SK140689A3 - Preparation method of the primary aromatic amines and/or diamines - Google Patents

Abstract

The procedure described in this patent is provided based on the catalytic carbonylation reaction of aromatic nitro or dinitro compounds, while gas containing carbon monoxide and water is acting at the temperature of 80 up to 300 Celsius degrees (130 up to 200 Celsius degrees) and at the pressure of 0,1 up to 30 MPa, however the catalytic system is based on the sulphur or sulphur compounds with molar weight of 34 up to 140 g.mol-1, together with alkaline salt of carboxyl acid, C1 up to C6, as sodium acetate CH3COONa and vanadium oxide or iron oxide, or the supplementary checked and controlled admixtures of oxygen in the quantity of 0,1 up to 7 weight percent closed to aromatic nitro compounds and aliphatic amine with alkyl C1 up to C6, primary aromatic amine and morpholine, while it is suitable a part of the produced amines to be recirculated.

Description

In this case, the weight of the weight will not be higher.

The preparation of aniline from nitrobenzene and, analogously, other aromatic amines from the corresponding nitro compounds by their reduction with chemical agents is known. Thus, the reducing agent is zinc in an alkaline medium and in acidic, the iron in the presence of electrolytes (ie. Béchamp reduction), and sulfides of alkali metals and polvsulí ^{telephone. However, these spacings require significant minimum stoichiometric amounts of reducing agents / Weissermel, Arpe: Industrial Organic Chemistry, SNTL Prague (1985); Hrušovský M. et al.: Organic Technology and Petrochemistry. Slovak University of Technology in Bratislava, Faculty of Chemical Technology (1983) /. However, catalytic hydrogenation and nitrobenzene are of considerable industrial importance. to aniline at a temperature of 220-290 ° C on a copper catalyst (Cu on silica or silicate) or on a copper-nickel catalyst. However, the process is unsuitable for selective reduction as well as hydrogenation of more thermally labile aromatic nitro compounds and amines.

Furthermore, it is known to reduce aromatic nitro compounds by transition metal complexes, in particular platinum, palladium, rod, cobalt, copper and molybdenum / Izakovich E. N., Chidekel M.L .:

Usp. chimii 57, 758 (1988): Izakovich et al., Izv. AN USSR, ser. chim. 1982, p. 1517; Murthy N.V. and others: 0. Indian. Chem. Soc. 60, 524 (1983); Ito K .: Inorg. Chem. 22, 2872 (1983); Baker E. N. et al., J. Chem. Soc. A 1970, p. 400 /. However, their lack is the need for stoichiometric amounts of transition metal complexes. However, the reduction is interesting

3 molecular hydrogen, catalysed by cobalt pentacyanide, and in an aqueous and aqueous-alkaline medium, even at a temperature close to room temperature, it is formed from nitrobenzene azobenzene / Ogata M. et al., Science (Jap.). 1, 232 (1949); Kwiatek J. et al., J. Am. Chem. Soc. 84, 304 (1962); US Pat. No. 3,205,217], from nitrobenzene and o-nitroanisole, in turn, a mixture of azo and hydrazo compounds (Kwiatek J. et al. Adv. Chem.

Ser. 37. 201 (1963)] and a mixture of amine and azo compound at elevated hydrogen pressure. The more active and selective catalysts are platinum-palladium complexes. Under relatively mild conditions, nitrobenzene with a selectivity of 58% is hyarogenised to aniline (Hazarova NM et al., Izv. AH USSR series chim. 1981, p. 1500). Again, on sulfur-containing rhenium complexes, at 95 ° C and a hydrogen pressure of 0.1-4 MPa, nitrobenzene and nitrotoluene are hydrogenated to the corresponding aniline and toluidine (Belous VM et al., React. Kinet. Catal. Lett. 21, 371 (1982); ibid., 24, 271 (1984)] In recent years, palladium-platinum clusters such as Pd 2 (PPh) ₂ / Dorfman Ja have been studied.

