Process for producing aromatic amines

Abstract: A process for producing an aromatic amine under moderate conditions is provided where a catalyst higher in activity than conventional catalysts is used. Reduction of an aromatic nitro compound under a CO/H₂O system is conducted using a rhodium compound catalyst in the presence of an aqueous alkali solution such as aqueous sodium hydroxide solution. Alternatively, an aromatic nitro compound is reduced under a CO/H₂O system using a rhodium compound or a ruthenium compound catalyst in the presence of the aqueous alkali solution and additionally at least one compound of amine compounds, diamine compounds, phosphine compounds, phosphite compounds, and diphosphine compounds.

Description: The present invention relates to a process for producing aromatic amines by reduction of aromatic nitro compounds. Aromatic amines including aniline are industrially important compounds as medicines, agricultural chemicals, dyes, pigments, pharmaceuticals and intermediates thereof. It is known to produce aromatic amines by reduction of aromatic nitro compounds under a CO/H₂O system in the presence of a catalyst. U.S. 3,293,295 discloses to carry out the reaction in an alkaline medium without any other catalyst. U.S. Patent No. 3,944,615 discloses to carry out the reaction in a solvent such as pyridine or N-methylpyridine using Rh₆(CO)₁₆ or Rh₂O₃ as a catalyst under high temperature and high pressure e.g. 50 - 150°C and CO 50 - 120 atm. European Patent Laid-Open Application No. 97592 discloses to carry out the reaction in a solvent such as ethanol using Rh₆(CO)₁₆ as a catalyst with addition of 3,4,5,6,7,8-hexamethylphenanthroline under high temperature and high pressure e.g. 165°C and CO 30 atm. As a reaction at high temperature (e.g., 80°C) and under atmospheric pressure, "Journal of Molecular Catalysis", Vol. 12, No. 385 (1981) discloses to carry out the reaction in a solvent of 2-ethoxyethanol-water using Rh₆(CO)₁₆ as a catalyst with addition of various amines. As a reaction under room temperature and atmospheric pressure, "Tetrahedron Letters", Vol. 21, No. 27, 2603-2604 (1980) discloses to carry out the reaction in a mixed solution of 2-methoxyethanol-benzene-aqueous sodium hydroxide solution using a catalyst Ru₃(CO)₁₂ and a phase-transfer catalyst such as (PhCH₂)Et₃N⁺Cl⁻. However, according to these methods, since catalytic activities are low and the reduction is difficult to proceed under moderate conditions, it is necessary to raise reaction temperature or enhance CO pressure. Furthermore, there is a problem in selectivity of reaction products under conditions of high temperature and high pressure. Under the moderate conditions of room temperature and atmospheric pressure, since catalytic activity is low, desired compounds are hardly obtained in high yields unless catalyst concentration is increased or reaction is conducted for a long time even with addition of phase-transfer catalysts. SUMMARY OF THE INVENTION An object of the present invention is to provide a process for producing an aromatic amine by reduction of an aromatic nitro compound under a CO/H₂O system and moderate conditions using a catalyst higher in activity than conventional catalysts. Another object of the present invention is to provide a process for producing an aromatic amine by catalytic reduction of aromatic nitro compounds using CO and water in high yield and with remarkably high selectivity. That is, the present invention provides a process for producing an aromatic amine by reducing an aromatic nitro compound under a CO/H₂O system using a catalyst comprising a rhodium compound, characterized