IL108963A - Process for the preparation of 3,4'-diaminodiphenyl ether - Google Patents

Description

REF : 2887/93 PROCESS FOR THE PREPARATION OF 3.4' - DIAMINODIPHENYL ETHER PROCESS FOR THE PREPARATION OF 3.4'-DIAMINODIPHENYL ETHER Field of the Invention This invention relates to a process for the preparation of 3,4'-diaminodiphenyl ether from easily available, commercial starting compounds.

Background of the Invention 3,4'-diaminodiphenyl ether (hereinafter indicated also as 3,4'-DADPE) is a monomer useful as a component for aromatic polyimides, polyamides and aramid fibers. A number of methods have been described in the art for the preparation of 3,4'-DADPE, but they are not fully satisfactory. One such method is based on the condensation of 3-aminophenol and 4-nitrochlorobenzene in the presence of an aprotic polar solvent and an alkali metal carbonate, with heating and elimination of water by distillation. Such a method is described, e.g., in JP 85-66096, JP 85-60832, JP 85-105649 and JP 89-272558. It is suggested that in a similar process, 3-nitrophenol be used instead of 3-aminophenol as a starting material. Subsequently the 3,4'-dinitrodiphenyl ether obtained is hydrogenated over Pd/C [JP 86-221157]. 3,4'-DADPE obtained by the reduction of dinitrodiphenyl ether or nitro amino diphenyl ethers contains heavy products (organic impurities having boiling points higher than that of 3,4'-DADPE), which are decomposed during distillation affording low boiling aniline derivatives [JP 89-272558]. In order to prepare 3,4'-DADPE of high purity, it is necessary to carry out two distillations - rough distillation to remove the heavy products, followed by fractional distillation.

JP 86-140550 describes the preparation of 3,4'-DADPE by XJllmann reaction of 4-iodoaniline and 3-aminophenol in the presence of copper iodide, KOH and dimethylsulfoxide. However, the yield of the desired product is low - about 50% - and the starting iodoaniline is not a commercial product.

A number of patents describe the preparation of 3,4'-DADPE by treating 3,4'-dichlorodiphenyl ether with ammonia in the presence of copper catalysts. In particular, JP 63-22059 and .01-85951 describe such an amination. No data are reported in these references concerning the isolation and purification of the cal 3,4'-DADPE. As seen from the examples given in JP 63-22059, the conversion of 3,4'-dichlorodiphenyl ether did not exceed 93% and the selectivity for 3,4'-DADPE was 80-87%. The yield of 3,4-DADPE given in JP 01-85951 was less than 50%.

It is a purpose of this invention to provide a new route foE the preparation of 3,4'-DADPE which starts from easily available comi&fercial products, involves only a few steps, and provides the final 3,4'-DADPE in high yields and with good purity.

Other purposes and advantages , of the invention will better appear as the description proceeds.

Summarv of the Invention The invention provides a process for the preparation of 3,4'-DADPE which comprises the preparation of 4-bromo-3'-chlorodiphenyl ether (hereinafter also designated as BCDPE) and its animation, followed by fractional distillation of 3,4'-DADPE obtained to produce the final pure product. 4-Bromo-3'-chlorodiphenyl ether is prepared by bromination of 3-chlorodiphenyl ether (hereinafter also designated as 3-CDPE). The bromination is preferably carried out with liquid bromine solution in dichloromethane at temperatures from -60°C to 0°C and preferably from -50°C to -30°C 3-CDPE is obtained preferably by Ullmann condensation of 1 ,3-dichlorobenzene (hereinafter also designated as DCB) with phenol. The condensation of DCB with phenol is carried out in an aprotic polar solvent, such as N,N-dimethylformamide, Ν,Ν-dimethylacetamide, N-methylpyrrolidone, preferably dimethylsulfoxide in the presence of an alkali, such as KOH, K2CO3, preferably NaOH and a copper catalyst, preferably copper (I) chloride at a temperature of 160-175°C, preferably 170-173°C. The copper catalyst content is 0.5-30% mol, preferably 1-4% mol with respect to phenol. The amount of dimethylsulfoxide is 20 to 200% w. per phenol, preferably 60-100% w. The molar ratio DCB: phenol is from 4:1 to 15:1, preferably from 7:1 to 11 :1.