A. and others: Izv. AH USSR ser. Chem. 1979, p. 2157; Pitman CU et al., J. Organometal. Chem. 178, 43 (1979)]. However, these are technically demanding catalysts and, moreover, require sufficiently refined raw materials. Similarly interesting, but less attractive to industry, is reduction with alkali metal borohydrides such as e.g. reduction of nitrobenzene to aniline by CuCl ₂ + + NaBH _{4 system} (Satoch T. et al., Chem. Ind. 1970, 1626). However, stoichiometric amounts of borohydrides are needed. Conversely, catalytic reduction with synthesis gas is also known, wherein the transition metal carbonyls exhibit catalytic activity, namely Rh _A (CO) ₁₂ and Co ₂ (CO) g in benzene or in a benzene-alcohol mixture at 120 ° C and synthesis gas pressure (CO). H ₂ = i: 1). Thus, the reduction of nitro compounds to amines

PiiNO ₂ + 2C0 + 2¾ -PhKHg + 2C0 ₂ proceeds with yield - 100 (δ) / Takesada.. and others: Ch.es. Soctapn 4_>,

2192 (1970); Murabashi et al., Ibid. 33, 78 (19).

Ruthenium Ru (CO) ₁₂ and Ru (CO) 2 (PPh 2) ₂ complexes in the presence of triethylammonium chloride catalyst are also effective catalysts (Cenini S. et al., Chem. Comrouns 1983,

-4 s. 1286). However, these processes require deeply refined synthesis gas and technically difficult to obtain catalysts. Disadvantages of hardly accessible noble metal catalysts also have the reduction of aromatic nitro compounds with alcohols and, in addition, low amine yields are achieved (Watanabe Y. et al.):

Chem. Lett. 1981, p. 1067). From a scientific point of view, understanding of the physiological processes increasingly requires attention to the fermentative reduction of aromatic compounds (Book R. and others: Mol. Pharmacol. 5, 487 (1969); Buhler D. P. et al. Biochem. Biophys. 103, 582 (1968)]. However, the catalytic reduction of aromatic nitro compounds by the action of carbon monoxide and water, where the hydrogen donor is water, is attractive.

PhNO 3 + 3 CO +

PhNH.

WHAT.

<2 · * ° ^u H 2 0 7 i 111 »112 s ^ ν» 2 ^-

Thus, the carbonyl complexes give birth to Rh 1 CO 3 and Rh 2 CO 3 at 150 ° C and a carbon monoxide pressure of 5-12 MPa by catalyzing the reduction of nitrobenzene to aniline in a yield of 85-95% (Iqbal A).

F .: Chem. techn. 2, 566 (1974)]. An optimum catalyst system appears to be Rhg (CO) 4-aminopolyyridine, which even makes it possible to reduce nitrobenzene at a temperature of 80 ° C and a carbon monoxide pressure of 0.1 MPa / Kaneda K. et al.: 3. M01. Catal. 12, 385 (1981)]. Other active catalysts include carbonyl

Rh ₆ (CO) ₁₆

0S2 (C0) ₁₂

H ₂ 0s (C 0) _1q

H ₄ O ₄ (CO) ₁₂ , Ir-j (CO) ₁₂

Pdj (CO) j (PPhj),, PdjQCOCOj CP CPP ¹¹ ^ ako ^and the platinum complex PtC CP CPPh ^ za in the presence of lewis acids such as ZnCl ^, SnCl ₂ , SnCl ^ / Watanabe Y. and others: Tetrahedron Lett. 24, 4121 (1983); Bull. Chem. Soc. Jap. 57, 2867 (1984)]. However, despite the obviously interesting reductive carbonylations catalysed by these catalysts, the disadvantage is their technical and economic complexity and the need for high purity carbon monoxide.

However, according to this invention, a process for preparing primary aromatic amines and / or diamines by carbonylation reduction of at least one aromatic nitro compound and / or dinitro compound with carbon monoxide-containing gas and water at a temperature of &lt; RTI ID = 0.0 &gt; Jcc &lt; / RTI &gt; / t, (

0 to 300 C, and 11 and the κ 0,] e 3 in MP 3 PART e - · <nt No 11 JPI s s, ₂ ekar - bonylačná reduction is catalyzed by a catalyst system consisting of sulfur and / or sulfur compound having a molecular weight of 34 up to 140 gmol ¹ in an amount of 0.1 to 20% by weight, with an alkali salt of carboxylic acid C.

6 masses. vanadium oxide and / or iron oxide in an amount of 0.01 to 20% by weight.

to C _of from 0.1 to 20% w of iron in an amount of addition or the oxygen in an amount of 0.1 to 7 wt.% and / or at least one compound of aliphatic tertiary amines having an alkyl number of 1 to 4, aromatic primary amine and morpholine in an amount of 1 to mass, all amounts being calculated on the weight of the aromatic nitro compound or nitro compounds.