by carrying out the reduction in the presence of an aqueous alkali solution. The present invention further provides a process for producing an aromatic amine by reducing an aromatic nitro compound under a CO/H₂O system using a catalyst comprising a rhodium compound or a ruthenium compound, characterized by carrying out the reduction with addition of at least one compound selected from the group consisting of amine compounds, diamine compounds, phosphine compounds, phosphite compounds and diphosphine compounds in the presence of an aqueous alkali solution. DESCRIPTION OF THE INVENTION The present invention will be explained in detail. It is presumed that the reaction proceeds according to the following formula when, for example, nitrobenzene is used as aromatic nitro compounds. PhNO₂ + 3CO + H₂O → PhNH₂ + 3CO₂ This reaction is characterized in that CO/H₂O is used as a hydrogen source. The aromatic nitro compound used in the present invention is a compound having at least one nitro group in an aromatic ring. The aromatic ring includes heterocyclic aromatic rings such as pyridine and quinoline in addition to hydrocarbon aromatic rings such as benzene, naphthalene and anthracene. Furthermore, these aromatic nitro compounds may have substituents such as an alkyl group, halogen, an amino group, a hydroxyl group, a carbonyl group, an alkoxy group, a cyano group and a sulfone group in addition to a nitro group. As aromatic nitro compounds normally used, mention may be made of, for example, nitrobenzene, o-nitrotoluene, p-nitrotoluene, 2-nitro-p-xylene, o-chloronitrobenzene, p-chloronitrobenzene, p-cyanonitrobenzene, o-nitroaniline, o-dinitrobenzene, p-nitroaniline, m-dinitrobenzene, 2,4-dinitrotoluene, o-nitrophenol, p-nitrophenol, o-nitroanisole, p-nitroanisole, α-nitronaphthalene, β-nitronaphthalene, 1-nitroanthraquinone, 2-nitroanthraquinone, 1,5-dinitroanthraquinone, 1,8-dinitroanthraquinone, 4-nitroimidazole, o-nitrobenzonitrile, p-nitrobenzonitrile, o-nitrobenzenesulfonic acid, p-nitrobenzenesulfonic acid, o-nitrobenzenesulfonamide, and p-nitrobenzenesulfonamide. The catalyst used in the present invention is a rhodium compound or a ruthenium compound and is preferably a complex having carbonyl ligand or a compound capable of easily forming a carbonyl complex under reaction conditions. As examples of this catalyst, mention may be made of Rh(CO)₂(acac), [RhCl(COD)]₂, RhH(CO)(PPh₃)₂, Rh₄(CO)₁₂, Rh₆(CO)₁₆, RhCl(CO)(PPh₃)₂, Rh₂(OAc)₄, Rh(acac)₃, RhCl(PPh₃)₃, RhH(PPh₃)₃, RuH₂(PPh₃)₄, RuCl₂(PPh₃)₄, RuCl₂(CO)₂(PPh₃)₂, Ru₃(CO)₁₂, H₄Ru₄(CO)₁₂, Ru(acac)₃, Ru(CF₃COCH₂COCF₃)₃, RuH(OAc)(PPh₃)₃, RuHCl(PPh₃)₃, and [RuCl₂(COD)]n. Among them, carbonyl complexes of rhodium or ruthenium are especially preferred. In the present invention, excellent catalytic activity is exhibited by using an aqueous alkali solution. The aqueous alkali solution may be an aqueous solution of any of LiOH, NaOH, KOH, RbOH, and CsOH. Usually, an aqueous solution of NaOH is used. Alkali concentration is usually 0.1 - 10N, preferably 3 - 7N. Reaction temperature is usually 0 - 200°C, especially preferably 20 - 150°C and the reaction proceeds efficiently even at about room temperature (about 25°C). The reaction proceeds without a solvent, but use of a solvent is more preferred. The solvent includes, for example, alcohols such as 2-methoxyethanol, 2-propanol, methanol, and ethanol, hydrocarbons such as benzene, toluene, and xylene and glymes such as diethylene glycol dimethyl ether. Pressure of CO used in the present invention is usually 1 - 100 atm or higher (1 atm = 1,01325 x 10⁵ Pa). The reaction of the present invention