GB1575860A

GB1575860A - Process for the manufacture of m-aminophenols

Info

Publication number: GB1575860A
Application number: GB1265778A
Authority: GB
Original assignee: Hoechst AG
Current assignee: Hoechst AG
Priority date: 1977-03-31
Filing date: 1978-03-31
Publication date: 1980-10-01
Also published as: JPS53121728A; DE2714255A1; FR2385683A1

Description

(54) PROCESS FOR THE MANUFACTURE OF M-AMINOPHENOLS (71) We, HOECHST AKTIENGESELLSCHAFT, a body corporate organised according to the laws of the Federal Republic of Germany, of 6230 Frankfurt/Main 80, Postfach 80 03 20, Federal Republic of Germany, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to the manufacture of m-aminophenols.

m-Aminophenols are valuable starting compounds for the manufacture of dyestuffs, optical brighteners and antioxidants. They can be prepared by reacting resorcinol (1,3-dihydroxybenzene) with ammonia or a primary or secondary aliphatic or aromatic amine (cf. U.S. Patent Specifications Nos. 2,376,112, 3,102,913 and 3,450,764; German Patent Specifications Nos. 121,683 and 49,060, and German Offenlegungsschrift No.

1,543,368 The present invention provides a process for the manufacture of m-aminophenols, which comprises reacting resorcinol with ammonia or a primary or secondary amine in the presence of a catalytic amount of at most 0.05 mol of phosphoric acid or a salt thereof per mol of resorcinol.

The phosphoric acid or salt thereof is preferably used in an amount of from 0.001 to 0.02 mol for each mol of resorcinol; within the indicated limits the amount of catalyst to be used in each case is not critical. For practical reasons it is generally preferred to use as low as possible an amount of catalyst. Phosphoric acid is the preferred catalyst. Preferred salts of phosphoric acid are those with weak bases, especially a salt with ammonia or a primary or secondary amine used as a starting component.

Phosphoric acid is generally used in a concentrated, water-containing form. Instead of phosphoric acid itself there may also be used oligomers thereof, polyphosphoric acids, or salts thereof, preferably the amine or ammonium salts. Mixtures of two or more of the catalysts may be used.

To carry out the process of the invention generally 1 mol of resorcinol is reacted with at least one mol of a primary or secondary amine or ammonia in the presence of, for example, from 0.001 to 0.02 mol of phorphoric acid or an amine or ammonium salt thereof, at an elevated temperature, preferably in the range of from 1500 to 250"C.

Depending on the type of the amine component and its volatility, optimum reaction conditions can be chosen for each individual case. When using a relatively involatile amine, for example a primary aromatic amine such as aniline or a substituted aniline, it is advantageous, for example, to carry out the reaction by mixing 1 mol of resorcinol with approximately 1.2 mol of aniline or aniline derivative and 0.007 mol of phosphoric acid or the aniline salt thereof, and slowly heating the mixture to a temperature in the range of from 1800 to 200"C while stirring. In general, the reaction starts at that temperature and the respective 3-hydroxydiphenyl amine is formed with separation of water. The process of the reaction can be readily determined from the amount of water distilled off. When the reaction is complete, the 3-hydroxydiphenyl amine can be obtained in the pure state and in a good yield by vacuum distillation.

More readily volatile amines, for example dimethyl amine, can be reacted with resorcinol and the catalytic amount of phosphoric acid or salt thereof in an autoclave at approximately 200"C to give 3-dimethylaminophenol. For this reaction either a commercial aqueous dimethyl amine solution (for example of 40 or 60% strength) or anhydrous dimethyl amine can be used. When using an aqueous solution the reactants can be mixed with one another and then heated to reaction temperature over a period of approximately 1 hour. The reaction takes place without a significant temperature increase. When using anhydrous dimethyl amine, it is advantageous to add the amine in small quantities to a mixture of resorcinol and the phosphoric acid catalyst at a temperature in the range of from 1500 to 1600C, and to control in this manner the exothermal course of the reaction. When the reaction is complete excess dimethyl amine, if any, and the reaction water can be distilled off. Depending on the intended use, the 3-dimethylaminophenol can be purified by vacuum distillation or in some cases the crude product may be used directly for further reactions.