The amination of BCDPE is preferably carried out by means of aqueous ammonia in the presence of a copper catalyst, such as copper (I) chloride, copper (I) oxide, and preferably, copper (II) sulfate. The amount of the copper catalyst used is 0.1-1 mol, preferably 0.2-0.3 mol, based on 1 mol BCDPE. Concentration of aqueous ammonia is comprised between 20 and 40% w., and preferably between 25 and 33%w. The molar ratio ammonia: BCDPE is 10-30, preferably 12-16. The . amination temperatures are comprised between 180°C and 240°C, and preferably between 185°C and 230°C.

The crude 3,4'-DADPE thus obtained is purified by means of fractional distillation, under the following conditions: 5-20 theoretical stages, preferably 8-12; reflux ratio 0-20, preferably 1-10; top pressure 0.3-5 mm Hg, preferably 0.5-3 mm Hg; top temperature for the main fraction (pure 3,4'-DADPE) 180-233°C, bottom temperature 235-290°C, preferably not more than 280°C. The fractional distillation is carried out in the presence of an alkali such as sodium hydroxide or potassium hydroxide, as will be described hereinafter.

Detailed Description of Preferred Embodiments The process according to the invention provides 3,4'-diaminodiphenyl ether in good yields and with good purity from inexpensive and easily available raw materials, such as dichlorobenzene, phenol and bromine. The first stage of the process is an Ullmann reaction, and is well known [USP 3,371 ,120, JP 62-281837, JP 63-41434, DE 3940130, EPA 9011029.7, USP 4,766,253, USP 3,567,783 and EPA 0 051235]. Examples of the three stages of the process leading to the preparation of 3,4'-DADPE are given below.

Kxample 1 Preparation of 3-chIorodiphenyl ether Ullmann reaction 40.8 g (1.02 mol) of sodium hydroxide are added to a solution of 94 g (1 mol) of phenol in 1470 g (10 mol) of DCB and 94 g (1.2 mol) of DMSO. The mixture is heated with stirring and at the temperature of 120-140°C water starts to separate. The internal temperature is continuously raised to 170-173°C (b.p. of DCB). After water is completely removed by means of a special water separator (inverse Dean-Stark trap), 2 g of CuCl are added and the reaction mixture is allowed to react to completion, with vigorous stirring, at 170-173°C, under a nitrogen atmosphere for 1-2 hours. Final GC analysis showed an absence of phenol.

After cooling, the mixture is filtered to separate sodium chloride formed and copper catalyst (~60 g). The organic phase is worked up by distillation under vacuum. The first fraction (30-50 mm Hg, 80-120°C) consists of the unreacted DCB and dimethylsulfoxide. The target fraction (30 mm Hg, 167°C) represents 3-chlorodiphenyl ether in a quantity of 176 g (86% yield with respect to phenol) and a purity of -99%.

Example 2 Bromination of 3-CDPE Into a suitable reaction vessel fitted with a stirrer and a dropping funnel, there is charged 102.2 g (0.5 mol) of 3-CDPE and 400 ml of dichloromethane. The mixture is cooled to about -45°C, followed by the slow addition of 96 g bromine in 100 ml of dichloromethane. After completing the bromination, traces of unreacted bromine are neutralized with sodium bisulfite aqueous solution. The resulting mixture is distilled under vacuum to give BCDPE (0.2 mm Hg, 115°C) in a quantity of 113 g (80% yield) with a purity of -99%. Excess of bromine is necessary in order to convert undesirable isomer 4-bromo-3-chlorodiphenyl ether (formed during the bromination of 3-CDPE) to 4,4'-dibromo-3-chlorodiphenyl ether, which is easily separated from BCDPE.

Example 3 Amination of BCDPE Into a Parr vessel (0.45 liter) were introduced 70 g of BCDPE (0.247 mol), aqueous 25% ammonia (235 g, 3.45 mol) and CuS04-5H20 (15.4 g, 0.062 mol). The mixture was stirred at 600 psi for 2 hours at 190°C and then for 5 hours at 230°C at 800-1100 psi. After the reaction was complete, the reaction mixture was cooled to 60°C.