efficiently proceeds even under atmospheric pressure. In the present invention, higher catalytic activity is exhibited by using catalyst systems comprising a rhodium compound or a ruthenium compound to which is added at least one compound selected from amine compounds, diamine compounds, phosphine compounds, phosphite compounds and diphosphine compounds. The amine compounds used in the present invention include primary amines, secondary amines and tertiary amines. Examples thereof are imidazoles such as imidazole, N-methylimidazole, 2-methylimidazole, benzimidazole, 2-methylbenzimidazole, and N-methylbenzimidazole, pyridines such as 4,4-dimethylaminopyridine, pyridine, α-picoline, β-picoline, γ-picoline, 4-cyanopyridine, 2-cyanopyridine and 2-hydroxypyridine, pyrrolidine, piperidine, piperazine, pyrrole, triethylamine, trinormalpropylamine, trinormalbutylamine, N,N-dimethylbenzylamine, diisopropylamine, and 1-aminoanthraquinone. Among them, preferred are 2-methylbenzimidazole, triethylamine, trinormalbutylamine, 2-hydroxypyridine and N,N-dimethylbenzylamine. The diamines used in the present invention are chelate amines which have two nitrogen atoms at 2,2′; 1,2 (including 2,3 and 9,10); 1,3; 1,4; 1,5; 1,8 or 1,10 positions and examples thereof are ethylenediamine, N,N,N′,N′-tetramethylethylenediamine, N,N,N′,N′-tetramethyl-1,3-propanediamine, N,N,N′,N′-tetramethyl-1,4-butanediamine, o-phenylenediamine, 9,10-diaminophenanthrene, 2,3-naphthalenediamine, 1,8-naphthalenediamine, 1,8-bis(dimethylamino)naphthalene, 2-aminopyridine, α,α′-bipyridyl, 1,10-phenanthroline, and 3,4,7,8-tetramethyl-1,10-phenanthroline. Among them, preferred are aromatic diamines such as 9,10-diaminophenanthrene, o-phenylenediamine, 1,8-bis (dimethylamino)naphthalene and N,N,N′,N′-teteramethyl-1,4-butanediamine. The above amines or diamines are added in an amount of usually 0.01 - 200 mols, more preferably 0.01 - 20 mols per one mol of a catalyst metal atom. The phosphines used in the present invention are represented by the formula: PR¹R²R³ (wherein R¹, R² and R³ each represents an alkyl group of 1 - 8 carbon atoms, a cycloalkyl group of 6 - 8 carbon atoms or a phenyl group, with a proviso that all of R¹, R² and R³ are not simultaneously phenyl groups). Examples are trialkylphosphines such as trimethylphosphine, triethylphosphine, tri-n-propylphosphine, triisopropylphosphine, tri-n-butylphosphine, tri-tert-butylphosphine and tri-cyclohexylphosphine, tertiary phosphines having phenyl group such as diphenylethylphosphine, diphenylmethylphosphine, diethylphenylphosphine and dimethylphenylphosphine, and tertiary phosphines having different alkyl groups or cycloalkyl groups such as ethyl-di-tert-butylphosphine. Preferred are diethylphenylphosphine and triethylphosphine. The phosphites used in the present invention are represented by the formula: P(OR)₃ (wherein R represents an alkyl group of 1 - 5 carbon atoms or a phenyl group) and examples thereof are compounds where a hydrocarbon group and a phosphorus atom are bonded through an oxygen atom such as trimethylphosphite, triethylphosphite and triphenylphosphite. The phosphine or phosphite are added in an amount of 0.01 - 100 mols, more preferably 0.01 - 20 mols per one mol of a catalyst metal atom. The diphosphines used in the present invention are chelate phosphines having two phosphorus atoms which are represented by the formula: R₂P(CH₂)nPR₂ (wherein R represents an alkyl group of 1 - 8 carbon atoms, a cycloalkyl group of 6 - 8 carbon atoms, a phenyl group or a tolyl group and n denotes an integer of 1 - 6) such as