The advantages of the process according to the invention are the technical simplicity, the technically easy availability of the new catalytic system, the possibility of using unrefined carbon monoxide gases. In addition, the presence of sulfur compounds in the carbon monoxide or in the carbon monoxide-containing gas is utilized as a component of the catalyst system, and thus the consumption of sulfur and sulfur compounds can be substantially reduced to effect reductive carbonylation of aromatic compounds. In addition, the method makes it possible to selectively reduce only some of the nitro groups of aromatic nitro compounds containing multiple nitro groups per molecule.

According to the invention, especially in the case of higher molecular aromatic compounds, they can be reductively carbonylated even if they contain more than two nitro groups per molecule. This is only a safety aspect of such reductive carbonylation (organic compounds, especially with a larger number of nitro groups in the molecule, are largely explosives).

The carbon monoxide-containing gas may be, on the one hand, unrefined carbon monoxide, synthesis gas, water gas, gas from coal gasification, methane gas, oil residue, etc., and such gases do not need to remove hydrogen sulfide, carbonyl sulfide and possibly other sulfur compounds. Nor is the presence of hydrogen, carbon dioxide, methane, nitrogen and other inert gases harmful. However, if the carbon monoxide content is low in such a gas, a lower reaction rate should be considered.

Elemental sulfur is most conveniently applied in powder form or dissolved in some of the starting materials, most preferably in the aromatic nitro compound. The most preferred sulfur compounds are hydrogen sulfide, carbonyl sulfide, carbon disulphide.

Thiols, dialkyl sulfides, dialkyl disulfides, thiophenes or homologues are also useful.

- 6-alkalildioulphides, thiophene q thiophane q their homologues *

The most suitable alkali salts of the weak carboxylic acids C 1 to C 8 are. sodium and potassium salts of acetic, propionic, butyric and isobutyric acids, other valeric, isovaleric, hydroxyvaleric, caproic and hydroxycaproic acids. Said salts can be applied in the form of hydrates, but also aqueous solutions or mixtures of aqueous solutions of sodium salts, as a by-product from organochemical processes. Such a suitable solution and the aqueous mixture of sodium salts of carboxylic acids and _of C · CL, being obtained as a by-product in the production of cyclohexanol and cyclohexanone by oxidation of cyclohexane.

Of the vanadium oxides, vanadium pentoxide is preferred, and iron oxide is iron oxide or hydroxide. Oxygen is particularly suitable in molecular form, but atomic as well as oxygen oligomers, especially ozone, are also useful. Oxygen in the form of peroxides, in particular hydrogen peroxide, is also less suitable but applicable to the process of the invention. Oxygen is preferably added as a controlled impurity in a carbon monoxide gas. Among the tertiary amines, trialkylamines, triarylamines, pyridine and its alkyl derivatives are suitable. Among the primary amines it is mainly aniline, toluidine and most often a part of recirculated primary amines and diamines. Then some secondary amines such as morpholine, pyrrole, diarylamines and dialkylamines.

Their presence as tertiary and primary amines in a reductive carbonylation environment is not necessary.

In order to increase the reaction rate of the reductive carbonylation of aromatic nitro compounds with carbon monoxide and water, it is advisable to add to the reaction medium either an organic, at least partially water-soluble aprotic solvent such as dioxane, acetone, dimethyl glycol ether, dimethylpolyglycol ether or the like. Preferably, at least a portion of the catalyst system is recirculated.

The process according to the invention can be carried out continuously, discontinuously or semi-continuously.

<- & a-l ereage ^ ^ »real-with-effect — it h´ô't ^ vyrráy 1 e u as-M-another

Example 1

Weigh 100 g of nitrobenzene, 200 g of methanol, 10 g of sodium acetate, 10 g of elemental sulfur powder, 13 g of iron oxide, 7.0 g of aniline, and 4 g of a 1 dm 2 stainless steel rotary autoclave. , 2 g vanadium pentoxide. After the autoclave is closed, the air is removed by blowing oxygen alone at atmospheric pressure (0.1 MPa) and then carbon monoxide (with 0.06% oxygen, 2.7% hydrogen and 1.35% v / v) is added. nitrogen) to a pressure of 14 MPa. Thereafter, the autoclave rotation is started and the heating is switched on. The desired reaction temperature is reached within 30 min and reductive carbonylation is continued from this point for 4 h. Both temperature and pressure are recorded at 10 min intervals. Thereafter, the rotation and tempering of the autoclave are stopped, the autoclave is cooled, the non-converted gas is vented, and the contents of the autoclave are quantitatively removed, weighed and analyzed.

