 4-diaminobenzene. The production of pure KB-amine starting material is technically demanding and its cost is relatively high.

According to the present invention, 2-methyl-5-chloro-1,4-diaminobenzene is produced from 4-chlorotoluene nitration products by treating the mixture of nitrochlortoluenes with reducing agents and then treating the resulting aminochlortoluenes with an acylating agent such as acetic acid, its anhydride or a chloride or ketene or a benzene-, toluene-naphthalenesulfonic acid chloride and then a nitrating agent optionally in an acid medium such as sulfuric or acetic, and then the mixture of N-acylaminochloronitrotoluenes is reduced and desacylated. Accordingly, the present invention is based on the treatment of a mixture of nitroisomers obtained by nitration of 4-chlorotoluene, and the sequence of synthetic steps can be represented by the following scheme:

Ac acyl

According to the invention, the following final reduction alternative can also be used:

The protected procedure relies on unexpectedly favorable substitution effects during the continuous processing of the mixture of isomers throughout the synthesis. Taking into account the fact that the starting 4-chlorotoluene is a raw material readily available and relatively inexpensive, the production according to the invention becomes very rational.

In the individual steps of the synthesis, the knowledge that has been practiced so far in the preparation of 2-methyl-5-chloro-1,4-diaminobenzene from KB-amine can be used.

The acylation can be carried out on the one hand by aliphatic carboxylic acids, their anhydrides or chlorides, such as acetic acid, acetic anhydride, acetyl chloride, on the other hand, aromatic sulfonic acid chlorides, for example benzenesulfonic acid chloride, toluenesulfonic acid, naphthalenesulfonic acid chloride, or the like. i ketenem.

In the treatment of N-acylaminochloronitrotoluenes, they can be reduced either directly and then desacylated, or desacylation first and then reducing the mixture of nitromethylchloranilines formed.

Example 1

To 177.0 g of a mixture containing 116.6 g of 2-methyl-5-chloroaniline, 52.4 g of 2-chloro-5-methylaniline and 8.0 g of water (mixture prepared by nitration of 4-chlorotoluene followed by hydrogenation of the mixture of nitroisomers to Pd / charcoal), 134.6 g of 95% acetic anhydride are added under stirring; the temperature spontaneously rises to 121 ° C. Within 20 min. 250 ml of water are added while the reaction mixture is boiling. A further 320 ml of water are then added; the temperature drops to 60 ° C. The resulting suspension is cooled to 20 ° C, the crystalline fraction is filtered off and washed with 600 ml of water, suctioned vigorously and dried at 80 ° C in a hot-air oven. To 835.0 g of 97% sulfuric acid, while stirring, a mixture of dried N-acetylmethylchloranilines is added in portions such that the temperature does not exceed 20 ° C, then the reaction mixture is cooled to 5 ° C, followed by addition of nitration acid prepared by mixing. 350.0 g 97% sulfuric acid and 75.3 g 98% nitric acid; the temperature is maintained below 10 ° C during 3-hour nitration. After one hour hold at 10 to 15 C ^and poured onto 1300 ml water and 1150 g of ice. The resulting nitro compound suspension is filtered - after stirring for 0.5 h - and the solids are dehydrated by washing with 25 L of water. A 35% paste of the nitro products is obtained.

620 ml of water are charged into the reactor, 3.3 g of surfactants (e.g. polyhydroxyethylated phenol) and all past nitration paste are added; The suspension is stirred for 4 hours. 835 ml of water are poured into the reducer, 206.0 g of iron filings are added and 13.1 g of 85% formic acid are added. The mixture is heated to boiling and sawdust is etched for 1 h. The prepared nitro compound suspension is then added portionwise at 40 ° C over 40 min, then the reaction mixture is stirred at 100 ° C for 1 h. Iron is precipitated by the addition of 40.0 g of magnesite meal, the content of the reducer is diluted to 8 L with water, heated to 113 ° C, and at this temperature the iron sludge is filtered off and washed with 850 ml of hot water. The product is cooled from the combined filtrates by cooling and the 20 ° C suspension is filtered, the cake is washed with 650 ml of water and drained sharply. A 40% paste of N-acetylchloromethyl-1,4-phenylenediamines is obtained.

860 ml of water is poured into the reactor and all the paste obtained from the reduction is added. 140.1 g of 97% sulfuric acid are added under stirring with a thin stream, the mixture is heated to 100 ° C and stirred at this temperature for 3 hours. The mixture was cooled from the outside bath while calcined soda was added until a pH of 5.5 was reached. The resulting 2-methyl-5-chloro-1,4-diaminobenzene suspension was cooled to 20 ° C, filtered and washed with 300 mL water. The paste obtained shows a dry matter content of 35.1% (the remainder being predominantly sodium sulphate) and a yield of 52.8% of theory based on the mixture of methyl chloranilines employed.