Ph₂PCH₂PPh₂, Ph₂P(CH₂)₂PPh₂, Ph₂P(CH₂)₃PPh₂, Ph₂P(CH₂)₄PPh₂, Ph₂P(CH₂)₅PPh₂, nBu₂P(CH₂)₂PnBu₂, Et₂P(CH₂)₂PEt₂, Me₂PCH₂PMe₂, Me₂P(CH₂)₂PMe₂, (C₆H₁₁)₂P(CH₂)₂P(C₆H₁₁)₂, and (p-CH₃C₆H₄)₂P(CH₂)₂P(p-CH₃C₆H₄)₂. Among them, preferred are Ph₂PCH₂PPh₂, Ph₂P(CH₂)₂PPh₂ and Ph₂P(CH₂)₅PPh₂. The diphosphine is added in an amount of usually 0.01 - 10 mols, preferably 0.01 - 4 mols per one mol of a catalyst metal atom. In the present invention, when a rhodium compound is used as a catalyst, sufficiently superior catalytic activity is able to be exhibited with use of only an aqueous alkali solution and without addition of the above-mentioned amine compounds, diamine compounds, phosphine compounds, phosphite compounds and diphosphine compounds. As explained in detail above, according to the present invention, catalytic activity is high and even under very moderate conditions such as room temperature and atmospheric pressure, catalytic activity conspicuously higher than that in conventional techniques and besides the objective aromatic amines are obtained selectively and in high yields. Thus, the present invention is remarkably economical. The following nonlimiting examples will further explain the invention. Examples 1 - 4 In Schlenk tubes of 50 ml each in capacity were introduced catalysts shown in Table 1 (0.02 mmol) (0.01 mmol in Example 4), 2-methoxyethanol (15 ml), a 5N aqueous sodium hydroxide solution (5 ml) and nitrobenzene (5 mmol) respectively and gas bags each of carbon monoxide (1 atm) was equipped at the ends of the Schlenk tubes, followed by stirring at 25°C for 3 hours to allow the reactions proceed. The reaction products were analyzed by gas chromatography and identification was carried out by comparison of retention time in gas chromatogram and by GC - MS. The same analytical method was employed in the following examples and comparative examples. As a result of the analysis, the reaction products comprised only aniline and no by-products were present. The results are shown in Table 1. The following total turnover number (TN) was used as an indicator for catalytic activity. Total turnover number (TN) = amount of aromatic amine produced (mmol)/amount of a catalyst metal atom (mg - atom). Example 5 Rh₄(CO)₁₂ (0.01 mmol), diethylene glycol dimethyl ether (30 ml), a 5N aqueous sodium hydroxide solution (10 ml) and 1-nitroanthraquinone (10.6 mmol) were introduced in a three-necked flask of 200 ml capacity and two gas bags of carbon monoxide (1 atm) were equipped at the end of the tube by a three-way cock and the content was stirred at 25°C for 3 hours to allow the reaction proceed. The reaction product comprised only 1-aminoanthraquinone and no by-products were present. Results of the reaction are shown in Table 1. Comparative Example 1 Reaction was carried out in the same manner as in Example 1 except that an aqueous alkali solution was not used and Rh₄(CO)₁₂(0.02 mmol), 2-methoxyethanol (5 ml) and water (1 ml) were used. The reaction product comprised only aniline and no by-products were present. Results are shown in Table 1. Catalyst TN Example 1 Rh₄(CO)₁₂ 23 Example 2 Rh(CO)₂(acac) 37 Example 3 [RhCl(COD)]₂ 30 Example 4 Rh₆(CO)₁₆ 81 Example 5 Rh₄(CO)₁₂ 93 Comparative Example 1 Rh₄(CO)₁₂ 1 or less Examples 6 - 16 In Schlenk tubes of 50 ml each in capacity were introduced Rh(CO)₂(acac) (0.02 mmol in Example 6 and 0.005 mmol in other Examples), diethylene glycol dimethyl ether (7.5 ml), a 5N aqueous sodium hydroxide solution (2.5 ml), phosphine or phosphite shown in Table 2 in an iquimolar amount with the catalyst (0.005 mmol) and nitrobenzene (5 mmol) and a gas bag each of carbon monoxide (1 atm) was equipped at the ends of the tubes and reactions were