In another experiment, working under otherwise similar conditions, only 10 g of water are added to the batch. j. 10% by weight. to nitrobenzene.

In all experiments, nitrobenzene conversion, selectivity to methyl-N-phenylcarbamate and aniline were determined, taking into account, of course, the added aniline. The results obtained are summarized in Table 1.

- 8 Table 1

Ŕeakčxxák warm; * Water addition / $ £ weight / nitro• benzene / conversion nitrobenzyl * ethoxybenzene /% / • Selectivity /% / n methyl-N- -phenyl- carbamate aniline 150 0.0 99.7 91.8 8.2 150 10,0 92.3 49.7 51.2 190 0.0 95.1 81.5 18.3 ~ · 190 10,0 95.0 43.8 55.4 90 0.0 8.8 100 0.0 90 10,0 8.4 67.0 33.0

Example 2

100 g of nitrobenzene, 200 g of methanol, 10 g of sodium acetate, 10 g of elemental sulfur powder are weighed into a rotating (180 rpm) stainless steel autoclave of 1 day volume,

1.2 g of vanadium pentoxide and various amounts of water. After closing the autoclave, the air is removed by blowing oxygen alone at atmospheric pressure. The carbon monoxide is then fed in with 0.39% by volume admixtures. oxygen, 1.7% v / v nitrogen and 2,44% vol. hydrogen to a pressure of 14 MPa. The rotation of the autoclave starts and the heating is switched on. A temperature of 150 ° C was reached during 30 rain _s and then the experiment was continued for 4 h. Temperature and pressure are recorded at 10 min _at intervals. After stopping the rotation and cooling the autoclave to room temperature, the product is removed, weighed and analyzed by liquid-gas chromatography. The results of the conversion of nitrobenzene and selectivity to methyl-K-phenylcarhamate and aniline in relation to the amount of water added were summarized in Table 2.

- 9 Table 2

-Additional water - /% <wt / nitrilebenzene / * conversion nitrobenzene Selectivity to: /% / /% / aniline ‘Methyl-N-phylcarbaraate 0.0 99.5 0 1oo 0.2 93.1 7.8 92.2 0.8 99.7 θ 2 91.7 3.0 99.0 16.0 84.0 5.0 99.3 65.6 10,0 99.1 50.3 49.5 50.0 100 98.5 1.5

Example 3

The procedure is similar to that of Example 2 except that the effect of the initial carbon monoxide pressure is investigated at a constant water content of 5% w / w. Thus, at an initial pressure of 3.5 MPa, the conversion of nitrobenzene reaches 48% and the selectivity to aniline is 38.3% and methyl-N-phenylcarbamate 61.4 ^l at 18 MPa, the conversion of nitrobenzene is 99.1%, the selectivity to aniline 39.1% and for methyl N-phenylcarbamate 60.6

Example 4

100 g of nitrobenzene, 100 g of water and optionally other additives, a catalyst system of 10 g of sulfur, 10 g of potassium acetate and 1.2 g of vanadium pentoxide are weighed into the autoclave specified in Examples 1 and 2. After the air has been removed by oxygen, carbon monoxide ε containing 0.4 vol. of oxygen and 2.02% v / v hydrogen at a pressure of 14 MPa, the reductive carbonylation is carried out at 150 ° C for 4 h. The data on the other ingredients and the results obtained are given in Table 3.

Table 3

Comes into water '•' t ·· <»·} * '» ·! · »·. * · Nitroben conversion \. zone. -i. /% / Aniline selectivity • /% / ^ amount. % / wt. / octyl polypropoxylate ⁺ ψψ oct and decyl polyglycol 1 31.0 97.8 2 32.0 97.7 emulsifier (mersolate) 2 49.3 98.0 eraulgátor (mersolate) 5 83.1 98.1 dodecybenzylamonium- bromide 2 34.1 98.1 acetone 50 97.0 98.9 dioxane 50 98.1 98.9

⁺ Polyaddition product of 15 moles of propylene oxide per mole of octanol; Polyaddition product of 20 moles of ethylene oxide per mole of oleyl alcohol.