The upper, aqueous layer, containing unreacted NH3, ammonium chloride formed and copper catalyst, was separated. Lower organic phase, representing the crude 3,4'-DADPE, was washed in the autoclave successively with 100 ml of 25% NH3 aqueous solution and 150 ml of water to remove remaining ammonium chloride and copper catalyst. The washed liquid product was then drained from the bottom of the reactor at 60°C. After water was distilled off at 90-100°C under reduced vacuum, 45 g of crude product with a 3,4'-DADPE content of 90-93% (according to gas chromatography) was obtained. Along with 3,4'-DADPE, up to 5-7% of 4-amino-3'-hydroxy- and 3-amino-4'-hydroxydiphenyl ethers form as the products of the partial hydrolysis of BCDPE. This crude 3,4'-DADPE was purified by one vacuum distillation to afford a final pure 3,4'-DADPE.

Example 4 Purification of 3,4*-DADPE Crude amination product (45 g) containing 90-93% (GC) of the 3,4'-DADPE was distilled fractionally by means of a distillation column with 8 theoretical stages and equipped with a distillation head. The conditions were: top pressure of 1 mmHg, bottom pressure of 5 mm Hg, top temperature of 137-210°C and bottom temperature of 238-279°C. The distillation was performed in the presence of NaOH taken in an amount of 3% w. per crude 3,4'-DADPE. Addition of alkali metal hydroxide is necessary to turn hydroxyaminodiphenyl ethers into their alkali salts. As a result, hydroxyaminodiphenyl ethers remain at the bottom of the reboiler during the distillation.

The first fraction (3 g) of top temperature of 137-201°C (reflux ratio 9) represents the mixture consisting of so-called light impurities in crude 3,4'-DADPE, such as aniline, aminophenols, mono amino diphenyl ethers and 3-chloroaminodiphenyl ether, which is a product of incomplete amination of BCDPE. The principle fraction (36 g) of top temperature of 207-210°C (reflux ratio 1) was 3,4'-DADPE of 99.9% purity, according to gas chromatography. The yield of the pure 3,4'-DADPE was of 73% with respect to BCDPE.

While an embodiment of the invention has been described by way of illustration, it would be clear that the invention may be carried into practice with many modifications, variations and adaptations, without departing from its spirit or exceeding the scope of the claims. 2887/93 108963/2

Claims (14)

1. ) Process for the preparation of 3,4'-diaminodiphenyl ether, which comprises the preparation of 4-bromo-3'-chlorodiphenyl ether and its amination in aqueous solvent and in the presence of a catalyst, followed by purification of 3,4'-diaminodiphenyl ether.

2. ) Process according to claim 1 wherein amination of 4-bromo-3'-chlorodiphenyl is effected by reaction with an aqueous solution of ammonia.

3. ) Process according to claim 1 wherein the catalyst is a copper compound.

4. ) Process according to claim 3 wherein the copper compound is chosen from among copper (II) sulfate, copper (I) chloride and copper (I) oxide.

5. ) Process according to claim 1 wherein the amount of copper catalyst used is 0.1-1 mol based on 1 mol of 4-bromo-3'-chlorodiphenyl ether.

6. ) Process according to claim 1 wherein the concentration of ammonia in its aqueous solution is 20-40% w.

7. ) Process according to claim 1 wherein the molar ratio ammonia per 4-bromo-3'-chlorodiphenyl ether is 10-30. 2887/93 -10-

8. - Process according to claim 2, wherein the amination is carried out at v/ temperatures from 180 to 240°C.

9. - Process according to claim 1, wherein the 4-bromo-3'-chlorodiphenyl ether is prepared by bromination of 3-chlorodiphenyl ether.

10. - Process according to claim 1 , wherein the bromination of 3-chlorodiphenyl ether is effected with liquid bromine solution in dichloromethane at temperatures from -60 to 0°C.

11. - Process according to claim 9, wherein the 3-chlorodiphenyl ether is obtained by condensation of 1,3-dichlorobenzene with phenol.

12. - Process according to claim 11, wherein the condensation is carried out in an aprotic polar solvent in the presence of an alkali and a copper catalyst.

13. - Process according to any one of claims lto 12, further comprising the purification of the crude 3,4'-diaminodiphenyl ether by one fractional distillation.

14. - Process according to any one of claims 1 to 13, substantially as described and exemplified. LUZZATTO * tOZZATTO :>"V