allowed to proceed for 2 hours at 25°C with stirring. The reaction products comprised only aniline and no other by-products were present. The results of the reaction are shown in Table 2. Phosphine or phosphite TN Example 6 - 5 Example 7 PEtPh₂ 14 Example 8 PEt₂Ph 116 Example 9 PEt₃ 241 Example 10 PMe₃ 91 Example 11 PCy₃ 35 Example 12 P(i-C₃H₇)₃ 27 Example 13 P(OEt)₃ 21 Example 14 P(OPh)₃ 39 Example 15 P(t-Bu)₃ 15 Example 16 PEt(t-Bu)₂ 28 Example 17 PEt₃ 22 Example 17 Reaction was carried out in the same manner as in Example 7 except that [RuCl₂(COD)]n (manufactured by Kanto Chemical Co.) (0.01 mmol Ru), triethylphosphine (0.01 mmol), 2-methoxyethanol (15 ml) and a 5N aqueous sodium hydroxide solution (5 ml) were used. The reaction product comprised only aniline and no by-products were present. Results of the reaction are shown in Table 2. Examples 18 - 21 Reactions were carried out in the same manner as in Example 7 except that phosphine was used in the amounts as shown in Table 3. The reaction products comprised only aniline and no by-products were present. Results of the reactions are shown in Table 3. Phosphine Molar ratio TN Example 18 PEt₂Ph 2 75 Example 19 PEt₃ 2 154 Example 20 PEt₃ 5 140 Example 21 PEt₃ 10 102 Examples 22 - 27 Reactions were carried out under the same conditions as in Example 7 except that amount of diethylene glycol dimethyl ether was changed to 15 ml and amount of a 5N aqueous sodium hydroxide solution was changed to 5 ml and phosphines or nitro compounds (5 mmol) as shown in Table 4 were used and reaction temperatures and reaction times as shown in Table 4 were employed. The reaction products comprised only the desired compound and no by-products were present. Results of the reaction are shown in Table 4. Nitro compound Phosphine Reaction temperature (°C) Reaction time (Hr) TN Yield (%) Example 22 Nitrobenzene PEtPh₂ 50 2 52 5 Example 23 Nitrobenzene PEt₂Ph 50 2 609 59 Example 24 Nitrobenzene PEt₃ 50 2.5 758 70 Example 25 Nitrobenzene PEt₃ 25 12 237 95 Example 26 p-Nitrotoluene PEt₃ 25 12 192 77 Example 27 p-Chloronitrobenzene PEt₃ 25 12 >250 100 Example 28 - 36 Reactions were carried out under the same conditions as in Example 1 except that catalysts (0.02 mmol with the exception of 0.005 in Example 29 and 0.01 mmol in Example 36) and diphosphines as shown in Table 5 were used. In Example 29, the reaction was carried out using diethylene glycol dimethyl ether (7.5 ml) and a 5N aqueous sodium hydroxide solution (2.5 ml). Reaction products comprised only aniline and no by-products were present. Results of the reaction are shown in Table 5. Comparative Examples 2 - 4 Reactions were carried out under the same conditions as in Example 1 except that catalysts (0.02 mmol) and phosphines as shown in Table 5 were used. Phosphine was not added in Comparative Example 2. Reaction products comprised only aniline and no by-products were present. Results of the reactions are shown in Table 5. Examples 37 - 46 In Schlenk tubes of 50 ml each capacity were introduced catalysts shown in Table 6 (0.02 mmol), 2-methoxyethanol (15 ml), a 5N aqueous sodium hydroxide solution (5 ml), 1,2-bis(diphenylphosphino)ethane in the amount as shown in Table 6 and nitro compounds as shown in Table 6 (5 mmol) and gas bag each of carbon monoxide (1 atm) was equipped at the ends of the Schlenk tubes and reactions were allowed to proceed by stirring at 25°C for a reaction time as shown in Table 6. The reaction products comprised only the objective compound and no by-products were present. Results of the reaction are shown in Table 6. Examples 47 - 66 Reactions were carried out under the same conditions