»UlLlXLh

Weigh 100 g of 1-nitronaphthalene, 100 g of water, 5 g of carbon disulphide, g of sulfur, 5 g of sodium acetate, 4 g of a mixture of sodium carboxylic acid salts to C1-4. g of vanadium pentoxide and 60 g of dioxane.

After closing the autoclave and removing the air, carbon monoxide with an admixture of 0.4% by volume is passed. of oxygen and 2.02 ^c p vol. hydrogen to a pressure of 14 MPa. Reductive carbonylation is carried out at 150 ° C for 4 h. The nitronaphthalene conversion was 33.1% and the aminonaphthalene selectivity was 38.9%

- 11 Example 6. . The procedure is similar to that in Example 5, but instead of 100 g of nitronaithalene, 60 g of 1,4-dinitrobenzene are weighed. Its conversion reaches 99.6 selectivity to 1-nitro-4-aminobenzene 64% and to p-phenylenediamine 33.7% ·

Example 7

The procedure is analogous to Example 6, except that the carbon monoxide additionally contains 1.3% by volume. hydrogen sulphide; carbonylsulide and omit 2 g of elemental sulfur. The conversion of 1,4-dinitrobenzene is 99.3%, the selectivity to 1-nitro-4-aminobenzene is 39.8 and to the p-phenylenediamine is 59.8%.

Example 8

The procedure is similar to that in Example 6, except that 100 g of 1-nitro-3-chlorobenzene are weighed in place of 100 g of nitronaithalene. Conversion reaches 96.8x and s-selectivity to 1-amino-3-chlorobenzene reaches 84.6

Example 9

The procedure is analogous to Example 6, except that 100 g of 4-nitrotoluene are weighed in place of 100 g of nitronaithalene. The conversion reached 99.7% and the selectivity to 4-aminotoluene 98.9

Example 10

The procedure is analogous to Example 7 except that 2.5 g is used instead of carbon 5. The 1,4-dinitrobenzene conversion reached 98.7% and the selectivity to 1-nitro-4-aminobenzene reached 42.1% and to p-phenylenediamines. 57.3%> · dog width

Example 11

100 g of nitrobenzene, 200 g of methanol, g of water, 10 g of powdered sulfur, 1,2 g of vanadium pentoxide,

13.2 g of iron oxide, 4.2 g of morpholine and 15.9 g of aniline.

After closing the autoclave and removing the air with nitrogen, carbon monoxide containing 1.4% by volume is fed to a pressure of 14 MPa. oxygen and 1.5% v / v nitrogen. The temperature of the reductive carbonylation is 160 ° C and the reaction time is 5 h. Nitrobenzene conversion reached 97.6%, aniline selectivity 57.8% and methyl N-phenylcarbamate 38.5%.

Example 12

Weigh 100 g of 4-nitro toluene, 150 g of water and 8 g of a mixture of sodium carboxylic acids C2-C4, obtained from the so-called &quot; C2-C4 &quot; alkaline waters from the oxidation of cyclohexane to cyclohexanol and cyclohexanone. Furthermore, 1.0 g of vanadium pentoxide and 5 g of dimethylsulfide. After closing the autoclave, unrefined carbon monoxide with admixtures of 0.87 vol. of carbonyl sulfide, 0.5 vol. oxygen, 2.1 vol.

hydrogen, 2.4% v / v nitrogen and 0,2% vol. of carbon dioxide up to 14 MPa. Thereafter, the contents of the autoclave are heated to 175 ° C with constant rotation and maintained at this temperature for 3 h. The conversion of 4-nitrotoluene is 100% and the selectivity to 1-methyl-4-aminobenzene 98%.

Example 13

The procedure is analogous to Example 12 except that 5 g of diethyl disulfide is used instead of 5 g of dimethyl sulfide. Complete conversion of 4-nitrotoluene and selectivity to 1-methyl-4-aminobenzene of 97.5% are also achieved.