This is especially advantageous for the synthesis of some phenoxazin dyes (cf., for example, German Auslegeschrift No. 2,458,347) wherein the nitrosation of the crude product which may be obtained according to the present invention is possible without previous purification.

In the process of the invention there can be used, besides ammonia, all primary or secondary amines, for example aliphatic, aromatic, araliphatic, or heterocyclic amines, that are stable under the reaction conditions, as well as corresponding substituted amines.

Preferred amine components are, for example, ammonia, methylamine, dimethyl amine, ethyl amine, aminoethanol, butyl amine, dibutyl amine, aniline, chloroaniline, toluidine, anisidine. N-methylaniline, xylidene, cyclohexyl amine and aminophenol, dimethyl amine being especially preferred.

The amines are generally used in stoichiometric amounts, calculated on the resorcinol. In some cases a small excess, sometimes even a large excess, of the amine may be advantageous, the excess possibly being in the range of from a fraction of to one or more times the molar amount of the stoichiometrically required amount.

The process of the invention may be carried out in the presence of an inert organic solvent, which may be used in a usual amount, for example from 0.5 to five times the amount of resorcinol. Suitable solvents are, for example, aromatic, araliphatic or aliphatic hydrocarbons, higher alcohols or ethers. The process of the invention is, however, preferably carried out in the absence of inert organic solvents, which in part are readily combustible, so that it has a much smaller polluting effect on the environment and, because of the saving of volume, the spaced-time-yield of the apparatus used is considerably increased.

Compared with known processes for the manufacture of 3-aminophenols from resorcinol and amines in the presence of various condensing agents, the process of the invention is characterised by the use of very small, catalytic amounts, of preferably aqueous phosphoric acid, by an especially simple mode of operation and its non-polluting and anticorrosive effect, and a high conversion rate of the reactants to substantially uniform reaction products. Because the process is preferably carried out in the absence of combustible solvents and toxic substances the space-time-yield of the apparatus used is considerably increased.

The present invention also provides a process for preparing an oxazine dyestuff, wherein a m-aminophenol prepared acording to the invention is treated, without intermediate purification, with nitrous acid to introduce a nitroso group and the product is condensed with a m-phenylenediamine, and a process for preparing a xanthene dyestuff, wherein a m-aminophenol as above is condensed, without intermediate purification, with a 2-hydroxy-4-dialkylamino-benzophenone-2'-carboxylic acid.

The following Examples illustrate the invention.

Example 1 In a three-necked flask fitted with a stirrer, thermometer and water separator, 560 g of resorcinol (98.9% strength), 738 g of p-anisidine and 4 g of phosphoric acid (85% strength) were heated. The reaction started at 194"C with the separation of water. During the course of about 3 hours the temperature was raised to 220"C, whilst 90 ml of water were collected in the water separator. The p-anisidine in excess and a little resorcinol were then distilled off under reduced pressure (0.3 torr) at the sump temperature of up to 220"C. At a sump temperature in the range of from 220 to 230"C and a head temperature of 210 to 218"C 3-hydroxy-4'-methoxydiphenylamine of the formula

distilled over into a receiver in an amount of 915 g, corresponding to a yield of about 85% of the theory, calculated on the resorcinol used.

Example 2 560 g of resorcinol (98.9% strength), 642 g of p-toluidine and 4 g of phosphoric acid (85% strength) were heated as described in Example 1. After the separation of 90 ml of water, the product was distilled under reduced pressure. At 0.5 torr first unreacted p-toluidine distilled over. 880 g of 3-hydroxy-4'-methyldiphenylamine of the formula

were then obtained at a sump temperature of 192" to 230"C and a head temperature of 185 to 1950C. Yield: 88.4% of the theory.