as in Example 2 except that amine or diamine as shown in Table 7 was used. In Example 62, amount of Rh(CO)₂(acac) was 0.01 mmol. Reaction products comprised only aniline and no by-products were present. Results of the reaction are shown in Table 7. Amine or diamine Molar ratio TN Example 47 N-methylimidazole 3 52 Example 48 Pyridine 3 61 Example 49 Pyrrolidine 3 54 Example 50 Triethylamine 3 66 Example 51 2-Aminopyridine 1.5 60 Example 52 Ethylenediamine 1.5 52 Example 53 N,N,N',N'-tetramethylethylenediamine 1.5 68 Example 54 N,N,N',N'-tetramethyl-1,3-propanediamine 1.5 62 Example 55 o-Phenylenediamine 1.5 155 Example 56 2,3-Naphthalenediamine 1.5 99 Example 57 9,10-Diaminophenanthrene 1.0 118 Example 58 " Example 59 " 4.0 98 Example 60 " 1.5 241 Example 61 " 1.5 72 Example 62 " 1.5 172 Example 63 1,8-Naphthalenediamine 1.5 68 Example 64 α,α'-bipyridyl 1.5 60 Example 65 3,4,7,8-tetramethyl-1,10-phenanthroline 1.5 57 Example 66 N,N,N',N'-tetramethyl-1,4-butanediamine 1.5 60 Examples 67 - 72 Reactions were carried out under the same conditions as in Example 6 except that amine or diamine shown in Table 8 and Rh₆(CO)₁₆ (0.001 mmol) were used. Reaction products comprised only aniline and no by-products were present. Results of the reaction are shown in Table 8. Amine or diamine Molar ratio TN Example 67 triethylamine 3 47 Example 68 trinormalpropylamine 3 43 Example 69 diisopropylamine 3 28 Example 70 4-cyanopyridine 3 30 Example 71 piperadine 3 30 Example 72 N,N,N′,N′-tetramethyl-1,4-butanediamine 1 27 Examples 73 - 92 Reactions were carried out for 1 hour under the same conditions as in Example 4 except that amine or diamine shown in Table 9, p-nitrotoluene or p-nitroanisole (5 mmol) as aromatic nitro compounds were used in the presence of Rh₆(CO)₁₆ (0.001 mmol). Reaction products comprised only p-toluidine from p-nitrotoluene and p-anisidine from p-nitroanisole and no by-products were present. Results of the reaction are shown in Table 9. Examples 93 - 106 Reactions were carried out under the same conditions as in Example 1 except that amine or diamine as shown in Table 10 and nitrobenzene (10 mmol) and Ru₃(CO)₁₂ (0.02 mmol) were used. Reaction products comprised only aniline and no by-products were present. Results of the reaction are shown in Table 10. Examples 107 - 114 and Comparative Example 5 Reactions were carried out in the same manner as in Example 58 except that solvents and bases as shown in Table 11 were used. Reaction products comprised only aniline and no by-products were present. Results of the reaction are shown in Table 11. Amine or diamine Molar ratio TN Example 93 N,N,N′,N′-tetramethylethylenediamine 1.5 26 Example 94 N,N,N′,N′-tetramethyl-1,3-propanediamine 1.5 30 Example 95 N,N,N′,N′-tetramethyl-1,4-butanediamine 1.5 28 Example 96 2,3-Naphthalenediamine 1.5 26 Example 97 9,10-Diaminophenanthrene 1.5 31 Example 98 3,4,7,8-Tetramethyl-1,10-phenanthroline 1.5 29 Example 99 Imidazole 3 27 Example 100 N-methylimidazole 3 27 Example 101 2-Methylimidazole 3 26 Example 102 Benzimidazole 3 26 Example 103 2-Methylbenzimidazole 3 37 Example 104 Pyridine 3 37 Example 105 4,4-Dimethylaminopyridine 3 26 Example 106 Triethylamine 3 39 Examples 115 - 120 Reactions were carried out under the same conditions as in Example 1 except that Rh₄(CO)₁₂ as shown in Table 12 and 9,10-diaminophenanthrene were used. Reaction products comprised only aniline and no by-products were present. Results of the reaction are shown in Table 12. Comparative Examples 6 - 8 Reactions were carried out under the same conditions as in Example 1 except that water (5 ml) in place of the 5N aqueous sodium hydroxide