Example 14

The procedure is similar to Example 12, only instead of 8 g of a mixture of sodium salts of carboxylic acids C ₂ is applied to a mixture of 8 g of potassium salts of carboxylic acids, C ₂ to C ^, consisting of 24% RH. potassium acetate, 5.6% rel. of potassium propionate, 38% rel. potassium butyrate, 31% rel. potassium valerate and 2.4% rel. potassium caproate. Complete conversion of 4-nitronaphthalene and selectivity to 1-methyl-4-aminobenzene of 98% is also achieved.

Example 15

50 g of 1-nitrofluorene, 50 g of dioxane, 60 g of distilled water, 0.3 g of dodecylpolyethylene glycol ether, 5 g of triethylamine, 3 g of potassium valerate are weighed into a rotary autoclave (240 rpm) of 0.5 dm @ 2. g of vanadium pentoxide, g of morpholine and 2.5 g of hydrogen sulphide after autoclaving.

Carbon monoxide with an admixture of 0.3% vol. of carbonyl sulfide, 0.4 vol. oxygen, 1.8 h vol. nitrogen,

1,3% vol. hydrogen and 0.2 vol. carbon dioxide. Reductive carbonylation is carried out at 165 ° C for 4 h. The conversion of 1-nitrophenyl luorene reaches 96.3 ^? and selectivity to 1-aminofluorene 84%.

Example 16

50 g of 1-nitro-2-methyl-4-fluorobenzene, g of dimethyl glycol ether, 100 g of water, 5 g of potassium hydroxyvalerate, 2 g of triisobutylamine, 1 g of toluidine are weighed into a 0.5 dm &lt; 3 &gt; 1 g of vanadium pentoxide and, after closing the autoclave, 2 g of hydrogen sulphide and carbon monoxide, as specified in Example 15, are passed to a pressure of 12 MPa. The reaction was carried out at 100 ° C for 8 h. The conversion of 1-nitro-2-methyl-1-fluorobenzene is 96% and the selectivity to 1-amino-2-methyl-4-fluorobenzene is 83%.

Example 17

The procedure is analogous to Example 16 except that 4-nitrotoluene is used as the aromatic nitro compound and 4 g of toluidine is used instead of 1 g of toluidine. The conversion of 4-nitrotoluene is 95-100% and the selectivity to p-toluidine is 96-99%.

In a further experiment, already recirculated p-toluidine containing also recirculated triisobutylamine was used, with a conversion of 4-nitrotoluene of 96-100% and a selectivity of 96-99 h being also achieved.

Claims (7)

Process for the preparation of primary aromatic amines and / or diamines by carbonylation reduction of at least one aromatic nitro compound and / or dinitro compound with carbon monoxide-containing gas and water at a temperature of 80 to 300 ° C and a pressure of 0.1 to 300 MPa, characterized in that the carbonylation catalyzed reduction of a catalyst system consisting of sulfur and / or sulfur compound of molecular weight 34-140 g mol ^- ^ ^- from 0.1 to 20% by hmo'fe? ^ an alkali salt of a carboxylic acid and from 0.1 to 20% by weight ^ ⁷ with an amount of 0.01 to 20% by weight of vanadium oxide and / or iron oxide, optionally with oxygen in an amount of 0.1 to 7% by weight of PC and / or at least one compound of aliphatic tertiary amines having 1 to 4 aromatic carbons % of primary amine and morpholine in an amount of 1 to 10% by weight, all amounts being calculated on the weight of the aromatic nitro compound or nitro compounds. A process according to claim 1, wherein the sulfur compound is at least one of hydrogen sulfide, carbonyl sulfide, carbon disulfide, dimethyl sulfide, diethyl sulfide, dimethyl disulfide and diethyl disulfide. Preparation process according to claims 1 and 2, characterized in that the alkali salt is a sodium and / or potassium salt, preferably sodium acetate and / or potassium acetate, wherein the alkali salt can be formed from the raw materials in situ. Method according to one of Claims 1 to 3, characterized in that the iron oxide is iron oxide, preferably iron oxide and / or iron (III) oxide. Preparation process according to claims 1 to 4, characterized in that the oxygen is added to the reaction medium with carbon monoxide and / or in particular, preferably in the form of air admixtures. Process according to claims 1 to 5, characterized in that the primary aromatic amine is a recirculated primary aromatic amine, preferably aniline or diamine, preferably phenylenediamine. Process according to Claims 1 to 6, characterized in that a phase transfer catalyst or an aprotic solvent, preferably acetone or a dialkyl glycol ether, is added to the reaction medium.