Example 3 In a 2 litre steel autoclave with. electrical heating 667 9 of resorcinol (98.9% strength), 462 g of aqueous dimethyl amine solution (60% strength and 5 g of phosphoric acid (85% strength) were heated to 2000C during the course of 1 hour and maintained at that room temperature for about 12 hours. The pressure decreased from initially about 20 kg/cm2 to 14 kg/cm2. After completion of the reaction, the unreacted dimethyl amine and the water were distilled off and the oily/waxy reaction product was subjected to a vacuum distillation. At a sump temperature of 135 to 140"C and a head temperature of 132" to 1340C there were obtained at about 3 torr 687 g of 3-dimethylaminophenol of the formula

solidifying in the form of light crystals and having a content of pure substance of 83%, corresponding to a yield of about 69% of the theory, calculated on the resorcinol.

If the 3-dimethylaminophenol prepared as described above is used for the manufacture of phenoxazin dyes according to' German Offenlegungsschrift No. 2,458,347, its purification by vacuum distillation can be dispensed with and the crude product, freed from dimethyl amine and water, can be directly subjected to the nitrosation.

Example 4 In an autoclave fitted with a stirrer, temperature measurement and gas inlet, 1,320 g of resorcinol (98.9% strength) 10 g of phosphoric acid (85% strength) and 300 g of gaseous dimethyl amine were heated to 140"C while stirring. Heating was then discontinued.

Thereafter the temperature rose automatically to 210 to 220"C with adjustment of a pressure of 20 to 23 bar. After 1 hour the pressure of the autoclave was released at 2000C in order to remove the water formed from the reaction equilibrium. A further 200 g of gaseous dimethylamine were introduced into the autoclave and the reaction mixture was again heated to 2100C. The mixture was maintained at this temperature for 1 hour and thereafter the pressure was again released. After depressurisation of the autoclave a further 100 g of gaseous dimethyl amine were introduced and the mixture was maintained for 1 hour at 210 C. The reaction mixture solidified at room temperature and contained 76% of the theory of 3-dimethylaminophenol, which could be worked up in the manner described in Example 3.

WHAT WE CLAIM IS: 1. A process for the manufacture of a m-aminophenol, which comprises reacting resorcinol with ammonia or a primary or secondary amine in the presence of a catalytic amount of phosphoric acid or a salt thereof, the amount of phosphoric acid or salt thereof being at most 0.05 mol per mol of resorcinol.

2. A process as claimed in claim 1, wherein the phosphoric acid or salt there of is used in an amount of from 0.001 to 0.02 mol per mol of resorcinol.

3. A process as claimed in claim 1 or claim 2, wherein a phosphoric acid salt is a salt of phosphoric acid with a weak base.

4. A process as claimed in claim 3, wherein a phosphoric acid salt is a salt of phosphoric acid with ammonia or a primary or secondary amine.

5. A process as claimed in any one of claims 1 to 4, wheren a phosphoric acid oligomer or polyphosphoric acid, or a salt thereof, is used as catalyst.

6. A process as claimed in any one of claims 1 to 5, wherein the amine is a primary or secondary, aliphatic, aromatic, araliphatic or heterocyclic amine.

7. A process as claimed in claim 6, wherein the amine is any one of those specifically mentioned herein.

8. A process as claimed in claim 7, wherein resorcinol is reacted with dimethyl amine.

9. A process as claimed in any one of claims 1 to 8, wherein the reaction is carried out at a temperature in the range of from 1500 to 250"C.

10. A process as claimed in claim 1, conducted substantially as described herein.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

Example 2

560 g of resorcinol (98.9% strength), 642 g of p-toluidine and 4 g of phosphoric acid (85% strength) were heated as described in Example 1. After the separation of 90 ml of water, the product was distilled under reduced pressure. At 0.5 torr first unreacted p-toluidine distilled over. 880 g of 3-hydroxy-4'-methyldiphenylamine of the formula

were then obtained at a sump temperature of 192" to 230"C and a head temperature of 185 to 1950C. Yield: 88.4% of the theory.