solution, N,N,N′,N′-tetramethylethylenediamine and Rh₄(CO)₁₂ of the concentration as shown in Table 12 were used. In comparative Example 7, reaction temperature was 70°C and in Comparative Example 8, reaction temperature was 70°C and CO pressure was 50 kg/cm². Reaction products comprised only aniline and no by-products were present. Results of the reaction are shown in Table 12. Examples 121 - 125 Reactions were carried out under the same conditions as in Example 5 except that amines as shown in Table 13 were used. Reaction products comprised only 1-amino-anthraquinone and no by-products were present. Results of the reaction are shown in Table 13. Amine Molar ratio TN Example 121 Triethylamine 3 139 Example 122 Triethylamine 10 114 Example 123 4,4′-Dimethylaminopyridine 3 132 Example 124 1-Aminoanthraquinone 3 117 Example 125 9,10-Diaminophenanthrene 1.5 105 Examples 126 - 146 In Schlenk tubes of 50 ml each were charged catalysts shown in Table 14, amines or diamines shown in Table 14, 2-methoxyethanol (15 ml), a 5N aqueous sodium hydroxide solution (5 ml), and nitro compounds shown in Table 14 (5 mmol except 5.3 mmol in Examples 145 and 146) and a gas bag each of carbon monoxide (1 atm) was equipped at the ends of the Schlenk tubes and reactions were allowed to proceed at 25°C for periods as shown in Table 14 with stirring. Reaction products comprised only the desired product and no by-products were present. Results of reaction are shown in Table 14.

Claims: A process for producing an aromatic amine which comprises reducing an aromatic nitro compound under a CO/H₂O system in the presence of a catalyst comprising a rhodium compound wherein the reduction is carried out in the presence of an aqueous solution of alkali selected from LiOH, NaOH, KOH, RbOH, and CsOH. A process for producing an aromatic amine which comprises reducing an aromatic nitro compound under a CO/H₂O system in the presence of a catalyst comprising a rhodium compound or a ruthenium compound wherein the reduction is carried out in the presence of an aqueous solution of alkali selected from LiOH, NaOH, KOH, RbOH, and CsOH with addition of at least one compound selected from the group consisting of amine compounds, diamine compounds, phosphine compounds, phosphite compounds and diphosphine compounds. A process according to claim 1 or 2, wherein the rhodium compound is Rh(CO)₂(acac), [RhCl(COD)]₂, Rh₄(CO)₁₂ or Rh₆(CO)₁₆. A process according to claim 2, wherein the ruthenium compound is Ru₃(CO)₁₂ or [RuCl₂(COD)]n. A process according to claim 2, wherein the amine compound is a primary amine, a secondary amine or a tertiary amine. A process according to claim 5, wherein the primary amine is 1-aminoanthraquinone. A process according to claim 5, wherein the secondary amine is imidazole, 2-methylimidazole, benzimidazole, pyrrolidine, diisopropylamine or pyrrole. A process according to claim 5, wherein the tertiary amine is triethylamine, trinormalpropylamine, trinormalbutylamine, N,N-dimethylbenzylamine, N-methylimidazole, 4,4-dimethylaminopyridine, pyridine, 4-cyanopyridine, α-picoline, β-picoline, γ-picoline or 2-hydroxypyridine. A process according to claim 5, wherein the amine compound is 2-methylbenzimidazole, triethylamine, trinormalbutylamine, 2-hydroxypiridine or N,N-dimethylbenzylamine. A process according to claim 2, wherein the diamine compound is a chelate amine which has two nitrogen atoms at 2,2′, 1,2, 1,3, 1,4, 1,5, 1,8, or 1,10 positions. A process according to claim 10, wherein the diamine compound is ethylenediamine, N,N,N′,N′-tetramethylethylenediamine, N,N,N′,N′-tetramethyl-1,3-propanediamine, N,N,N′,N′-tetramethyl-1,4-butanediamine, 