When acetyl chloride equivalent is used in place of acetic anhydride for acylation, the yield is the same. Acylation with acetic acid can be carried out as in the known preparation of acetanilide.

If the Béchamp reduction is replaced by hydrogenation, for example at a hydrogen pressure of 20 bar at a temperature of 90 ° C for 4 hours, the yield increases by 8.5% of theory.

Example 2

Κ 1,400 ml of water heated to 70 ° C are added 296 g of a mixture containing 183 g of 2-methyl-5-chloroaniline, 100 g of 2-chloro-5-methylaniline and 13 g of water (mixture obtained by hydrogenation of products from nitration of 4- chlorotoluene under Raney nickel catalysis, then 1,609 g of a neutral suspension of p-toluenesulfochloride (prepared by mixing 500 ml of water, 484 g of crude, triturated p-toluenesulfochloride with acidification by soda) were added at 75 ° C. With vigorous stirring at 80 ° C, the acidity of the reaction mixture is blunted by the addition of sodium carbonate solution to pH 7 + 0.5; after 0.5 h, tosylation is complete. The coarse-crystalline tosyl derivative is precipitated by adding 200 g of sodium hydroxide and precipitating the tosyl derivative from the resulting solution at 25 [deg.] C. by adding 270 g of conc. at 25 DEG C., the tosyl derivative is precipitated by the addition of 270 g of terminal hydrochloric acid; the temperature is kept below 30 ° C. Then, the suspension is filtered and the cake washed with 3.5 L of water.

The resulting N-tosylated chloromethylaniline paste is stirred with 2.7 l of water, 164.8 g of 65% nitric acid and 2 g of sodium nitrite and 8 g of alkyl polyglycol ether. The mixture was heated to 90 ° C with stirring and held at this temperature for 12 hours. The cooled suspension was filtered at 20 ° C and the solid was washed with 3 L of water. A paste of N-tosylated chloronitromethylanilines is obtained.

This paste is added in portions to 1,470 g of 96% sulfuric acid heated to 45 ° C; with stirring, the temperature of the mixture rose to 125 ° C. After 10 min, the resulting solution was cooled to 100 ° C and poured into 7 L of water at 40 ° C over 5 min with vigorous stirring. The reaction mixture is heated at 80 ° C to 80 ° C, then cooled to 20 ° C, the resulting suspension is filtered and the cake washed with 4.3 L of water. A nitrochloromethylaniline paste is obtained.

A suspension is prepared from the paste by mixing with 5.4 L of water. 274 g iron and 110 g conc. The hydrochloric acid is heated to boiling with stirring, kept under boiling for 0.5 h, 5.5 l of hot water are added, and the suspension obtained is added in portions while keeping the mixture boiling. The reduction is complete after 2 h. 1 L of cold water is added to the reaction mixture and the suspension is filtered at 90 ° C. The separated ferric sludge was washed with 1.5 L of hot water. From the combined filtrates, 2-methyl-5-chloro-1,4-diaminobenzene is precipitated by cooling, whose total content in the filtrate is 1.290 moles, ie 64.5% of theory, based on the isomeric methylchloraniline mixture employed.

If the aqueous suspension of nitrochlormethylaniline paste is hydrogenated instead of iron reduction (4 MPa hydrogen, Pd / carbon catalyst, temperature 120 ° C), 1.385 mol of 2-methyl-5-chloro-1,4-diaminobenzene is obtained, i.e. 69.3%. theory calculated per seed mixture of isomeric methylchloranilines.

When the aqueous suspension of the obtained paste of N-tosylated chloronitromethylanilines is first hydrogenated and then detosylated, the yield is 66.3% of theory.

Claims (4)

Subject Process for the preparation of 2-methyl-5-chloro-1,4-diaminobenzene from 4-chlorotoluene nitration products, characterized in that the mixture of nitrochlortoluenes is treated with reducing agents, and the resulting aminochlortoluenes are treated with an acylating agent such as acetic acid, its anhydride or a chloride or ketene or a benzene, toluene or naphthalenesulfonic acid chloride and then a nitrating agent optionally in an acid medium such as sulfuric or acetic, and then the mixture of N-acylaminochloronitrotoluenes is reduced and desacylated. 2. Process according to claim 1, characterized in that the reduction is carried out after the desacylation of the N-acylaminochloronitrotoluenes. 3. The process according to claim 1, wherein the reduction of the nitrochlortoluene mixture and then the N-acylaminochloronitrotoluene mixture, optionally desacylated, is carried out with iron in an aqueous medium in the presence of electrolytes according to the procedure defined as Béchamp reduction. 4. A process according to claim 1, wherein the reduction of the nitrochlortoluene mixture and then the N-acylaminochloronitrotoluene mixture, optionally desacylated, is carried out with hydrogen in the presence of hydrogenation catalysts.