Example 3 In a 2 litre steel autoclave with. electrical heating 667 9 of resorcinol (98.9% strength), 462 g of aqueous dimethyl amine solution (60% strength and 5 g of phosphoric acid (85% strength) were heated to 2000C during the course of 1 hour and maintained at that room temperature for about 12 hours. The pressure decreased from initially about 20 kg/cm2 to 14 kg/cm2. After completion of the reaction, the unreacted dimethyl amine and the water were distilled off and the oily/waxy reaction product was subjected to a vacuum distillation. At a sump temperature of 135 to 140"C and a head temperature of 132" to 1340C there were obtained at about 3 torr 687 g of 3-dimethylaminophenol of the formula

solidifying in the form of light crystals and having a content of pure substance of 83%, corresponding to a yield of about 69% of the theory, calculated on the resorcinol.

If the 3-dimethylaminophenol prepared as described above is used for the manufacture of phenoxazin dyes according to' German Offenlegungsschrift No. 2,458,347, its purification by vacuum distillation can be dispensed with and the crude product, freed from dimethyl amine and water, can be directly subjected to the nitrosation.

Example 4 In an autoclave fitted with a stirrer, temperature measurement and gas inlet, 1,320 g of resorcinol (98.9% strength) 10 g of phosphoric acid (85% strength) and 300 g of gaseous dimethyl amine were heated to 140"C while stirring. Heating was then discontinued.

Thereafter the temperature rose automatically to 210 to 220"C with adjustment of a pressure of 20 to 23 bar. After 1 hour the pressure of the autoclave was released at 2000C in order to remove the water formed from the reaction equilibrium. A further 200 g of gaseous dimethylamine were introduced into the autoclave and the reaction mixture was again heated to 2100C. The mixture was maintained at this temperature for 1 hour and thereafter the pressure was again released. After depressurisation of the autoclave a further 100 g of gaseous dimethyl amine were introduced and the mixture was maintained for 1 hour at 210 C. The reaction mixture solidified at room temperature and contained 76% of the theory of 3-dimethylaminophenol, which could be worked up in the manner described in Example 3.

WHAT WE CLAIM IS: 1. A process for the manufacture of a m-aminophenol, which comprises reacting resorcinol with ammonia or a primary or secondary amine in the presence of a catalytic amount of phosphoric acid or a salt thereof, the amount of phosphoric acid or salt thereof being at most 0.05 mol per mol of resorcinol.
2. A process as claimed in claim 1, wherein the phosphoric acid or salt there of is used in an amount of from 0.001 to 0.02 mol per mol of resorcinol.
3. A process as claimed in claim 1 or claim 2, wherein a phosphoric acid salt is a salt of phosphoric acid with a weak base.
4. A process as claimed in claim 3, wherein a phosphoric acid salt is a salt of phosphoric acid with ammonia or a primary or secondary amine.
5. A process as claimed in any one of claims 1 to 4, wheren a phosphoric acid oligomer or polyphosphoric acid, or a salt thereof, is used as catalyst.
6. A process as claimed in any one of claims 1 to 5, wherein the amine is a primary or secondary, aliphatic, aromatic, araliphatic or heterocyclic amine.
7. A process as claimed in claim 6, wherein the amine is any one of those specifically mentioned herein.
8. A process as claimed in claim 7, wherein resorcinol is reacted with dimethyl amine.
9. A process as claimed in any one of claims 1 to 8, wherein the reaction is carried out at a temperature in the range of from 1500 to 250"C.
10. A process as claimed in claim 1, conducted substantially as described herein.
11. A process as claimed in claim 1, conducted substantially as described in any one of

the Examples.
12. A m-aminophenol whenever prepared by a process as claimed in any one of claims 1 to 11.
13. A process for preparing an oxazine dyestuff, wherein a m-aminophenol as claimed in claim 12, is treated, without intermediate purification, with nitrous acid to introduce a nitroso group and the product is condensed with a m-phenylene diamine.

-14. A process for preparing a xanthene dyestuff, wherein a m-aminophenol as claimed in claim 12 is condensed, without intermediate purification, with a 2-hydroxy-4 dialkylamino-benzophenone-2'-carboxylic acid.