1,8-bis(dimethylamino)naphthalene, o-phenylenediamine, 9,10-diaminophenanthrene, 2,3-naphthalenediamine, 1,8-naphthalenediamine, 2-aminopyridine, α,α′-bipyridyl or 3,4,7,8-tetramethyl-1,10-phenanthroline. A process according to claim 11, wherein the diamine compound is 9,10-diaminophenanthrene, o-phenylenediamine, 1,8-bis(dimethylamino)naphthalene or N,N,N′,N′-tetramethyl-1,4-butanediamine. A process according to claim 2, wherein the phosphine compound is represented by the formula: PR¹R²R³ wherein R¹, R² and R³ each represents an alkyl group of 1 - 8 carbon atoms, a cycloalkyl group of 6 - 8 carbon atoms or a phenyl group with a proviso that all of R¹, R² and R ³ are not simultaneously phenyl groups. A process according to claim 13, wherein the phosphine compound is trimethylphosphine, triethylphosphine, triisopropylphosphine, tri-tert-butylphosphine, tricyclohexylphosphine, diphenylethylphosphine, diethylphenylphosphine or ethyl-di-tert-butylphosphine. A process according to claim 14, wherein the phosphine compound is diethylphenylphosphine or triethylphosphine. A process according to claim 2, wherein the phosphite compound is represented by the formula: P(OR)₃ wherein R represents an alkyl group of 1 - 5 carbon atoms or a phenyl group. A process according to claim 16, wherein the phosphite compound is triethylphosphite or triphenylphosphite. A process according to claim 2, wherein the diphosphine compound is represented by the formula: R₂P(CH₂)nPR₂ wherein R represents an alkyl group of 1 - 8 carbon atoms, a cycloalkyl group of 6 - 8 carbon atoms, a phenyl group or a tolyl group and n represents an integer of 1 - 6. A process according to claim 18, wherein the diphosphine compound is bis(diphenylphosphino) methane, 1,2-bis(diphenylphosphino)ethane, 1,2-bis(dimethylphosphino)ethane or 1,5-bis(diphenylphosphino)pentane. A process according to claim 19, wherein the diphosphine compound is bis(diphenylphosphino)methane, 1,2-bis(diphenylphosphino)ethane or 1,5-bis(diphenylphosphino)pentane. A process according to claim 2, wherein the amine compound or the diamine compound is added in an amount of 0.01 - 200 mols per one mol of the catalyst metal atom. A process according to claim 2, wherein the amine compound or the diamine compound is added in an amount of 0.01 - 20 mols per one mol of the catalyst metal atom. A process according to claim 2, wherein the phosphine compound or the phosphite compound is added in an amount of 0.01 - 100 mols per one mol of the catalyst metal atom. A process according to claim 2, wherein the phosphine compound or the phosphite compound is added in an amount of 0.01 - 20 mols per one mol of the catalyst metal atom. A process according to claim 2, wherein the diphosphine compound is added in an amount of 0.01 - 10 mols per one mol of the catalyst metal atom. A process according to claim 2, wherein the diphosphine compound is added in an amount of 0.01 - 4 mols per one mol of the catalyst metal atom. A process according to claim 1 or 2, wherein the aqueous alkali solution is aqueous sodium hydroxide solution. A process according to claim 1 or 2, wherein reaction temperature is 20 - 150°C and CO pressure is 1 - 100 atm (1 atm = 1,01325 x 10⁵ Pa). A process according to claim 1 or 2, wherein reaction temperature is 25°C and CO pressure is 1 atm.

Inventors: ISHINO MASARU, NOMURA KOTOHIRO, ISHINO, MASARU, NOMURA, KOTOHIRO
Applicants: SUMITOMO CHEMICAL CO, SUMITOMO CHEMICAL COMPANY, LIMITED
Application year: 1989
Main classification: C07C209
IPC codes: C07C211, C07C253, C07C255, B01J31, C07B61, C07C221, C07C209, C07C213, C07C217, C07C225, C07B43